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Hello,
This short patch series is a snapshot of my proof-of-concept integration
of the generic IOMMU interface with DMA-mapping framework for ARM
architecture and Samsung IOMMU driver.
In this version I rebased the code onto the updated DMA-mapping
framework posted a few minutes ago. Management of io address space have
been moved from genalloc to pure bitmap-based allocator. I've also added
support for mapping a scatterlist with dma_map_sg/dma_unmap_sg. DMA
scatterlist interface turned out to be a bit tricky task. Scatterlist
may describe a set of disjoint buffers that cannot be easily merged
together if they don't start and end on page boundary. In such case we
need to allocate more than one buffer in io address space and map
respective pages. This results in a code that might be bit hard to
understand in the first try.
Right now the code support only 4KiB pages.
The patches have been tested on Samsung Exynos4 platform and FIMC
device. Samsung IOMMU driver has been provided for the reference. It is
still a work-in-progress code, but because of my holidays I wanted to
avoid delaying it further.
Here is the link to the intial version of my ARM & DMA-mapping
integration patches: http://www.spinics.net/lists/linux-mm/msg19856.html
All the patches will be available on the following GIT tree:
git://git.infradead.org/users/kmpark/linux-2.6-samsung dma-mapping-v3
Git web interface:
http://git.infradead.org/users/kmpark/linux-2.6-samsung/shortlog/refs/heads…
Future:
1. Add all missing operations for IOMMU mappings (map_single/page/sync_*)
2. Move sync_* operations into separate function for better code sharing
between iommu and non-iommu dma-mapping code
3. Rebase onto CMA patches and solve the issue with double mapping and
page attributes
4. Add support for pages larger than 4KiB.
Please note that this is very early version of patches, definitely NOT
intended for merging. I just wanted to make sure that the direction is
right and share the code with others that might want to cooperate on
dma-mapping improvements.
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
Patch summary:
Andrzej Pietrasiewicz (1):
ARM: Samsung: update/rewrite Samsung SYSMMU (IOMMU) driver
Marek Szyprowski (1):
ARM: initial proof-of-concept IOMMU mapper for DMA-mapping
arch/arm/Kconfig | 7 +
arch/arm/include/asm/device.h | 4 +
arch/arm/include/asm/dma-iommu.h | 29 +
arch/arm/mach-exynos4/Kconfig | 5 -
arch/arm/mach-exynos4/Makefile | 2 +-
arch/arm/mach-exynos4/clock.c | 47 +-
arch/arm/mach-exynos4/dev-sysmmu.c | 609 +++++++++++------
arch/arm/mach-exynos4/include/mach/irqs.h | 34 +-
arch/arm/mach-exynos4/include/mach/sysmmu.h | 46 --
arch/arm/mm/dma-mapping.c | 504 ++++++++++++++-
arch/arm/mm/vmregion.h | 2 +-
arch/arm/plat-s5p/Kconfig | 21 +-
arch/arm/plat-s5p/include/plat/sysmmu.h | 119 ++--
arch/arm/plat-s5p/sysmmu.c | 855 ++++++++++++++++++------
arch/arm/plat-samsung/include/plat/devs.h | 1 -
arch/arm/plat-samsung/include/plat/fimc-core.h | 25 +
16 files changed, 1724 insertions(+), 586 deletions(-)
create mode 100644 arch/arm/include/asm/dma-iommu.h
delete mode 100644 arch/arm/mach-exynos4/include/mach/sysmmu.h
--
1.7.1.569.g6f426
[Hopefully the last version to linaro-mm-sig before I send it out to
upstream linux lists]
This is the first step in defining a buffer sharing framework.
A new dma_buf buffer object is added, with hooks to allow for easy sharing of
this buffer object across devices.
The framework allows:
- a new buffer-object to be created with fixed size.
- different devices to 'attach' themselves to this buffer, to facilitate
backing storage negotiation, using dma_buf_attach() API.
- association of a file pointer with each user-buffer and associated
allocator-defined operations on that buffer. This operation is called the
'export' operation.
- this exported buffer-object to be shared with the other entity by asking for
its 'file-descriptor (fd)', and sharing the fd across.
- a received fd to get the buffer object back, where it can be accessed using
the associated exporter-defined operations.
- the exporter and user to share the scatterlist using get_scatterlist and
put_scatterlist operations.
Atleast one 'dma_buf_attach()' call is required to be made prior to calling the
get_scatterlist() operation.
Couple of building blocks in get_scatterlist() are added to ease introduction
of sync'ing across exporter and users, and late allocation by the exporter.
mmap() file operation is provided for the associated 'fd', as wrapper over the
optional allocator defined mmap(), to be used by devices that might need one.
Please read documentation added in this patch for more details.
The idea was first mooted at the Linaro memory management mini-summit in
Budapest in May 2011, as part of multiple things needed for a 'unified memory
management framework'. It took a more concrete shape at Linaro memory-management
mini-summit in Cambridge, Aug 2011.
This is based on design suggestions from many people at both the mini-summits,
most notably from Arnd Bergmann <arnd(a)arndb.de>, Rob Clark <rob(a)ti.com> and
Daniel Vetter <daniel(a)ffwll.ch>.
The implementation is inspired from proof-of-concept patch-set from
Tomasz Stanislawski <t.stanislaws(a)samsung.com>, who demonstrated buffer sharing
between two v4l2 devices.
------
v3:
- added dma_buf to dma_attachment and updated {get,put}_scatterlist accordingly.
- added locking mechanism in struct dma_buf, and used around attach-detach APIs.
- dmabuf->ops->attach/detach made optional.
- removed dma_buf_attr_flags and replaced dma_buf_optye with dma_data_direction.
- made dma_buf->ops const in struct dma_buf.
- updated comments for get_scatterlist.
- added documentation.
v2:
- added attach() / detach() dma_buf_ops, and dma_buf_attach(),dma_buf_detach().
- added handling of list of attachment in the dma_buf central API itself.
- corrected copyright information.
v1: initial RFC.
Signed-off-by: Sumit Semwal <sumit.semwal(a)linaro.org>
Signed-off-by: Sumit Semwal <sumit.semwal(a)ti.com>
---
Documentation/dma-buf-sharing.txt | 210 ++++++++++++++++++++++++++++++++
drivers/base/Kconfig | 10 ++
drivers/base/Makefile | 1 +
drivers/base/dma-buf.c | 242 +++++++++++++++++++++++++++++++++++++
include/linux/dma-buf.h | 162 +++++++++++++++++++++++++
5 files changed, 625 insertions(+), 0 deletions(-)
create mode 100644 Documentation/dma-buf-sharing.txt
create mode 100644 drivers/base/dma-buf.c
create mode 100644 include/linux/dma-buf.h
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt
new file mode 100644
index 0000000..4da6644
--- /dev/null
+++ b/Documentation/dma-buf-sharing.txt
@@ -0,0 +1,210 @@
+ DMA Buffer Sharing API Guide
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ Sumit Semwal
+ <sumit dot semwal at linaro dot org>
+ <sumit dot semwal at ti dot com>
+
+This document serves as a guide to device-driver writers on what is the dma-buf
+buffer sharing API, how to use it for exporting and using shared buffers.
+
+Any device driver which wishes to be a part of dma buffer sharing, can do so as
+either the 'exporter' of buffers, or the 'user' of buffers.
+
+Say a driver A wants to use buffers created by driver B, then we call B as the
+exporter, and B as buffer-user.
+
+The exporter
+- implements and manages operations[1] for the buffer
+- allows other users to share the buffer by using dma_buf sharing APIs,
+- manages the details of buffer allocation,
+- decides about the actual backing storage where this allocation happens,
+- takes care of any migration of scatterlist - for all (shared) users of this
+ buffer,
+- optionally, provides mmap capability for drivers that need it.
+
+The buffer-user
+- is one of (many) sharing users of the buffer.
+- doesn't need to worry about how the buffer is allocated, or where.
+- needs a mechanism to get access to the scatterlist that makes up this buffer
+ in memory, mapped into its own address space, so it can access the same area
+ of memory.
+
+
+The dma_buf buffer sharing API usage contains the following steps:
+
+1. Exporter announces that it wishes to export a buffer
+2. Userspace gets the file descriptor associated with the exported buffer, and
+ passes it around to potential buffer-users based on use case
+3. Each buffer-user 'connects' itself to the buffer
+4. When needed, buffer-user requests access to the buffer from exporter
+5. When finished with its use, the buffer-user notifies end-of-dma to exporter
+6. when buffer-user is done using this buffer completely, it 'disconnects'
+ itself from the buffer.
+
+
+1. Exporter's announcement of buffer export
+
+ The buffer exporter announces its wish to export a buffer. In this, it
+ connects its own private buffer data, provides implementation for operations
+ that can be performed on the exported dma_buf, and flags for the file
+ associated with this buffer.
+
+ Interface:
+ struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,
+ int flags)
+
+ If this succeeds, dma_buf_export allocates a dma_buf structure, and returns a
+ pointer to the same. It also associates an anon file with this buffer, so it
+ can be exported. On failure to allocate the dma_buf object, it returns NULL.
+
+2. Userspace gets a handle to pass around to potential buffer-users
+
+ Userspace entity requests for a file-descriptor (fd) which is a handle to the
+ anon file associated with the buffer. It can then share the fd with other
+ drivers and/or processes.
+
+ Interface:
+ int dma_buf_fd(struct dma_buf *dmabuf)
+
+ This API installs an fd for the anon file associated with this buffer;
+ returns either 'fd', or error.
+
+3. Each buffer-user 'connects' itself to the buffer
+
+ Each buffer-user now gets a reference to the buffer, using the fd passed to
+ it.
+
+ Interface:
+ struct dma_buf *dma_buf_get(int fd)
+
+ This API will return a reference to the dma_buf, and increment refcount for
+ it.
+
+ After this, the buffer-user needs to attach its device with the buffer, which
+ helps the exporter to know of device buffer constraints.
+
+ Interface:
+ struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+
+ This API returns reference to an attachment structure, which is then used
+ for scatterlist operations. It will optionally call the 'attach' dma_buf
+ operation, if provided by the exporter.
+
+ The dma-buf sharing framework does the book-keeping bits related to keeping
+ the list of all attachments to a buffer.
+
+Till this stage, the buffer-exporter has the option to choose not to actually
+allocate the backing storage for this buffer, but wait for the first buffer-user
+to request use of buffer for allocation.
+
+
+4. When needed, buffer-user requests access to the buffer
+
+ Whenever a buffer-user wants to use the buffer for any dma, it asks for
+ access to the buffer using dma_buf->ops->get_scatterlist operation. Atleast
+ one attach to the buffer should have happened before get_scatterlist can be
+ called.
+
+ Interface: [member of struct dma_buf_ops]
+ struct scatterlist * (*get_scatterlist)(struct dma_buf_attachment *,
+ enum dma_data_direction,
+ int* nents);
+
+ It is one of the buffer operations that must be implemented by the exporter.
+ It should return the scatterlist for this buffer, mapped into caller's address
+ space.
+
+ If this is being called for the first time, the exporter can now choose to
+ scan through the list of attachments for this buffer, collate the requirements
+ of the attached devices, and choose an appropriate backing storage for the
+ buffer.
+
+ Based on enum dma_data_direction, it might be possible to have multiple users
+ accessing at the same time (for reading, maybe), or any other kind of sharing
+ that the exporter might wish to make available to buffer-users.
+
+
+5. When finished, the buffer-user notifies end-of-dma to exporter
+
+ Once the dma for the current buffer-user is over, it signals 'end-of-dma' to
+ the exporter using the dma_buf->ops->put_scatterlist() operation.
+
+ Interface:
+ void (*put_scatterlist)(struct dma_buf_attachment *, struct scatterlist *,
+ int nents);
+
+ put_scatterlist signifies the end-of-dma for the attachment provided.
+
+
+6. when buffer-user is done using this buffer, it 'disconnects' itself from the
+ buffer.
+
+ After the buffer-user has no more interest in using this buffer, it should
+ disconnect itself from the buffer:
+
+ - it first detaches itself from the buffer.
+
+ Interface:
+ void dma_buf_detach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *dmabuf_attach);
+
+ This API removes the attachment from the list in dmabuf, and optionally calls
+ dma_buf->ops->detach(), if provided by exporter, for any housekeeping bits.
+
+ - Then, the buffer-user returns the buffer reference to exporter.
+
+ Interface:
+ void dma_buf_put(struct dma_buf *dmabuf);
+
+ This API then reduces the refcount for this buffer.
+
+ If, as a result of this call, the refcount becomes 0, the 'release' file
+ operation related to this fd is called. It calls the dmabuf->ops->release()
+ operation in turn, and frees the memory allocated for dmabuf when exported.
+
+NOTES:
+- Importance of attach-detach and {get,put}_scatterlist operation pairs
+ The attach-detach calls allow the exporter to figure out backing-storage
+ constraints for the currently-interested devices. This allows preferential
+ allocation, and/or migration of pages across different types of storage
+ available, if possible.
+
+ Bracketing of dma access with {get,put}_scatterlist operations is essential
+ to allow just-in-time backing of storage, and migration mid-way through a
+ use-case.
+
+- Migration of backing storage if needed
+ After
+ - atleast one get_scatterlist has happened,
+ - and the backing storage has been allocated for this buffer,
+ If another new buffer-user intends to attach itself to this buffer, it might
+ be allowed, if possible for the exporter.
+
+ In case it is allowed by the exporter:
+ if the new buffer-user has stricter 'backing-storage constraints', and the
+ exporter can handle these constraints, the exporter can just stall on the
+ get_scatterlist till all outstanding access is completed (as signalled by
+ put_scatterlist).
+ Once all ongoing access is completed, the exporter could potentially move
+ the buffer to the stricter backing-storage, and then allow further
+ {get,put}_scatterlist operations from any buffer-user from the migrated
+ backing-storage.
+
+ If the exporter cannot fulfill the backing-storage constraints of the new
+ buffer-user device as requested, dma_buf_attach() would return an error to
+ denote non-compatibility of the new buffer-sharing request with the current
+ buffer.
+
+ If the exporter chooses not to allow an attach() operation once a
+ get_scatterlist has been called, it simply returns an error.
+
+- mmap file operation
+ An mmap() file operation is provided for the fd associated with the buffer.
+ If the exporter defines an mmap operation, the mmap() fop calls this to allow
+ mmap for devices that might need it; if not, it returns an error.
+
+References:
+[1] struct dma_buf_ops in include/linux/dma-buf.h
+[2] All interfaces mentioned above defined in include/linux/dma-buf.h
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 21cf46f..07d8095 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -174,4 +174,14 @@ config SYS_HYPERVISOR
source "drivers/base/regmap/Kconfig"
+config DMA_SHARED_BUFFER
+ bool "Buffer framework to be shared between drivers"
+ default n
+ depends on ANON_INODES
+ help
+ This option enables the framework for buffer-sharing between
+ multiple drivers. A buffer is associated with a file using driver
+ APIs extension; the file's descriptor can then be passed on to other
+ driver.
+
endmenu
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 99a375a..d0df046 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
obj-y += power/
obj-$(CONFIG_HAS_DMA) += dma-mapping.o
obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
+obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o
obj-$(CONFIG_ISA) += isa.o
obj-$(CONFIG_FW_LOADER) += firmware_class.o
obj-$(CONFIG_NUMA) += node.o
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
new file mode 100644
index 0000000..58c51a0
--- /dev/null
+++ b/drivers/base/dma-buf.c
@@ -0,0 +1,242 @@
+/*
+ * Framework for buffer objects that can be shared across devices/subsystems.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal(a)ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd(a)arndb.de>, Rob Clark <rob(a)ti.com> and
+ * Daniel Vetter <daniel(a)ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/anon_inodes.h>
+
+static inline int is_dma_buf_file(struct file *);
+
+static int dma_buf_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct dma_buf *dmabuf;
+
+ if (!is_dma_buf_file(file))
+ return -EINVAL;
+
+ dmabuf = file->private_data;
+
+ if (!dmabuf->ops->mmap)
+ return -EINVAL;
+
+ return dmabuf->ops->mmap(dmabuf, vma);
+}
+
+static int dma_buf_release(struct inode *inode, struct file *file)
+{
+ struct dma_buf *dmabuf;
+
+ if (!is_dma_buf_file(file))
+ return -EINVAL;
+
+ dmabuf = file->private_data;
+
+ dmabuf->ops->release(dmabuf);
+ kfree(dmabuf);
+ return 0;
+}
+
+static const struct file_operations dma_buf_fops = {
+ .mmap = dma_buf_mmap,
+ .release = dma_buf_release,
+};
+
+/*
+ * is_dma_buf_file - Check if struct file* is associated with dma_buf
+ */
+static inline int is_dma_buf_file(struct file *file)
+{
+ return file->f_op == &dma_buf_fops;
+}
+
+/**
+ * dma_buf_export - Creates a new dma_buf, and associates an anon file
+ * with this buffer,so it can be exported.
+ * Also connect the allocator specific data and ops to the buffer.
+ *
+ * @priv: [in] Attach private data of allocator to this buffer
+ * @ops: [in] Attach allocator-defined dma buf ops to the new buffer.
+ * @flags: [in] mode flags for the file.
+ *
+ * Returns, on success, a newly created dma_buf object, which wraps the
+ * supplied private data and operations for dma_buf_ops. On failure to
+ * allocate the dma_buf object, it can return NULL.
+ *
+ */
+struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,
+ int flags)
+{
+ struct dma_buf *dmabuf;
+ struct file *file;
+
+ BUG_ON(!priv || !ops);
+
+ dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);
+ if (dmabuf == NULL)
+ return dmabuf;
+
+ dmabuf->priv = priv;
+ dmabuf->ops = ops;
+
+ file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
+
+ dmabuf->file = file;
+
+ mutex_init(&dmabuf->lock);
+ INIT_LIST_HEAD(&dmabuf->attachments);
+
+ return dmabuf;
+}
+EXPORT_SYMBOL(dma_buf_export);
+
+
+/**
+ * dma_buf_fd - returns a file descriptor for the given dma_buf
+ * @dmabuf: [in] pointer to dma_buf for which fd is required.
+ *
+ * On success, returns an associated 'fd'. Else, returns error.
+ */
+int dma_buf_fd(struct dma_buf *dmabuf)
+{
+ int error, fd;
+
+ if (!dmabuf->file)
+ return -EINVAL;
+
+ error = get_unused_fd_flags(0);
+ if (error < 0)
+ return error;
+ fd = error;
+
+ fd_install(fd, dmabuf->file);
+
+ return fd;
+}
+EXPORT_SYMBOL(dma_buf_fd);
+
+/**
+ * dma_buf_get - returns the dma_buf structure related to an fd
+ * @fd: [in] fd associated with the dma_buf to be returned
+ *
+ * On success, returns the dma_buf structure associated with an fd; uses
+ * file's refcounting done by fget to increase refcount. returns ERR_PTR
+ * otherwise.
+ */
+struct dma_buf *dma_buf_get(int fd)
+{
+ struct file *file;
+
+ file = fget(fd);
+
+ if (!file)
+ return ERR_PTR(-EBADF);
+
+ if (!is_dma_buf_file(file)) {
+ fput(file);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return file->private_data;
+}
+EXPORT_SYMBOL(dma_buf_get);
+
+/**
+ * dma_buf_put - decreases refcount of the buffer
+ * @dmabuf: [in] buffer to reduce refcount of
+ *
+ * Uses file's refcounting done implicitly by fput()
+ */
+void dma_buf_put(struct dma_buf *dmabuf)
+{
+ BUG_ON(!dmabuf->file);
+
+ fput(dmabuf->file);
+
+ return;
+}
+EXPORT_SYMBOL(dma_buf_put);
+
+/**
+ * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
+ * calls attach() of dma_buf_ops to allow device-specific attach functionality
+ * @dmabuf: [in] buffer to attach device to.
+ * @dev: [in] device to be attached.
+ *
+ * Returns struct dma_buf_attachment * for this attachment; may return NULL.
+ *
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+{
+ struct dma_buf_attachment *attach;
+ int ret;
+
+ BUG_ON(!dmabuf || !dev);
+
+ mutex_lock(&dmabuf->lock);
+
+ attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);
+ if (attach == NULL)
+ goto err_alloc;
+
+ attach->dev = dev;
+ if (dmabuf->ops->attach) {
+ ret = dmabuf->ops->attach(dmabuf, dev, attach);
+ if (!ret)
+ goto err_attach;
+ }
+ list_add(&attach->node, &dmabuf->attachments);
+
+err_alloc:
+ mutex_unlock(&dmabuf->lock);
+ return attach;
+err_attach:
+ kfree(attach);
+ mutex_unlock(&dmabuf->lock);
+ return ERR_PTR(ret);
+}
+EXPORT_SYMBOL(dma_buf_attach);
+
+/**
+ * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
+ * optionally calls detach() of dma_buf_ops for device-specific detach
+ * @dmabuf: [in] buffer to detach from.
+ * @attach: [in] attachment to be detached; is free'd after this call.
+ *
+ */
+void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
+{
+ BUG_ON(!dmabuf || !attach);
+
+ mutex_lock(&dmabuf->lock);
+ list_del(&attach->node);
+ if (dmabuf->ops->detach)
+ dmabuf->ops->detach(dmabuf, attach);
+
+ kfree(attach);
+ mutex_unlock(&dmabuf->lock);
+ return;
+}
+EXPORT_SYMBOL(dma_buf_detach);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
new file mode 100644
index 0000000..5bdf16a
--- /dev/null
+++ b/include/linux/dma-buf.h
@@ -0,0 +1,162 @@
+/*
+ * Header file for dma buffer sharing framework.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal(a)ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd(a)arndb.de>, Rob Clark <rob(a)ti.com> and
+ * Daniel Vetter <daniel(a)ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __DMA_BUF_H__
+#define __DMA_BUF_H__
+
+#include <linux/file.h>
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/scatterlist.h>
+#include <linux/list.h>
+#include <linux/dma-mapping.h>
+
+struct dma_buf;
+
+/**
+ * struct dma_buf_attachment - holds device-buffer attachment data
+ * @dmabuf: buffer for this attachment.
+ * @dev: device attached to the buffer.
+ * @node: list_head to allow manipulation of list of dma_buf_attachment.
+ * @priv: exporter-specific attachment data.
+ */
+struct dma_buf_attachment {
+ struct dma_buf *dmabuf;
+ struct device *dev;
+ struct list_head node;
+ void *priv;
+};
+
+/**
+ * struct dma_buf_ops - operations possible on struct dma_buf
+ * @create: creates a struct dma_buf of a fixed size. Actual allocation
+ * does not happen here.
+ * @attach: allows different devices to 'attach' themselves to the given
+ * buffer. It might return -EBUSY to signal that backing storage
+ * is already allocated and incompatible with the requirements
+ * of requesting device. [optional]
+ * @detach: detach a given device from this buffer. [optional]
+ * @get_scatterlist: returns list of scatter pages allocated, increases
+ * usecount of the buffer. Requires atleast one attach to be
+ * called before. Returned sg list should already be mapped
+ * into _device_ address space.
+ * @put_scatterlist: decreases usecount of buffer, might deallocate scatter
+ * pages.
+ * @mmap: memory map this buffer - optional.
+ * @release: release this buffer; to be called after the last dma_buf_put.
+ * @sync_sg_for_cpu: sync the sg list for cpu.
+ * @sync_sg_for_device: synch the sg list for device.
+ */
+struct dma_buf_ops {
+ int (*attach)(struct dma_buf *, struct device *,
+ struct dma_buf_attachment *);
+
+ void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
+
+ /* For {get,put}_scatterlist below, any specific buffer attributes
+ * required should get added to device_dma_parameters accessible
+ * via dev->dma_params.
+ */
+ struct scatterlist * (*get_scatterlist)(struct dma_buf_attachment *,
+ enum dma_data_direction,
+ int *nents);
+ void (*put_scatterlist)(struct dma_buf_attachment *,
+ struct scatterlist *,
+ int nents);
+ /* TODO: Add interruptible and interruptible_timeout versions */
+
+ /* allow mmap optionally for devices that need it */
+ int (*mmap)(struct dma_buf *, struct vm_area_struct *);
+ /* after final dma_buf_put() */
+ void (*release)(struct dma_buf *);
+
+ /* allow allocator to take care of cache ops */
+ void (*sync_sg_for_cpu) (struct dma_buf *, struct device *);
+ void (*sync_sg_for_device)(struct dma_buf *, struct device *);
+};
+
+/**
+ * struct dma_buf - shared buffer object
+ * @file: file pointer used for sharing buffers across, and for refcounting.
+ * @attachments: list of dma_buf_attachment that denotes all devices attached.
+ * @ops: dma_buf_ops associated with this buffer object
+ * @priv: user specific private data
+ */
+struct dma_buf {
+ size_t size;
+ struct file *file;
+ struct list_head attachments;
+ const struct dma_buf_ops *ops;
+ /* mutex to serialize list manipulation and other ops */
+ struct mutex lock;
+ void *priv;
+};
+
+#ifdef CONFIG_DMA_SHARED_BUFFER
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev);
+void dma_buf_detach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *dmabuf_attach);
+struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops, int flags);
+int dma_buf_fd(struct dma_buf *dmabuf);
+struct dma_buf *dma_buf_get(int fd);
+void dma_buf_put(struct dma_buf *dmabuf);
+
+#else
+
+static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static inline void dma_buf_detach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *dmabuf_attach)
+{
+ return;
+}
+
+static inline struct dma_buf *dma_buf_export(void *priv,
+ struct dma_buf_ops *ops,
+ int flags)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static inline int dma_buf_fd(struct dma_buf *dmabuf)
+{
+ return -ENODEV;
+}
+
+static inline struct dma_buf *dma_buf_get(int fd)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static inline void dma_buf_put(struct dma_buf *dmabuf)
+{
+ return;
+}
+#endif /* CONFIG_DMA_SHARED_BUFFER */
+
+#endif /* __DMA_BUF_H__ */
--
1.7.4.1
This is the first step in defining a buffer sharing framework.
A new dma_buf buffer object is added, with hooks to allow for easy sharing of
this buffer object across devices.
The framework allows:
- a new buffer-object to be created with fixed size.
- different devices to 'attach' themselves to this buffer, to facilitate
backing storage negotiation, using dma_buf_attach() API.
- association of a file pointer with each user-buffer and associated
allocator-defined operations on that buffer. This operation is called the
'export' operation.
- this exported buffer-object to be shared with the other entity by asking for
its 'file-descriptor (fd)', and sharing the fd across.
- a received fd to get the buffer object back, where it can be accessed using
the associated exporter-defined operations.
- the exporter and importer to share the scatterlist using get_scatterlist and
put_scatterlist operations.
Atleast one 'attach()' call is required to be made prior to calling the
buffer_map() callback.
Couple of building blocks in get_scatterlist() are added to ease introduction
of sync'ing across exporter and importers, and late allocation by the exporter.
Optionally, mmap() file operation is provided for the associated 'fd', as
wrapper over the allocator defined mmap()[optional], to be used by devices that
might need one.
The idea was first mooted at the Linaro memory management mini-summit in
Budapest in May 2011, as part of multiple things needed for a 'unified memory
management framework'. It took a more concrete shape at Linaro memory-management
mini-summit in Cambridge, Aug 2011.
This is based on design suggestions from many people at both the mini-summits,
most notably from Arnd Bergmann <arnd(a)arndb.de>, Rob Clark <rob(a)ti.com> and
Daniel Vetter <daniel(a)ffwll.ch>.
The implementation is inspired from proof-of-concept patch-set from
Tomasz Stanislawski <t.stanislaws(a)samsung.com>, who demonstrated buffer sharing
between two v4l2 devices.
------
v1: initial RFC.
v2:
- added attach() / detach() dma_buf_ops, and dma_buf_attach(),dma_buf_detach().
- added handling of list of attachment in the dma_buf central API itself.
- corrected copyright information.
Signed-off-by: Sumit Semwal <sumit.semwal(a)linaro.org>
Signed-off-by: Sumit Semwal <sumit.semwal(a)ti.com>
---
drivers/base/Kconfig | 10 ++
drivers/base/Makefile | 1 +
drivers/base/dma-buf.c | 224 +++++++++++++++++++++++++++++++++++++++++++++++
include/linux/dma-buf.h | 179 +++++++++++++++++++++++++++++++++++++
4 files changed, 414 insertions(+), 0 deletions(-)
create mode 100644 drivers/base/dma-buf.c
create mode 100644 include/linux/dma-buf.h
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 21cf46f..07d8095 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -174,4 +174,14 @@ config SYS_HYPERVISOR
source "drivers/base/regmap/Kconfig"
+config DMA_SHARED_BUFFER
+ bool "Buffer framework to be shared between drivers"
+ default n
+ depends on ANON_INODES
+ help
+ This option enables the framework for buffer-sharing between
+ multiple drivers. A buffer is associated with a file using driver
+ APIs extension; the file's descriptor can then be passed on to other
+ driver.
+
endmenu
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 99a375a..d0df046 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
obj-y += power/
obj-$(CONFIG_HAS_DMA) += dma-mapping.o
obj-$(CONFIG_HAVE_GENERIC_DMA_COHERENT) += dma-coherent.o
+obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf.o
obj-$(CONFIG_ISA) += isa.o
obj-$(CONFIG_FW_LOADER) += firmware_class.o
obj-$(CONFIG_NUMA) += node.o
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
new file mode 100644
index 0000000..8936da7
--- /dev/null
+++ b/drivers/base/dma-buf.c
@@ -0,0 +1,224 @@
+/*
+ * Framework for buffer objects that can be shared across devices/subsystems.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal(a)ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd(a)arndb.de>, Rob Clark <rob(a)ti.com> and
+ * Daniel Vetter <daniel(a)ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/dma-buf.h>
+#include <linux/anon_inodes.h>
+
+static inline int is_dma_buf_file(struct file *);
+
+static int dma_buf_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct dma_buf *dmabuf;
+
+ if (!is_dma_buf_file(file))
+ return -EINVAL;
+
+ dmabuf = file->private_data;
+
+ if (!dmabuf->ops->mmap)
+ return -EINVAL;
+
+ return dmabuf->ops->mmap(dmabuf, vma);
+}
+
+static int dma_buf_release(struct inode *inode, struct file *file)
+{
+ struct dma_buf *dmabuf;
+
+ if (!is_dma_buf_file(file))
+ return -EINVAL;
+
+ dmabuf = file->private_data;
+
+ dmabuf->ops->release(dmabuf);
+ kfree(dmabuf);
+ return 0;
+}
+
+static const struct file_operations dma_buf_fops = {
+ .mmap = dma_buf_mmap,
+ .release = dma_buf_release,
+};
+
+/*
+ * is_dma_buf_file - Check if struct file* is associated with dma_buf
+ */
+static inline int is_dma_buf_file(struct file *file)
+{
+ return file->f_op == &dma_buf_fops;
+}
+
+/**
+ * dma_buf_export - Creates a new dma_buf, and associates an anon file
+ * with this buffer,so it can be exported.
+ * Also connect the allocator specific data and ops to the buffer.
+ *
+ * @priv: [in] Attach private data of allocator to this buffer
+ * @ops: [in] Attach allocator-defined dma buf ops to the new buffer.
+ * @flags: [in] mode flags for the file.
+ *
+ * Returns, on success, a newly created dma_buf object, which wraps the
+ * supplied private data and operations for dma_buf_ops. On failure to
+ * allocate the dma_buf object, it can return NULL.
+ *
+ */
+struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops,
+ int flags)
+{
+ struct dma_buf *dmabuf;
+ struct file *file;
+
+ BUG_ON(!priv || !ops);
+
+ dmabuf = kzalloc(sizeof(struct dma_buf), GFP_KERNEL);
+ if (dmabuf == NULL)
+ return dmabuf;
+
+ dmabuf->priv = priv;
+ dmabuf->ops = ops;
+
+ file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
+
+ dmabuf->file = file;
+
+ INIT_LIST_HEAD(&dmabuf->attachments);
+
+ return dmabuf;
+}
+EXPORT_SYMBOL(dma_buf_export);
+
+
+/**
+ * dma_buf_fd - returns a file descriptor for the given dma_buf
+ * @dmabuf: [in] pointer to dma_buf for which fd is required.
+ *
+ * On success, returns an associated 'fd'. Else, returns error.
+ */
+int dma_buf_fd(struct dma_buf *dmabuf)
+{
+ int error, fd;
+
+ if (!dmabuf->file)
+ return -EINVAL;
+
+ error = get_unused_fd_flags(0);
+ if (error < 0)
+ return error;
+ fd = error;
+
+ fd_install(fd, dmabuf->file);
+
+ return fd;
+}
+EXPORT_SYMBOL(dma_buf_fd);
+
+/**
+ * dma_buf_get - returns the dma_buf structure related to an fd
+ * @fd: [in] fd associated with the dma_buf to be returned
+ *
+ * On success, returns the dma_buf structure associated with an fd; uses
+ * file's refcounting done by fget to increase refcount. returns ERR_PTR
+ * otherwise.
+ */
+struct dma_buf *dma_buf_get(int fd)
+{
+ struct file *file;
+
+ file = fget(fd);
+
+ if (!file)
+ return ERR_PTR(-EBADF);
+
+ if (!is_dma_buf_file(file)) {
+ fput(file);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return file->private_data;
+}
+EXPORT_SYMBOL(dma_buf_get);
+
+/**
+ * dma_buf_put - decreases refcount of the buffer
+ * @dmabuf: [in] buffer to reduce refcount of
+ *
+ * Uses file's refcounting done implicitly by fput()
+ */
+void dma_buf_put(struct dma_buf *dmabuf)
+{
+ BUG_ON(!dmabuf->file);
+
+ fput(dmabuf->file);
+
+ return;
+}
+EXPORT_SYMBOL(dma_buf_put);
+
+/**
+ * dma_buf_attach - Add the device to dma_buf's attachments list; calls the
+ * attach() of dma_buf_ops to allow device-specific attach functionality
+ * @dmabuf: [in] buffer to attach device to.
+ * @dev: [in] device to be attached.
+ *
+ * Returns struct dma_buf_attachment * for this attachment; may return NULL.
+ *
+ */
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+{
+ struct dma_buf_attachment *attach;
+
+ BUG_ON(!dmabuf || !dev);
+
+ attach = kzalloc(sizeof(struct dma_buf_attachment), GFP_KERNEL);
+ if (attach == NULL)
+ return attach;
+
+ dmabuf->ops->attach(dmabuf, dev, attach);
+ list_add(&attach->node, &dmabuf->attachments);
+
+ return attach;
+}
+EXPORT_SYMBOL(dma_buf_attach);
+
+/**
+ * dma_buf_detach - Remove the given attachment from dmabuf's attachments list;
+ * calls detach() of dma_buf_ops for device-specific detach
+ * @dmabuf: [in] buffer to detach from.
+ * @attach: [in] attachment to be detached; is free'd after this call.
+ *
+ */
+void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
+{
+ BUG_ON(!dmabuf || !attach);
+
+ list_del(&attach->node);
+ dmabuf->ops->detach(dmabuf, attach);
+
+ kfree(attach);
+ return;
+}
+EXPORT_SYMBOL(dma_buf_detach);
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
new file mode 100644
index 0000000..2894b45
--- /dev/null
+++ b/include/linux/dma-buf.h
@@ -0,0 +1,179 @@
+/*
+ * Header file for dma buffer sharing framework.
+ *
+ * Copyright(C) 2011 Linaro Limited. All rights reserved.
+ * Author: Sumit Semwal <sumit.semwal(a)ti.com>
+ *
+ * Many thanks to linaro-mm-sig list, and specially
+ * Arnd Bergmann <arnd(a)arndb.de>, Rob Clark <rob(a)ti.com> and
+ * Daniel Vetter <daniel(a)ffwll.ch> for their support in creation and
+ * refining of this idea.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __DMA_BUF_H__
+#define __DMA_BUF_H__
+
+#include <linux/file.h>
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/scatterlist.h>
+#include <linux/list.h>
+
+struct dma_buf;
+
+/**
+ * enum dma_buf_optype - Used to denote the operation for which
+ * get_scatterlist() is called. This will help in implementing a wait(op)
+ * for sync'ing.
+ * @DMA_BUF_OP_READ: read operation will be done on this scatterlist
+ * @DMA_BUF_OP_WRITE: write operation will be done on this scatterlist
+ */
+enum dma_buf_optype {
+ DMA_BUF_OP_READ = (1 << 0),
+ DMA_BUF_OP_WRITE = (1 << 1),
+ DMA_BUF_OP_MAX,
+};
+
+/**
+ * enum dma_buf_attr_flags - Defines the attributes for this buffer. This
+ * can allow 'late backing of buffer' based on first get_scatterlist() call.
+ * @DMA_BUF_ATTR_CONTIG: Contiguous buffer
+ * @DMA_BUF_ATTR_DISCONTIG: Discontiguous buffer
+ * @DMA_BUF_ATTR_CUSTOM: Platform specific buffer; should evolve into some
+ * attributes that define buffers on given specific platform
+ */
+enum dma_buf_attr_flags {
+ DMA_BUF_ATTR_CONTIG,
+ DMA_BUF_ATTR_DISCONTIG,
+ DMA_BUF_ATTR_CUSTOM,
+ DMA_BUF_ATTR_MAX,
+};
+
+/**
+ * struct dma_buf_attachment - holds device-buffer attachment data
+ * @node: list_head to allow manipulation of list of dma_buf_attachment.
+ * @dev: device attached to the buffer.
+ * @priv: exporter-specific attachment data.
+ */
+struct dma_buf_attachment {
+ struct list_head node;
+ struct device *dev;
+ void *priv;
+};
+
+/**
+ * struct dma_buf_ops - operations possible on struct dma_buf
+ * @create: creates a struct dma_buf of a fixed size. Actual allocation
+ * does not happen here.
+ * @attach: allows different devices to 'attach' themselves to the given
+ * buffer. It might return -EBUSY to signal that backing storage
+ * is already allocated and incompatible with the requirements
+ * of requesting device.
+ * @detach: detach a given device from this buffer.
+ * @get_scatterlist: returns list of scatter pages allocated, increases
+ * usecount of the buffer. Requires atleast one attach to be
+ * called before.
+ * @put_scatterlist: decreases usecount of buffer, might deallocate scatter
+ * pages.
+ * @mmap: memory map this buffer - optional.
+ * @release: release this buffer; to be called after the last dma_buf_put.
+ * @sync_sg_for_cpu: sync the sg list for cpu.
+ * @sync_sg_for_device: synch the sg list for device.
+ */
+struct dma_buf_ops {
+ void (*attach)(struct dma_buf *, struct device *,
+ struct dma_buf_attachment *);
+
+ void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
+
+ struct scatterlist * (*get_scatterlist)(struct dma_buf *,
+ struct dma_buf_attachment *,
+ enum dma_buf_optype,
+ enum dma_buf_attr_flags);
+ void (*put_scatterlist)(struct dma_buf *, struct dma_buf_attachment *,
+ struct scatterlist *);
+
+ /* allow mmap optionally for devices that need it */
+ int (*mmap)(struct dma_buf *, struct vm_area_struct *);
+ /* after final dma_buf_put() */
+ void (*release)(struct dma_buf *);
+
+ /* allow allocator to take care of cache ops */
+ void (*sync_sg_for_cpu) (struct dma_buf *, struct device *);
+ void (*sync_sg_for_device)(struct dma_buf *, struct device *);
+};
+
+/**
+ * struct dma_buf - shared buffer object
+ * @file: file pointer used for sharing buffers across, and for refcounting.
+ * @attachments: list of dma_buf_attachment that denotes all devices attached.
+ * @ops: dma_buf_ops associated with this buffer object
+ * @priv: user specific private data
+ */
+struct dma_buf {
+ size_t size;
+ struct file *file;
+ struct list_head attachments;
+ struct dma_buf_ops *ops;
+ void *priv;
+};
+
+#ifdef CONFIG_DMA_SHARED_BUFFER
+struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev);
+void dma_buf_detach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *dmabuf_attach);
+struct dma_buf *dma_buf_export(void *priv, struct dma_buf_ops *ops, int flags);
+int dma_buf_fd(struct dma_buf *dmabuf);
+struct dma_buf *dma_buf_get(int fd);
+void dma_buf_put(struct dma_buf *dmabuf);
+
+#else
+
+static inline struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
+ struct device *dev)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static inline void dma_buf_detach(struct dma_buf *dmabuf,
+ struct dma_buf_attachment *dmabuf_attach)
+{
+ return;
+}
+
+static inline struct dma_buf *dma_buf_export(void *priv,
+ struct dma_buf_ops *ops,
+ int flags)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static inline int dma_buf_fd(struct dma_buf *dmabuf)
+{
+ return -ENODEV;
+}
+
+static inline struct dma_buf *dma_buf_get(int fd)
+{
+ return ERR_PTR(-ENODEV);
+}
+
+static inline void dma_buf_put(struct dma_buf *dmabuf)
+{
+ return;
+}
+#endif /* CONFIG_DMA_SHARED_BUFFER */
+
+#endif /* __DMA_BUF_H__ */
--
1.7.4.1
Hi all,
As a result of the outcomes of the last face-to-face sessions in
Cambourne in August, I've been putting together a set of topic
branches that reflect the current state of all the efforts of the work
that's been going on. In general, I will be preparing a set of topic
branches for each monthly component releases that we do in Linaro, but
I am certainly open to additional "checkpoints" if folks feel that
there is a piece of work that is significant enough to push out
mid-cycle. As a rule, the overall Linaro releases happen on the last
Thursday of the month, with the component releases happening the
Thursday before that to allow for sane release management. This means
that the component releases for 2011.09 effectively went out this past
Thursday (2011-09-22). Here's what is included there:
http://git.linaro.org/gitweb?p=people/jessebarker/linaro-mm-sig/linux-2.6.g…
cma-v15: Marek Szyprowski's CMA v15 patchset based on v3.1-rc2
(current rc when the patchset went out).
omapdrm: Rob Clark's DRM/KMS driver for OMAP4 based on v3.1-rc6. It
also includes CMA v15, which is enabled by the OMAP driver along with
a couple of other for-next patchsets required to support the DRM
driver.
dma-buf-v2: Sumit Semwal's struct dma_buf v2 proposal based on v3.1-rc6
Please let me know if you encounter problems with any of this, or have
suggestions on how to improve the ease of access for this work (apart
from moving it off of git.linaro.org :-). The goal here is to offer a
single access point to all of this great work to generate better
feedback and ensure that the solutions are robust and upstreamable.
cheers,
Jesse
Hello everyone,
This is yet another round of Contiguous Memory Allocator patches. I hope
that I've managed to resolve all the items discussed during the Memory
Management summit at Linaro Meeting in Budapest and pointed later on
mailing lists. The goal is to integrate it as tight as possible with
other kernel subsystems (like memory management and dma-mapping) and
finally merge to mainline.
Previous version introduced integration with DMA-mapping subsystem for
ARM architecture. In this version I've cleaned up it even more and
prepared for easier integration on other than ARM architectures. I've
also rebased all the code onto latest v3.0-rc6 kernel.
A few words for these who see CMA for the first time:
The Contiguous Memory Allocator (CMA) makes it possible for device
drivers to allocate big contiguous chunks of memory after the system
has booted.
The main difference from the similar frameworks is the fact that CMA
allows to transparently reuse memory region reserved for the big
chunk allocation as a system memory, so no memory is wasted when no
big chunk is allocated. Once the alloc request is issued, the
framework will migrate system pages to create a required big chunk of
physically contiguous memory.
For more information you can refer to nice LWN article:
http://lwn.net/Articles/447405/ and links to previous versions
of CMA framework.
The CMA framework has been initially developed by Michal Nazarewicz
at Samsung Poland R&D Center. Since version 9, I've taken over the
development, because Michal has left the company.
The current version of CMA is a set of helper functions for DMA mapping
framework that handles allocation of contiguous memory blocks. The
difference between this patchset and Kamezawa's alloc_contig_pages()
are:
1. alloc_contig_pages() requires MAX_ORDER alignment of allocations
which may be unsuitable for embeded systems where a few MiBs are
required.
Lack of the requirement on the alignment means that several threads
might try to access the same pageblock/page. To prevent this from
happening CMA uses a mutex so that only one allocating/releasing
function may run at one point.
2. CMA may use its own migratetype (MIGRATE_CMA) which behaves
similarly to ZONE_MOVABLE but can be put in arbitrary places.
This is required for us since we need to define two disjoint memory
ranges inside system RAM. (ie. in two memory banks (do not confuse
with nodes)).
3. alloc_contig_pages() scans memory in search for range that could be
migrated. CMA on the other hand maintains its own allocator to
decide where to allocate memory for device drivers and then tries
to migrate pages from that part if needed. This is not strictly
required but I somehow feel it might be faster.
The integration with ARM DMA-mapping subsystem is quite straightforward.
Once cma context is available alloc_pages() can be replaced by
dma_alloc_from_contiguous() call.
Current version have been tested on Samsung S5PC110 based Goni machine
and s5p-fimc V4L2 driver. The driver itself uses videobuf2 dma-contig
memory allocator, which in turn relies on dma_alloc_coherent() from
DMA-mapping subsystem. By integrating CMA with DMA-mapping we managed to
get this driver working with CMA without any single change required in
the driver or videobuf2-dma-contig allocator.
TODO:
- resolve double-mapping issues with ARMv6+ and coherent memory
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
Links to previous versions of the patchset:
v10: <http://www.spinics.net/lists/linux-mm/msg20761.html>
v9: <http://article.gmane.org/gmane.linux.kernel.mm/60787>
v8: <http://article.gmane.org/gmane.linux.kernel.mm/56855>
v7: <http://article.gmane.org/gmane.linux.kernel.mm/55626>
v6: <http://article.gmane.org/gmane.linux.kernel.mm/55626>
v5: (intentionally left out as CMA v5 was identical to CMA v4)
v4: <http://article.gmane.org/gmane.linux.kernel.mm/52010>
v3: <http://article.gmane.org/gmane.linux.kernel.mm/51573>
v2: <http://article.gmane.org/gmane.linux.kernel.mm/50986>
v1: <http://article.gmane.org/gmane.linux.kernel.mm/50669>
Changelog:
v11:
1. Removed genalloc usage and replaced it with direct calls to
bitmap_* functions, dropped patches that are not needed
anymore (genalloc extensions)
2. Moved all contiguous area management code from mm/cma.c
to drivers/base/dma-contiguous.c
3. Renamed cm_alloc/free to dma_alloc/release_from_contiguous
4. Introduced global, system wide (default) contiguous area
configured with kernel config and kernel cmdline parameters
5. Simplified initialization to just one function:
dma_declare_contiguous()
6. Added example of device private memory contiguous area
v10:
1. Rebased onto 3.0-rc2 and resolved all conflicts
2. Simplified CMA to be just a pure memory allocator, for use
with platfrom/bus specific subsystems, like dma-mapping.
Removed all device specific functions are calls.
3. Integrated with ARM DMA-mapping subsystem.
4. Code cleanup here and there.
5. Removed private context support.
v9: 1. Rebased onto 2.6.39-rc1 and resolved all conflicts
2. Fixed a bunch of nasty bugs that happened when the allocation
failed (mainly kernel oops due to NULL ptr dereference).
3. Introduced testing code: cma-regions compatibility layer and
videobuf2-cma memory allocator module.
v8: 1. The alloc_contig_range() function has now been separated from
CMA and put in page_allocator.c. This function tries to
migrate all LRU pages in specified range and then allocate the
range using alloc_contig_freed_pages().
2. Support for MIGRATE_CMA has been separated from the CMA code.
I have not tested if CMA works with ZONE_MOVABLE but I see no
reasons why it shouldn't.
3. I have added a @private argument when creating CMA contexts so
that one can reserve memory and not share it with the rest of
the system. This way, CMA acts only as allocation algorithm.
v7: 1. A lot of functionality that handled driver->allocator_context
mapping has been removed from the patchset. This is not to say
that this code is not needed, it's just not worth posting
everything in one patchset.
Currently, CMA is "just" an allocator. It uses it's own
migratetype (MIGRATE_CMA) for defining ranges of pageblokcs
which behave just like ZONE_MOVABLE but dispite the latter can
be put in arbitrary places.
2. The migration code that was introduced in the previous version
actually started working.
v6: 1. Most importantly, v6 introduces support for memory migration.
The implementation is not yet complete though.
Migration support means that when CMA is not using memory
reserved for it, page allocator can allocate pages from it.
When CMA wants to use the memory, the pages have to be moved
and/or evicted as to make room for CMA.
To make it possible it must be guaranteed that only movable and
reclaimable pages are allocated in CMA controlled regions.
This is done by introducing a MIGRATE_CMA migrate type that
guarantees exactly that.
Some of the migration code is "borrowed" from Kamezawa
Hiroyuki's alloc_contig_pages() implementation. The main
difference is that thanks to MIGRATE_CMA migrate type CMA
assumes that memory controlled by CMA are is always movable or
reclaimable so that it makes allocation decisions regardless of
the whether some pages are actually allocated and migrates them
if needed.
The most interesting patches from the patchset that implement
the functionality are:
09/13: mm: alloc_contig_free_pages() added
10/13: mm: MIGRATE_CMA migration type added
11/13: mm: MIGRATE_CMA isolation functions added
12/13: mm: cma: Migration support added [wip]
Currently, kernel panics in some situations which I am trying
to investigate.
2. cma_pin() and cma_unpin() functions has been added (after
a conversation with Johan Mossberg). The idea is that whenever
hardware does not use the memory (no transaction is on) the
chunk can be moved around. This would allow defragmentation to
be implemented if desired. No defragmentation algorithm is
provided at this time.
3. Sysfs support has been replaced with debugfs. I always felt
unsure about the sysfs interface and when Greg KH pointed it
out I finally got to rewrite it to debugfs.
v5: (intentionally left out as CMA v5 was identical to CMA v4)
v4: 1. The "asterisk" flag has been removed in favour of requiring
that platform will provide a "*=<regions>" rule in the map
attribute.
2. The terminology has been changed slightly renaming "kind" to
"type" of memory. In the previous revisions, the documentation
indicated that device drivers define memory kinds and now,
v3: 1. The command line parameters have been removed (and moved to
a separate patch, the fourth one). As a consequence, the
cma_set_defaults() function has been changed -- it no longer
accepts a string with list of regions but an array of regions.
2. The "asterisk" attribute has been removed. Now, each region
has an "asterisk" flag which lets one specify whether this
region should by considered "asterisk" region.
3. SysFS support has been moved to a separate patch (the third one
in the series) and now also includes list of regions.
v2: 1. The "cma_map" command line have been removed. In exchange,
a SysFS entry has been created under kernel/mm/contiguous.
The intended way of specifying the attributes is
a cma_set_defaults() function called by platform initialisation
code. "regions" attribute (the string specified by "cma"
command line parameter) can be overwritten with command line
parameter; the other attributes can be changed during run-time
using the SysFS entries.
2. The behaviour of the "map" attribute has been modified
slightly. Currently, if no rule matches given device it is
assigned regions specified by the "asterisk" attribute. It is
by default built from the region names given in "regions"
attribute.
3. Devices can register private regions as well as regions that
can be shared but are not reserved using standard CMA
mechanisms. A private region has no name and can be accessed
only by devices that have the pointer to it.
4. The way allocators are registered has changed. Currently,
a cma_allocator_register() function is used for that purpose.
Moreover, allocators are attached to regions the first time
memory is registered from the region or when allocator is
registered which means that allocators can be dynamic modules
that are loaded after the kernel booted (of course, it won't be
possible to allocate a chunk of memory from a region if
allocator is not loaded).
5. Index of new functions:
+static inline dma_addr_t __must_check
+cma_alloc_from(const char *regions, size_t size,
+ dma_addr_t alignment)
+static inline int
+cma_info_about(struct cma_info *info, const const char *regions)
+int __must_check cma_region_register(struct cma_region *reg);
+dma_addr_t __must_check
+cma_alloc_from_region(struct cma_region *reg,
+ size_t size, dma_addr_t alignment);
+static inline dma_addr_t __must_check
+cma_alloc_from(const char *regions,
+ size_t size, dma_addr_t alignment);
+int cma_allocator_register(struct cma_allocator *alloc);
Patches in this patchset:
mm: move some functions from memory_hotplug.c to page_isolation.c
mm: alloc_contig_freed_pages() added
Code "stolen" from Kamezawa. The first patch just moves code
around and the second provide function for "allocates" already
freed memory.
mm: alloc_contig_range() added
This is what Kamezawa asked: a function that tries to migrate all
pages from given range and then use alloc_contig_freed_pages()
(defined by the previous commit) to allocate those pages.
mm: MIGRATE_CMA migration type added
mm: MIGRATE_CMA isolation functions added
Introduction of the new migratetype and support for it in CMA.
MIGRATE_CMA works similar to ZONE_MOVABLE expect almost any
memory range can be marked as one.
mm: cma: Contiguous Memory Allocator added
The code CMA code. Manages CMA contexts and performs memory
allocations.
ARM: integrate CMA with dma-mapping subsystem
Main client of CMA frame work. CMA serves as a alloc_pages()
replacement.
ARM: S5PV210: example of CMA private area for FIMC device on Goni board
Example of platform/board specific code that creates cma
context and assigns it to particular device.
Patch summary:
KAMEZAWA Hiroyuki (2):
mm: move some functions from memory_hotplug.c to page_isolation.c
mm: alloc_contig_freed_pages() added
Marek Szyprowski (3):
drivers: add Contiguous Memory Allocator
ARM: integrate CMA with dma-mapping subsystem
ARM: S5PV210: example of CMA private area for FIMC device on Goni
board
Michal Nazarewicz (3):
mm: alloc_contig_range() added
mm: MIGRATE_CMA migration type added
mm: MIGRATE_CMA isolation functions added
arch/arm/Kconfig | 1 +
arch/arm/include/asm/device.h | 3 +
arch/arm/include/asm/dma-mapping.h | 20 ++
arch/arm/mach-s5pv210/Kconfig | 1 +
arch/arm/mach-s5pv210/mach-goni.c | 7 +
arch/arm/mm/dma-mapping.c | 51 ++++--
arch/arm/mm/init.c | 3 +
drivers/base/Kconfig | 77 ++++++++
drivers/base/Makefile | 1 +
drivers/base/dma-contiguous.c | 367 ++++++++++++++++++++++++++++++++++++
include/linux/dma-contiguous.h | 104 ++++++++++
include/linux/mmzone.h | 43 ++++-
include/linux/page-isolation.h | 54 ++++--
mm/Kconfig | 8 +-
mm/compaction.c | 10 +
mm/memory_hotplug.c | 111 -----------
mm/page_alloc.c | 293 ++++++++++++++++++++++++++---
mm/page_isolation.c | 130 ++++++++++++-
18 files changed, 1112 insertions(+), 172 deletions(-)
create mode 100644 drivers/base/dma-contiguous.c
create mode 100644 include/linux/dma-contiguous.h
--
1.7.1.569.g6f426
Hello,
This is a snapshot of my work-in-progress on DMA-mapping framework
redesign. All these works are a preparation for adding support for IOMMU
controllers.
DMA-mapping patches have been rebased onto Linux v3.1-rc4 kernel, what
required resolving a bunch of confilcts in the code. The patches have
been heavily tested and all bugs found in the initial version have been
fixed.
Here is the link to the initial version of the DMA-mapping redesign patches:
http://www.spinics.net/lists/linux-mm/msg21241.html
TODO:
- merge the patches with CMA patches and respective changes in
DMA-mapping framework
- start the discussion about chaning alloc_coherent into alloc_attrs in
dma_map_ops structure.
The proof-of-concept IOMMU mapper for DMA-mapping will follow. In next 2
weeks I will be on holidays, so I decided not to delay these patch
anymore longer.
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
Patch summary:
Marek Szyprowski (7):
ARM: dma-mapping: remove offset parameter to prepare for generic
dma_ops
ARM: dma-mapping: use asm-generic/dma-mapping-common.h
ARM: dma-mapping: implement dma sg methods on top of any generic dma
ops
ARM: dma-mapping: move all dma bounce code to separate dma ops
structure
ARM: dma-mapping: remove redundant code and cleanup
common: dma-mapping: change alloc/free_coherent method to more
generic alloc/free_attrs
ARM: dma-mapping: use alloc, mmap, free from dma_ops
arch/arm/Kconfig | 1 +
arch/arm/common/dmabounce.c | 78 ++++++--
arch/arm/include/asm/device.h | 1 +
arch/arm/include/asm/dma-mapping.h | 401 ++++++++++--------------------------
arch/arm/mm/dma-mapping.c | 269 +++++++++++++-----------
include/linux/dma-attrs.h | 1 +
include/linux/dma-mapping.h | 13 +-
7 files changed, 325 insertions(+), 439 deletions(-)
--
1.7.1.569.g6f426
Hello again,
This is yet another round of Contiguous Memory Allocator patches. Now I
implemented all the ideas that has been discussed during Linaro Sprint
meeting.
This version provides a solution for complete integration of CMA to DMA
mapping subsystem on ARM architecture. The issue caused by double dma
pages mapping and possible aliasing in coherent memory mapping has been
finally resolved, both for GFP_ATOMIC case (allocations comes from
coherent memory pool) and non-GFP_ATOMIC case (allocations comes from
CMA managed areas).
For coherent, nommu, ARMv4 and ARMv5 systems the current DMA-mapping
implementation has been kept.
For ARMv6+ systems, CMA has been enabled and a special pool of coherent
memory for atomic allocations has been created. The size of this pool
defaults to CONSISTEN_DMA_SIZE/8, but can be changed with coherent_pool
kernel parameter (if really required).
All atomic allocations are served from this pool. I've did a little
simplification here, because there is no separate pool for writecombine
memory - such requests are also served from coherent pool. I don't think
that such simplification is a problem here - I found no driver that use
dma_alloc_writecombine with GFP_ATOMIC flags.
All non-atomic allocation are served from CMA area. Kernel mapping is
updated to reflect required memory attributes changes. This is possible
because during early boot, all CMA area are remapped with 4KiB pages in
kernel low-memory.
This version have been tested on Samsung S5PC110 based Goni machine and
Exynos4 UniversalC210 board with various V4L2 multimedia drivers.
Coherent atomic allocations has been tested by manually enabling the dma
bounce for the s3c-sdhci device.
All patches are prepared for Linux Kernel v3.1-rc2.
A few words for these who see CMA for the first time:
The Contiguous Memory Allocator (CMA) makes it possible for device
drivers to allocate big contiguous chunks of memory after the system
has booted.
The main difference from the similar frameworks is the fact that CMA
allows to transparently reuse memory region reserved for the big
chunk allocation as a system memory, so no memory is wasted when no
big chunk is allocated. Once the alloc request is issued, the
framework will migrate system pages to create a required big chunk of
physically contiguous memory.
For more information you can refer to nice LWN articles:
http://lwn.net/Articles/447405/ and http://lwn.net/Articles/450286/
as well as links to previous versions of the CMA framework.
The CMA framework has been initially developed by Michal Nazarewicz
at Samsung Poland R&D Center. Since version 9, I've taken over the
development, because Michal has left the company.
TODO (optional):
- implement support for contiguous memory areas placed in HIGHMEM zone
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
Links to previous versions of the patchset:
v14: <http://www.spinics.net/lists/linux-media/msg36536.html>
v13: (internal, intentionally not released)
v12: <http://www.spinics.net/lists/linux-media/msg35674.html>
v11: <http://www.spinics.net/lists/linux-mm/msg21868.html>
v10: <http://www.spinics.net/lists/linux-mm/msg20761.html>
v9: <http://article.gmane.org/gmane.linux.kernel.mm/60787>
v8: <http://article.gmane.org/gmane.linux.kernel.mm/56855>
v7: <http://article.gmane.org/gmane.linux.kernel.mm/55626>
v6: <http://article.gmane.org/gmane.linux.kernel.mm/55626>
v5: (intentionally left out as CMA v5 was identical to CMA v4)
v4: <http://article.gmane.org/gmane.linux.kernel.mm/52010>
v3: <http://article.gmane.org/gmane.linux.kernel.mm/51573>
v2: <http://article.gmane.org/gmane.linux.kernel.mm/50986>
v1: <http://article.gmane.org/gmane.linux.kernel.mm/50669>
Changelog:
v15:
1. fixed calculation of the total memory after activating CMA area (was
broken from v12)
2. more code cleanup in drivers/base/dma-contiguous.c
3. added address limit for default CMA area
4. rewrote ARM DMA integration:
- removed "ARM: DMA: steal memory for DMA coherent mappings" patch
- kept current DMA mapping implementation for coherent, nommu and
ARMv4/ARMv5 systems
- enabled CMA for all ARMv6+ systems
- added separate, small pool for coherent atomic allocations, defaults
to CONSISTENT_DMA_SIZE/8, but can be changed with kernel parameter
coherent_pool=[size]
v14:
1. Merged with "ARM: DMA: steal memory for DMA coherent mappings"
patch, added support for GFP_ATOMIC allocations.
2. Added checks for NULL device pointer
v13: (internal, intentionally not released)
v12:
1. Fixed 2 nasty bugs in dma-contiguous allocator:
- alignment argument was not passed correctly
- range for dma_release_from_contiguous was not checked correctly
2. Added support for architecture specfic dma_contiguous_early_fixup()
function
3. CMA and DMA-mapping integration for ARM architechture has been
rewritten to take care of the memory aliasing issue that might
happen for newer ARM CPUs (mapping of the same pages with different
cache attributes is forbidden). TODO: add support for GFP_ATOMIC
allocations basing on the "ARM: DMA: steal memory for DMA coherent
mappings" patch and implement support for contiguous memory areas
that are placed in HIGHMEM zone
v11:
1. Removed genalloc usage and replaced it with direct calls to
bitmap_* functions, dropped patches that are not needed
anymore (genalloc extensions)
2. Moved all contiguous area management code from mm/cma.c
to drivers/base/dma-contiguous.c
3. Renamed cm_alloc/free to dma_alloc/release_from_contiguous
4. Introduced global, system wide (default) contiguous area
configured with kernel config and kernel cmdline parameters
5. Simplified initialization to just one function:
dma_declare_contiguous()
6. Added example of device private memory contiguous area
v10:
1. Rebased onto 3.0-rc2 and resolved all conflicts
2. Simplified CMA to be just a pure memory allocator, for use
with platfrom/bus specific subsystems, like dma-mapping.
Removed all device specific functions are calls.
3. Integrated with ARM DMA-mapping subsystem.
4. Code cleanup here and there.
5. Removed private context support.
v9: 1. Rebased onto 2.6.39-rc1 and resolved all conflicts
2. Fixed a bunch of nasty bugs that happened when the allocation
failed (mainly kernel oops due to NULL ptr dereference).
3. Introduced testing code: cma-regions compatibility layer and
videobuf2-cma memory allocator module.
v8: 1. The alloc_contig_range() function has now been separated from
CMA and put in page_allocator.c. This function tries to
migrate all LRU pages in specified range and then allocate the
range using alloc_contig_freed_pages().
2. Support for MIGRATE_CMA has been separated from the CMA code.
I have not tested if CMA works with ZONE_MOVABLE but I see no
reasons why it shouldn't.
3. I have added a @private argument when creating CMA contexts so
that one can reserve memory and not share it with the rest of
the system. This way, CMA acts only as allocation algorithm.
v7: 1. A lot of functionality that handled driver->allocator_context
mapping has been removed from the patchset. This is not to say
that this code is not needed, it's just not worth posting
everything in one patchset.
Currently, CMA is "just" an allocator. It uses it's own
migratetype (MIGRATE_CMA) for defining ranges of pageblokcs
which behave just like ZONE_MOVABLE but dispite the latter can
be put in arbitrary places.
2. The migration code that was introduced in the previous version
actually started working.
v6: 1. Most importantly, v6 introduces support for memory migration.
The implementation is not yet complete though.
Migration support means that when CMA is not using memory
reserved for it, page allocator can allocate pages from it.
When CMA wants to use the memory, the pages have to be moved
and/or evicted as to make room for CMA.
To make it possible it must be guaranteed that only movable and
reclaimable pages are allocated in CMA controlled regions.
This is done by introducing a MIGRATE_CMA migrate type that
guarantees exactly that.
Some of the migration code is "borrowed" from Kamezawa
Hiroyuki's alloc_contig_pages() implementation. The main
difference is that thanks to MIGRATE_CMA migrate type CMA
assumes that memory controlled by CMA are is always movable or
reclaimable so that it makes allocation decisions regardless of
the whether some pages are actually allocated and migrates them
if needed.
The most interesting patches from the patchset that implement
the functionality are:
09/13: mm: alloc_contig_free_pages() added
10/13: mm: MIGRATE_CMA migration type added
11/13: mm: MIGRATE_CMA isolation functions added
12/13: mm: cma: Migration support added [wip]
Currently, kernel panics in some situations which I am trying
to investigate.
2. cma_pin() and cma_unpin() functions has been added (after
a conversation with Johan Mossberg). The idea is that whenever
hardware does not use the memory (no transaction is on) the
chunk can be moved around. This would allow defragmentation to
be implemented if desired. No defragmentation algorithm is
provided at this time.
3. Sysfs support has been replaced with debugfs. I always felt
unsure about the sysfs interface and when Greg KH pointed it
out I finally got to rewrite it to debugfs.
v5: (intentionally left out as CMA v5 was identical to CMA v4)
v4: 1. The "asterisk" flag has been removed in favour of requiring
that platform will provide a "*=<regions>" rule in the map
attribute.
2. The terminology has been changed slightly renaming "kind" to
"type" of memory. In the previous revisions, the documentation
indicated that device drivers define memory kinds and now,
v3: 1. The command line parameters have been removed (and moved to
a separate patch, the fourth one). As a consequence, the
cma_set_defaults() function has been changed -- it no longer
accepts a string with list of regions but an array of regions.
2. The "asterisk" attribute has been removed. Now, each region
has an "asterisk" flag which lets one specify whether this
region should by considered "asterisk" region.
3. SysFS support has been moved to a separate patch (the third one
in the series) and now also includes list of regions.
v2: 1. The "cma_map" command line have been removed. In exchange,
a SysFS entry has been created under kernel/mm/contiguous.
The intended way of specifying the attributes is
a cma_set_defaults() function called by platform initialisation
code. "regions" attribute (the string specified by "cma"
command line parameter) can be overwritten with command line
parameter; the other attributes can be changed during run-time
using the SysFS entries.
2. The behaviour of the "map" attribute has been modified
slightly. Currently, if no rule matches given device it is
assigned regions specified by the "asterisk" attribute. It is
by default built from the region names given in "regions"
attribute.
3. Devices can register private regions as well as regions that
can be shared but are not reserved using standard CMA
mechanisms. A private region has no name and can be accessed
only by devices that have the pointer to it.
4. The way allocators are registered has changed. Currently,
a cma_allocator_register() function is used for that purpose.
Moreover, allocators are attached to regions the first time
memory is registered from the region or when allocator is
registered which means that allocators can be dynamic modules
that are loaded after the kernel booted (of course, it won't be
possible to allocate a chunk of memory from a region if
allocator is not loaded).
5. Index of new functions:
+static inline dma_addr_t __must_check
+cma_alloc_from(const char *regions, size_t size,
+ dma_addr_t alignment)
+static inline int
+cma_info_about(struct cma_info *info, const const char *regions)
+int __must_check cma_region_register(struct cma_region *reg);
+dma_addr_t __must_check
+cma_alloc_from_region(struct cma_region *reg,
+ size_t size, dma_addr_t alignment);
+static inline dma_addr_t __must_check
+cma_alloc_from(const char *regions,
+ size_t size, dma_addr_t alignment);
+int cma_allocator_register(struct cma_allocator *alloc);
Patches in this patchset:
mm: move some functions from memory_hotplug.c to page_isolation.c
mm: alloc_contig_freed_pages() added
Code "stolen" from Kamezawa. The first patch just moves code
around and the second provide function for "allocates" already
freed memory.
mm: alloc_contig_range() added
This is what Kamezawa asked: a function that tries to migrate all
pages from given range and then use alloc_contig_freed_pages()
(defined by the previous commit) to allocate those pages.
mm: MIGRATE_CMA migration type added
mm: MIGRATE_CMA isolation functions added
Introduction of the new migratetype and support for it in CMA.
MIGRATE_CMA works similar to ZONE_MOVABLE expect almost any
memory range can be marked as one.
mm: cma: Contiguous Memory Allocator added
The code CMA code. Manages CMA contexts and performs memory
allocations.
ARM: integrate CMA with dma-mapping subsystem
Main client of CMA frame work. CMA serves as a alloc_pages()
replacement.
ARM: S5PV210: example of CMA private area for FIMC device on Goni board
Example of platform/board specific code that creates cma
context and assigns it to particular device.
Patch summary:
KAMEZAWA Hiroyuki (2):
mm: move some functions from memory_hotplug.c to page_isolation.c
mm: alloc_contig_freed_pages() added
Marek Szyprowski (3):
drivers: add Contiguous Memory Allocator
ARM: integrate CMA with DMA-mapping subsystem
ARM: S5PV210: example of CMA private area for FIMC device on Goni
board
Michal Nazarewicz (3):
mm: alloc_contig_range() added
mm: MIGRATE_CMA migration type added
mm: MIGRATE_CMA isolation functions added
arch/Kconfig | 3 +
arch/arm/Kconfig | 2 +
arch/arm/include/asm/device.h | 3 +
arch/arm/include/asm/dma-contiguous.h | 33 +++
arch/arm/include/asm/mach/map.h | 1 +
arch/arm/mach-s5pv210/mach-goni.c | 4 +
arch/arm/mm/dma-mapping.c | 362 +++++++++++++++++++++++++------
arch/arm/mm/init.c | 8 +
arch/arm/mm/mm.h | 3 +
arch/arm/mm/mmu.c | 29 ++-
drivers/base/Kconfig | 79 +++++++
drivers/base/Makefile | 1 +
drivers/base/dma-contiguous.c | 386 +++++++++++++++++++++++++++++++++
include/linux/dma-contiguous.h | 102 +++++++++
include/linux/mmzone.h | 41 +++-
include/linux/page-isolation.h | 51 ++++-
mm/Kconfig | 8 +-
mm/compaction.c | 10 +
mm/memory_hotplug.c | 111 ----------
mm/page_alloc.c | 287 ++++++++++++++++++++++--
mm/page_isolation.c | 129 +++++++++++-
21 files changed, 1417 insertions(+), 236 deletions(-)
create mode 100644 arch/arm/include/asm/dma-contiguous.h
create mode 100644 drivers/base/dma-contiguous.c
create mode 100644 include/linux/dma-contiguous.h
--
1.7.1.569.g6f426
On Wed, Sep 14, 2011 at 2:57 AM, Thomas Hellstrom <thomas(a)shipmail.org> wrote:
>>>>>>>>>
>>>>>>>>> +static struct drm_ioctl_desc samsung_ioctls[] = {
>>>>>>>>> + DRM_IOCTL_DEF_DRV(SAMSUNG_GEM_CREATE,
>>>>>>>>> samsung_drm_gem_create_ioctl,
>>>>>>>>> + DRM_UNLOCKED | DRM_AUTH),
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> Hi!
>>>>>>>>
>>>>>>>> With reference my previous security comment.
>>>>>>>>
>>>>>>>> Let's say you have a compromised video player running as a DRM
>>>>>>>> client, that
>>>>>>>> tries to repeatedly allocate huge GEM buffers...
>>>>>>>>
>>>>>>>> What will happen when all DMA memory is exhausted? Will this cause
>>>>>>>> other
>>>>>>>> device drivers to see an OOM, or only DRM?
>>>>>>>>
>>>>>>>> The old DRI model basically allowed any authorized DRI client to
>>>>>>>> exhaust
>>>>>>>> video ram or AGP memory, but never system memory. Newer DRI drivers
>>>>>>>> typically only allow DRI masters to do that.
>>>>>>>> as
>>>>>>>>
>>>>>>>> I don't think an authorized DRI client should be able to easily
>>>>>>>>
>>>>>
>>>>> exhaust
>>>>>
>>>>>>>>
>>>>>>>> resources (DMA memory) used by other device drivers causing them to
>>>>>>>> fail.
>>>>>>>>
>>>>>>>
>>>>>>> I'm not entirely sure what else can be done, other than have a
>>>>>>> threshold on max MB allocatable of buffer memory..
>>>>>>>
>>>>>>
>>>>>> Yes, I think that's what needs to be done, and that threshold should
>>>>>> be low enough to keep other device drivers running in the worst
>>>>>> allocation case.
>>>>>>
>>>>>>
>>>>>>>
>>>>>>> In the samsung driver case, he is only allocating scanout memory
>>>>>>>
>>>
>>> from
>>>
>>>>>>>
>>>>>>> CMA, so the limit will be the CMA region size.. beyond that you
>>>>>>>
>>>
>>> can't
>>>
>>>>>>>
>>>>>>> get physically contiguous memory. So I think this driver is safe.
>>>>>>>
>>>>>>
>>>>>> It's not really what well-behaved user-space drivers do that should
>>>>>>
>>>
>>> be
>>>
>>>>>>
>>>>>> a concern, but what compromized application *might* do that is a
>>>>>>
>>>>
>>>> concern.
>>>>
>>>>>
>>>>> Hmm. I might have missed your point here. If the buffer allocation
>>>>>
>>>
>>> ioctl
>>>
>>>>>
>>>>> only allows allocating CMA memory, then I agree the driver fits the old
>>>>> DRI security model, as long as no other devices on the platform will
>>>>> ever use CMA.
>>>>>
>>>>> But in that case, there really should be a way for the driver to say
>>>>> "Hey, all CMA memory on this system is mine", in the same way
>>>>> traditional video drivers can claim the VRAM PCI resource.
>>>>>
>>>>>
>>>>
>>>> CMA could reserve memory region for a specific driver so DRM Client
>>>>
>>>
>>> could
>>>
>>>>
>>>> request memory allocation from only the region.
>>>>
>>>>
>>>>>
>>>>> This is to avoid the possibility that future drivers that need CMA will
>>>>> be vulnerable to DOS-attacks from ill-behaved DRI clients.
>>>>>
>>>>>
>>>>
>>>> Thomas, if any application has root authority for ill-purpose then isn't
>>>>
>>>
>>> it
>>>
>>>>
>>>> possible to be vulnerable to DOS-attacks? I think DRM_AUTH means root
>>>> authority. I know DRM Framework gives any root application DRM_AUTH
>>>> authority for compatibility.
>>>>
>>>
>>> DRM_AUTH just means that the client has authenticated w/ X11 (meaning
>>> that it has permission to connect to x server)..
>>>
>>>
>>
>> Yes, I understood so. but see drm_open_helper() of drm_fops.c file please.
>> in this function, you can see a line below.
>> /* for compatibility root is always authenticated */
>> priv->authenticated = capable(CAP_SYS_ADMIN)
>>
>> I think the code above says that any application with root permission is
>> authenticated.
>>
>>
>
> Yes, that is true. A root client may be assumed to have AUTH permissions,
> but the inverse does not hold, meaning that an AUTH client may *not* be
> assumed to have root permissions. I think there is a ROOT_ONLY ioctl flag
> for that.
>
> The problem I'm seeing compared to other drivers is the following:
>
> Imagine for example that you have a disc driver that allocates temporary
> memory out of the same DMA pool as the DRM driver.
>
> Now you have a video player that is a DRM client. It contains a security
> flaw and is compromized by somebody trying to play a specially crafted video
> stream. The video player starts to allocate gem buffers until it receives an
> -ENOMEM. Then it stops allocating and does nothing.
>
> Now the system tries an important disc access (paging for example). This
> fails, because the video player has exhausted all DMA memory and the disc
> driver fails to allocate.
>
> The system is dead.
>
> The point is:
>
> If there is a chance that other drivers will use the same DMA/CMA pool as
> the DRM driver, DRM must leave enough DMA/CMA memory for those drivers to
> work.
ah, ok, I get your point
> The difference compared to other drm drivers:
>
> There are other drm drivers that work the same way, with a static allocator.
> For example "via" and "sis". But those drivers completely claim the
> resources they are using. Nobody else is expected to use VRAM / AGP.
>
> In the Samsung case, it's not clear to me whether the DMA/CMA pool *can* be
> shared with other devices.
> If it is, IMHO you must implement an allocation limit in DRM, if not, the
> driver should probably be safe.
It is possible to create a device private CMA pool.. although OTOH it
might be desirable to let some other drivers (like v4l2) use buffers
from the same pool..
I'm not entirely sure what will happen w/ dma_alloc_coherent, etc, if
the global CMA pool is exhausted.
Marek? I guess you know what would happen?
BR,
-R
> Thanks,
> Thomas
