Linaro-mm-sig

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7031 discussions

[PATCH] staging: android: ion: fix err_cast.cocci warnings

by kbuild test robot

From: kbuild test robot <lkp(a)intel.com> drivers/staging/android/ion/ion.c:427:9-16: WARNING: ERR_CAST can be used with buffer Use ERR_CAST inlined function instead of ERR_PTR(PTR_ERR(...)) Generated by: scripts/coccinelle/api/err_cast.cocci Fixes: d51f182d188a ("staging: android: ion: refactory ion_alloc for kernel driver use") CC: Zeng Tao <prime.zeng(a)hisilicon.com> Signed-off-by: kbuild test robot <lkp(a)intel.com> --- url: https://github.com/0day-ci/linux/commits/Zeng-Tao/staging-android-ion-refac… ion.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/staging/android/ion/ion.c +++ b/drivers/staging/android/ion/ion.c @@ -424,7 +424,7 @@ struct dma_buf *ion_alloc(size_t len, un return ERR_PTR(-ENODEV); if (IS_ERR(buffer)) - return ERR_PTR(PTR_ERR(buffer)); + return ERR_CAST(buffer); exp_info.ops = &dma_buf_ops; exp_info.size = buffer->size;

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH] staging: android: ion: refactory ion_alloc for kernel driver use

by kbuild test robot

Hi Zeng, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on staging/staging-testing] [also build test WARNING on v5.1-rc2 next-20190329] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/Zeng-Tao/staging-android-ion-refac… coccinelle warnings: (new ones prefixed by >>) >> drivers/staging/android/ion/ion.c:427:9-16: WARNING: ERR_CAST can be used with buffer Please review and possibly fold the followup patch. --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH] staging: android: ion: refactory ion_alloc for kernel driver use

by Greg Kroah-Hartman

On Sat, Mar 30, 2019 at 02:32:35AM +0000, Zengtao (B) wrote: > >-----Original Message----- > >From: Greg Kroah-Hartman [mailto:gregkh@linuxfoundation.org] > >Sent: Saturday, March 30, 2019 12:04 AM > >To: Zengtao (B) <prime.zeng(a)hisilicon.com> > >Cc: labbott(a)redhat.com; sumit.semwal(a)linaro.org; > >devel(a)driverdev.osuosl.org; Todd Kjos <tkjos(a)android.com>; > >linux-kernel(a)vger.kernel.org; dri-devel(a)lists.freedesktop.org; > >linaro-mm-sig(a)lists.linaro.org; Arve Hjønnevåg <arve(a)android.com>; > >Joel Fernandes <joel(a)joelfernandes.org>; Martijn Coenen > ><maco(a)android.com>; Christian Brauner <christian(a)brauner.io> > >Subject: Re: [PATCH] staging: android: ion: refactory ion_alloc for kernel > >driver use > > > >On Sat, Mar 30, 2019 at 02:40:16AM +0800, Zeng Tao wrote: > >> There are two reasons for this patch: > >> 1. There are some potential requirements for ion_alloc in kernel > >> space, some media drivers need to allocate media buffers from ion > >> instead of buddy or dma framework, this is more convient and clean > >> very for media drivers. And In that case, ion is the only media buffer > >> provider, it's more easier to maintain. > > > >As this really is just DMA, what is wrong with the existing dma framework > >that makes it hard to use? You have seen all of the changes recently to it, > >right? > > The current dma framework is powerful enough(to me, and more complex ^_^) > , CMA, IOMMU are all integrated, it's good. But buffer sharing, statistics, debug, > are not so friendly for media drivers(each driver has to do all, but duplicate jobs). Then go add statistics and debugging to the dma code so that everyone benefits! thanks, greg k-h

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH] staging: android: ion: refactory ion_alloc for kernel driver use

by Greg Kroah-Hartman

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH] staging: android: ion: refactory ion_alloc for kernel driver use

by Greg Kroah-Hartman

On Sat, Mar 30, 2019 at 02:40:16AM +0800, Zeng Tao wrote: > There are two reasons for this patch: > 1. There are some potential requirements for ion_alloc in kernel space, > some media drivers need to allocate media buffers from ion instead of > buddy or dma framework, this is more convient and clean very for media > drivers. And In that case, ion is the only media buffer provider, it's > more easier to maintain. > 2. Fd is only needed by user processes, not the kernel space, so dma_buf > should be returned instead of fd for kernel space, and dma_buf_fd should > be called only for userspace api. > > Signed-off-by: Zeng Tao <prime.zeng(a)hisilicon.com> > --- > drivers/staging/android/ion/ion.c | 32 +++++++++++++++++--------------- > 1 file changed, 17 insertions(+), 15 deletions(-) > > diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c > index 92c2914..e93fb49 100644 > --- a/drivers/staging/android/ion/ion.c > +++ b/drivers/staging/android/ion/ion.c > @@ -387,13 +387,13 @@ static const struct dma_buf_ops dma_buf_ops = { > .unmap = ion_dma_buf_kunmap, > }; > > -static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > +struct dma_buf *ion_alloc(size_t len, unsigned int heap_id_mask, > + unsigned int flags) > { > struct ion_device *dev = internal_dev; > struct ion_buffer *buffer = NULL; > struct ion_heap *heap; > DEFINE_DMA_BUF_EXPORT_INFO(exp_info); > - int fd; > struct dma_buf *dmabuf; > > pr_debug("%s: len %zu heap_id_mask %u flags %x\n", __func__, > @@ -407,7 +407,7 @@ static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > len = PAGE_ALIGN(len); > > if (!len) > - return -EINVAL; > + return ERR_PTR(-EINVAL); > > down_read(&dev->lock); > plist_for_each_entry(heap, &dev->heaps, node) { > @@ -421,10 +421,10 @@ static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > up_read(&dev->lock); > > if (!buffer) > - return -ENODEV; > + return ERR_PTR(-ENODEV); > > if (IS_ERR(buffer)) > - return PTR_ERR(buffer); > + return ERR_PTR(PTR_ERR(buffer)); > > exp_info.ops = &dma_buf_ops; > exp_info.size = buffer->size; > @@ -432,17 +432,12 @@ static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > exp_info.priv = buffer; > > dmabuf = dma_buf_export(&exp_info); > - if (IS_ERR(dmabuf)) { > + if (IS_ERR(dmabuf)) > _ion_buffer_destroy(buffer); > - return PTR_ERR(dmabuf); > - } > > - fd = dma_buf_fd(dmabuf, O_CLOEXEC); > - if (fd < 0) > - dma_buf_put(dmabuf); > - > - return fd; > + return dmabuf; > } > +EXPORT_SYMBOL(ion_alloc); If you are going to do this (and personally I'm with Laura in that I don't think you need it) this should be EXPORT_SYMBOL_GPL() please. thanks, greg k-h

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH] staging: android: ion: refactory ion_alloc for kernel driver use

by Laura Abbott

On 3/29/19 11:40 AM, Zeng Tao wrote: > There are two reasons for this patch: > 1. There are some potential requirements for ion_alloc in kernel space, > some media drivers need to allocate media buffers from ion instead of > buddy or dma framework, this is more convient and clean very for media > drivers. And In that case, ion is the only media buffer provider, it's > more easier to maintain. > 2. Fd is only needed by user processes, not the kernel space, so dma_buf > should be returned instead of fd for kernel space, and dma_buf_fd should > be called only for userspace api. > I really want to just NAK this because it doesn't seem like something that's necessary. The purpose of Ion is to provide buffers to userspace because there's no other way for userspace to get access to the memory. The kernel already has other APIs to access the memory. This also complicates the re-work that's been happening where the requirement is only userspace. Can you be more detailed about which media drivers you are referring to and why they can't just use other APIs? > Signed-off-by: Zeng Tao <prime.zeng(a)hisilicon.com> > --- > drivers/staging/android/ion/ion.c | 32 +++++++++++++++++--------------- > 1 file changed, 17 insertions(+), 15 deletions(-) > > diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c > index 92c2914..e93fb49 100644 > --- a/drivers/staging/android/ion/ion.c > +++ b/drivers/staging/android/ion/ion.c > @@ -387,13 +387,13 @@ static const struct dma_buf_ops dma_buf_ops = { > .unmap = ion_dma_buf_kunmap, > }; > > -static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > +struct dma_buf *ion_alloc(size_t len, unsigned int heap_id_mask, > + unsigned int flags) > { > struct ion_device *dev = internal_dev; > struct ion_buffer *buffer = NULL; > struct ion_heap *heap; > DEFINE_DMA_BUF_EXPORT_INFO(exp_info); > - int fd; > struct dma_buf *dmabuf; > > pr_debug("%s: len %zu heap_id_mask %u flags %x\n", __func__, > @@ -407,7 +407,7 @@ static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > len = PAGE_ALIGN(len); > > if (!len) > - return -EINVAL; > + return ERR_PTR(-EINVAL); > > down_read(&dev->lock); > plist_for_each_entry(heap, &dev->heaps, node) { > @@ -421,10 +421,10 @@ static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > up_read(&dev->lock); > > if (!buffer) > - return -ENODEV; > + return ERR_PTR(-ENODEV); > > if (IS_ERR(buffer)) > - return PTR_ERR(buffer); > + return ERR_PTR(PTR_ERR(buffer)); > > exp_info.ops = &dma_buf_ops; > exp_info.size = buffer->size; > @@ -432,17 +432,12 @@ static int ion_alloc(size_t len, unsigned int heap_id_mask, unsigned int flags) > exp_info.priv = buffer; > > dmabuf = dma_buf_export(&exp_info); > - if (IS_ERR(dmabuf)) { > + if (IS_ERR(dmabuf)) > _ion_buffer_destroy(buffer); > - return PTR_ERR(dmabuf); > - } > > - fd = dma_buf_fd(dmabuf, O_CLOEXEC); > - if (fd < 0) > - dma_buf_put(dmabuf); > - > - return fd; > + return dmabuf; > } > +EXPORT_SYMBOL(ion_alloc); > > static int ion_query_heaps(struct ion_heap_query *query) > { > @@ -539,12 +534,19 @@ static long ion_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) > case ION_IOC_ALLOC: > { > int fd; > + struct dma_buf *dmabuf; > > - fd = ion_alloc(data.allocation.len, > + dmabuf = ion_alloc(data.allocation.len, > data.allocation.heap_id_mask, > data.allocation.flags); > - if (fd < 0) > + if (IS_ERR(dmabuf)) > + return PTR_ERR(dmabuf); > + > + fd = dma_buf_fd(dmabuf, O_CLOEXEC); > + if (fd < 0) { > + dma_buf_put(dmabuf); > return fd; > + } > > data.allocation.fd = fd; > >

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH] staging: android: ion: refactory ion_alloc for kernel driver use

by Dan Carpenter

If we're going to export ion_alloc() for other drivers to use then let's make an ion_free() helper function as well. void ion_free(struct dma_buf *dmabuf) { dma_buf_put(dmabuf); } regards, dan carpenter

7 years, 4 months

Re: [Linaro-mm-sig] [PATCH RFC 1/1] uio: Add dma-buf import ioctls

by Daniel Vetter

On Thu, Feb 28, 2019 at 04:18:57PM -0800, Hyun Kwon wrote: > Hi Daniel, > > On Thu, 2019-02-28 at 02:01:46 -0800, Daniel Vetter wrote: > > On Wed, Feb 27, 2019 at 04:36:06PM -0800, Hyun Kwon wrote: > > > Hi Daniel, > > > > > > On Wed, 2019-02-27 at 06:13:45 -0800, Daniel Vetter wrote: > > > > On Tue, Feb 26, 2019 at 11:20 PM Hyun Kwon <hyun.kwon(a)xilinx.com> wrote: > > > > > > > > > > Hi Daniel, > > > > > > > > > > Thanks for the comment. > > > > > > > > > > On Tue, 2019-02-26 at 04:06:13 -0800, Daniel Vetter wrote: > > > > > > On Tue, Feb 26, 2019 at 12:53 PM Greg Kroah-Hartman > > > > > > <gregkh(a)linuxfoundation.org> wrote: > > > > > > > > > > > > > > On Sat, Feb 23, 2019 at 12:28:17PM -0800, Hyun Kwon wrote: > > > > > > > > Add the dmabuf map / unmap interfaces. This allows the user driver > > > > > > > > to be able to import the external dmabuf and use it from user space. > > > > > > > > > > > > > > > > Signed-off-by: Hyun Kwon <hyun.kwon(a)xilinx.com> > > > > > > > > --- > > > > > > > > drivers/uio/Makefile | 2 +- > > > > > > > > drivers/uio/uio.c | 43 +++++++++ > > > > > > > > drivers/uio/uio_dmabuf.c | 210 +++++++++++++++++++++++++++++++++++++++++++ > > > > > > > > drivers/uio/uio_dmabuf.h | 26 ++++++ > > > > > > > > include/uapi/linux/uio/uio.h | 33 +++++++ > > > > > > > > 5 files changed, 313 insertions(+), 1 deletion(-) > > > > > > > > create mode 100644 drivers/uio/uio_dmabuf.c > > > > > > > > create mode 100644 drivers/uio/uio_dmabuf.h > > > > > > > > create mode 100644 include/uapi/linux/uio/uio.h > > > > > > > > > > > > > > > > diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile > > > > > > > > index c285dd2..5da16c7 100644 > > > > > > > > --- a/drivers/uio/Makefile > > > > > > > > +++ b/drivers/uio/Makefile > > > > > > > > @@ -1,5 +1,5 @@ > > [snip] > > > > > > > Frankly looks like a ploy to sidestep review by graphics folks. We'd > > > > > > ask for the userspace first :-) > > > > > > > > > > Please refer to pull request [1]. > > > > > > > > > > For any interest in more details, the libmetal is the abstraction layer > > > > > which provides platform independent APIs. The backend implementation > > > > > can be selected per different platforms: ex, rtos, linux, > > > > > standalone (xilinx),,,. For Linux, it supports UIO / vfio as of now. > > > > > The actual user space drivers sit on top of libmetal. Such drivers can be > > > > > found in [2]. This is why I try to avoid any device specific code in > > > > > Linux kernel. > > > > > > > > > > > > > > > > > Also, exporting dma_addr to userspace is considered a very bad idea. > > > > > > > > > > I agree, hence the RFC to pick some brains. :-) Would it make sense > > > > > if this call doesn't export the physicall address, but instead takes > > > > > only the dmabuf fd and register offsets to be programmed? > > > > > > > > > > > If you want to do this properly, you need a minimal in-kernel memory > > > > > > manager, and those tend to be based on top of drm_gem.c and merged > > > > > > through the gpu tree. The last place where we accidentally leaked a > > > > > > dma addr for gpu buffers was in the fbdev code, and we plugged that > > > > > > one with > > > > > > > > > > Could you please help me understand how having a in-kernel memory manager > > > > > helps? Isn't it just moving same dmabuf import / paddr export functionality > > > > > in different modules: kernel memory manager vs uio. In fact, Xilinx does have > > > > > such memory manager based on drm gem in downstream. But for this time we took > > > > > the approach of implementing this through generic dmabuf allocator, ION, and > > > > > enabling the import capability in the UIO infrastructure instead. > > > > > > > > There's a group of people working on upstreaming a xilinx drm driver > > > > already. Which driver are we talking about? Can you pls provide a link > > > > to that xilinx drm driver? > > > > > > > > > > The one I was pushing [1] is implemented purely for display, and not > > > intended for anything other than that as of now. What I'm refering to above > > > is part of Xilinx FPGA (acceleration) runtime [2]. As far as I know, > > > it's planned to be upstreamed, but not yet started. The Xilinx runtime > > > software has its own in-kernel memory manager based on drm_cma_gem with > > > its own ioctls [3]. > > > > > > Thanks, > > > -hyun > > > > > > [1] https://patchwork.kernel.org/patch/10513001/ > > > [2] https://github.com/Xilinx/XRT > > > [3] https://github.com/Xilinx/XRT/tree/master/src/runtime_src/driver/zynq/drm > > > > I've done a very quick look only, and yes this is kinda what I'd expect. > > Doing a small drm gem driver for an fpga/accelarator that needs lots of > > memories is the right architecture, since at the low level of kernel > > interfaces a gpu really isn't anything else than an accelarater. > > > > And from a very cursory look the gem driver you mentioned (I only scrolled > > through the ioctl handler quickly) looks reasonable. > > Thanks for taking time to look and share input. But still I'd like to > understand why it's more reasonable if the similar ioctl exists with drm > than with uio. Is it because such drm ioctl is vendor specific? We do have quite a pile of shared infrastructure in drm beyond just the vendor specific ioctl. So putting accelerator drivers there makes sense, whether the programming is a GPU, some neural network folder, an FPGA or something else. The one issue is that we require open source userspace together with your driver, since just the accelerator shim in the kernel alone is fairly useless (both for review and for doing anything with it). But there's also some kernel maintainers who disagree and happily take drivers originally written for drm and then rewritten for non-drm for upstream to avoid the drm folks (or at least it very much looks like that, and happens fairly regularly). Cheers, Daniel > > Thanks, > -hyun > > > -Daniel > > > > > > > Thanks, Daniel > > > > > > > > > Thanks, > > > > > -hyun > > > > > > > > > > [1] https://github.com/OpenAMP/libmetal/pull/82/commits/951e2762bd487c98919ad12… > > > > > [2] https://github.com/Xilinx/embeddedsw/tree/master/XilinxProcessorIPLib/drive… > > > > > > > > > > > > > > > > > commit 4be9bd10e22dfc7fc101c5cf5969ef2d3a042d8a (tag: > > > > > > drm-misc-next-fixes-2018-10-03) > > > > > > Author: Neil Armstrong <narmstrong(a)baylibre.com> > > > > > > Date: Fri Sep 28 14:05:55 2018 +0200 > > > > > > > > > > > > drm/fb_helper: Allow leaking fbdev smem_start > > > > > > > > > > > > Together with cuse the above patch should be enough to implement a drm > > > > > > driver entirely in userspace at least. > > > > > > > > > > > > Cheers, Daniel > > > > > > -- > > > > > > Daniel Vetter > > > > > > Software Engineer, Intel Corporation > > > > > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch > > > > > > > > > > > > > > > > -- > > > > Daniel Vetter > > > > Software Engineer, Intel Corporation > > > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

7 years, 5 months

Re: [Linaro-mm-sig] [PATCH 2/4] staging: android: ion: Restrict cache maintenance to dma mapped memory

by Liam Mark

On Fri, 18 Jan 2019, Andrew F. Davis wrote: > On 1/18/19 12:37 PM, Liam Mark wrote: > > The ION begin_cpu_access and end_cpu_access functions use the > > dma_sync_sg_for_cpu and dma_sync_sg_for_device APIs to perform cache > > maintenance. > > > > Currently it is possible to apply cache maintenance, via the > > begin_cpu_access and end_cpu_access APIs, to ION buffers which are not > > dma mapped. > > > > The dma sync sg APIs should not be called on sg lists which have not been > > dma mapped as this can result in cache maintenance being applied to the > > wrong address. If an sg list has not been dma mapped then its dma_address > > field has not been populated, some dma ops such as the swiotlb_dma_ops ops > > use the dma_address field to calculate the address onto which to apply > > cache maintenance. > > > > Also I don’t think we want CMOs to be applied to a buffer which is not > > dma mapped as the memory should already be coherent for access from the > > CPU. Any CMOs required for device access taken care of in the > > dma_buf_map_attachment and dma_buf_unmap_attachment calls. > > So really it only makes sense for begin_cpu_access and end_cpu_access to > > apply CMOs if the buffer is dma mapped. > > > > Fix the ION begin_cpu_access and end_cpu_access functions to only apply > > cache maintenance to buffers which are dma mapped. > > > > Fixes: 2a55e7b5e544 ("staging: android: ion: Call dma_map_sg for syncing and mapping") > > Signed-off-by: Liam Mark <lmark(a)codeaurora.org> > > --- > > drivers/staging/android/ion/ion.c | 26 +++++++++++++++++++++----- > > 1 file changed, 21 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c > > index 6f5afab7c1a1..1fe633a7fdba 100644 > > --- a/drivers/staging/android/ion/ion.c > > +++ b/drivers/staging/android/ion/ion.c > > @@ -210,6 +210,7 @@ struct ion_dma_buf_attachment { > > struct device *dev; > > struct sg_table *table; > > struct list_head list; > > + bool dma_mapped; > > }; > > > > static int ion_dma_buf_attach(struct dma_buf *dmabuf, > > @@ -231,6 +232,7 @@ static int ion_dma_buf_attach(struct dma_buf *dmabuf, > > > > a->table = table; > > a->dev = attachment->dev; > > + a->dma_mapped = false; > > INIT_LIST_HEAD(&a->list); > > > > attachment->priv = a; > > @@ -261,12 +263,18 @@ static struct sg_table *ion_map_dma_buf(struct dma_buf_attachment *attachment, > > { > > struct ion_dma_buf_attachment *a = attachment->priv; > > struct sg_table *table; > > + struct ion_buffer *buffer = attachment->dmabuf->priv; > > > > table = a->table; > > > > + mutex_lock(&buffer->lock); > > if (!dma_map_sg(attachment->dev, table->sgl, table->nents, > > - direction)) > > + direction)) { > > + mutex_unlock(&buffer->lock); > > return ERR_PTR(-ENOMEM); > > + } > > + a->dma_mapped = true; > > + mutex_unlock(&buffer->lock); > > > > return table; > > } > > @@ -275,7 +283,13 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment, > > struct sg_table *table, > > enum dma_data_direction direction) > > { > > + struct ion_dma_buf_attachment *a = attachment->priv; > > + struct ion_buffer *buffer = attachment->dmabuf->priv; > > + > > + mutex_lock(&buffer->lock); > > dma_unmap_sg(attachment->dev, table->sgl, table->nents, direction); > > + a->dma_mapped = false; > > + mutex_unlock(&buffer->lock); > > } > > > > static int ion_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) > > @@ -346,8 +360,9 @@ static int ion_dma_buf_begin_cpu_access(struct dma_buf *dmabuf, > > > > mutex_lock(&buffer->lock); > > list_for_each_entry(a, &buffer->attachments, list) { > > When no devices are attached then buffer->attachments is empty and the > below does not run, so if I understand this patch correctly then what > you are protecting against is CPU access in the window after > dma_buf_attach but before dma_buf_map. > Yes > This is the kind of thing that again makes me think a couple more > ordering requirements on DMA-BUF ops are needed. DMA-BUFs do not require > the backing memory to be allocated until map time, this is why the > dma_address field would still be null as you note in the commit message. > So why should the CPU be performing accesses on a buffer that is not > actually backed yet? > > I can think of two solutions: > > 1) Only allow CPU access (mmap, kmap, {begin,end}_cpu_access) while at > least one device is mapped. > Would be quite limiting to clients. > 2) Treat the CPU access request like the a device map request and > trigger the allocation of backing memory just like if a device map had > come in. > Which is, as you mention pretty much what we have now (though the buffer is allocated even earlier). > I know the current Ion heaps (and most other DMA-BUF exporters) all do > the allocation up front so the memory is already there, but DMA-BUF was > designed with late allocation in mind. I have a use-case I'm working on > that finally exercises this DMA-BUF functionality and I would like to > have it export through ION. This patch doesn't prevent that, but seems > like it is endorsing the the idea that buffers always need to be backed, > even before device attach/map is has occurred. > I didn't interpret the DMA-buf contract as requiring the dma-map to be called in order for a backing store to be provided, I interpreted it as meaning there could be a backing store before the dma-map but at the dma-map call the final backing store configuration would be decided (perhaps involving migrating the memory to the final backing store). I will let the dma-buf experts correct me on that. Limiting userspace clients to not be able to access buffers until after they are dma-mapped seems unfortuntate to me, dma-mapping usually means a change of ownership of the memory from the CPU to the device. So generally while a buffer is dma mapped you have the device access it (though of course it is supported for CPU to access to the buffer while dma mapped) and then once the buffer is dma-unmapped the CPU can access it. This is how the DMA APIs are frequently used, and the changes above make ION align more with the way the DMA APIs are used. Basically when the buffer is not dma-mapped the CPU doesn't need to do any CMOs to access the buffer (and ION ensures not CMOs are applied) but if the CPU does want to access the buffer while it is dma mapped then ION ensures that the appropriate CMOs are applied. It seems like a legitimate uses case to me to allow clients to access the buffer before (and after) dma-mapping, example post processing of buffers. > Either of the above two solutions would need to target the DMA-BUF > framework, > > Sumit, > > Any comment? > > Thanks, > Andrew > > > - dma_sync_sg_for_cpu(a->dev, a->table->sgl, a->table->nents, > > - direction); > > + if (a->dma_mapped) > > + dma_sync_sg_for_cpu(a->dev, a->table->sgl, > > + a->table->nents, direction); > > } > > > > unlock: > > @@ -369,8 +384,9 @@ static int ion_dma_buf_end_cpu_access(struct dma_buf *dmabuf, > > > > mutex_lock(&buffer->lock); > > list_for_each_entry(a, &buffer->attachments, list) { > > - dma_sync_sg_for_device(a->dev, a->table->sgl, a->table->nents, > > - direction); > > + if (a->dma_mapped) > > + dma_sync_sg_for_device(a->dev, a->table->sgl, > > + a->table->nents, direction); > > } > > mutex_unlock(&buffer->lock); > > > > > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

7 years, 5 months

Re: [Linaro-mm-sig] [PATCH RFC 1/1] uio: Add dma-buf import ioctls

by Daniel Vetter

On Wed, Feb 27, 2019 at 04:36:06PM -0800, Hyun Kwon wrote: > Hi Daniel, > > On Wed, 2019-02-27 at 06:13:45 -0800, Daniel Vetter wrote: > > On Tue, Feb 26, 2019 at 11:20 PM Hyun Kwon <hyun.kwon(a)xilinx.com> wrote: > > > > > > Hi Daniel, > > > > > > Thanks for the comment. > > > > > > On Tue, 2019-02-26 at 04:06:13 -0800, Daniel Vetter wrote: > > > > On Tue, Feb 26, 2019 at 12:53 PM Greg Kroah-Hartman > > > > <gregkh(a)linuxfoundation.org> wrote: > > > > > > > > > > On Sat, Feb 23, 2019 at 12:28:17PM -0800, Hyun Kwon wrote: > > > > > > Add the dmabuf map / unmap interfaces. This allows the user driver > > > > > > to be able to import the external dmabuf and use it from user space. > > > > > > > > > > > > Signed-off-by: Hyun Kwon <hyun.kwon(a)xilinx.com> > > > > > > --- > > > > > > drivers/uio/Makefile | 2 +- > > > > > > drivers/uio/uio.c | 43 +++++++++ > > > > > > drivers/uio/uio_dmabuf.c | 210 +++++++++++++++++++++++++++++++++++++++++++ > > > > > > drivers/uio/uio_dmabuf.h | 26 ++++++ > > > > > > include/uapi/linux/uio/uio.h | 33 +++++++ > > > > > > 5 files changed, 313 insertions(+), 1 deletion(-) > > > > > > create mode 100644 drivers/uio/uio_dmabuf.c > > > > > > create mode 100644 drivers/uio/uio_dmabuf.h > > > > > > create mode 100644 include/uapi/linux/uio/uio.h > > > > > > > > > > > > diff --git a/drivers/uio/Makefile b/drivers/uio/Makefile > > > > > > index c285dd2..5da16c7 100644 > > > > > > --- a/drivers/uio/Makefile > > > > > > +++ b/drivers/uio/Makefile > > > > > > @@ -1,5 +1,5 @@ > > > > > > # SPDX-License-Identifier: GPL-2.0 > > > > > > -obj-$(CONFIG_UIO) += uio.o > > > > > > +obj-$(CONFIG_UIO) += uio.o uio_dmabuf.o > > > > > > obj-$(CONFIG_UIO_CIF) += uio_cif.o > > > > > > obj-$(CONFIG_UIO_PDRV_GENIRQ) += uio_pdrv_genirq.o > > > > > > obj-$(CONFIG_UIO_DMEM_GENIRQ) += uio_dmem_genirq.o > > > > > > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c > > > > > > index 1313422..6841f98 100644 > > > > > > --- a/drivers/uio/uio.c > > > > > > +++ b/drivers/uio/uio.c > > > > > > @@ -24,6 +24,12 @@ > > > > > > #include <linux/kobject.h> > > > > > > #include <linux/cdev.h> > > > > > > #include <linux/uio_driver.h> > > > > > > +#include <linux/list.h> > > > > > > +#include <linux/mutex.h> > > > > > > + > > > > > > +#include <uapi/linux/uio/uio.h> > > > > > > + > > > > > > +#include "uio_dmabuf.h" > > > > > > > > > > > > #define UIO_MAX_DEVICES (1U << MINORBITS) > > > > > > > > > > > > @@ -454,6 +460,8 @@ static irqreturn_t uio_interrupt(int irq, void *dev_id) > > > > > > struct uio_listener { > > > > > > struct uio_device *dev; > > > > > > s32 event_count; > > > > > > + struct list_head dbufs; > > > > > > + struct mutex dbufs_lock; /* protect @dbufs */ > > > > > > }; > > > > > > > > > > > > static int uio_open(struct inode *inode, struct file *filep) > > > > > > @@ -500,6 +508,9 @@ static int uio_open(struct inode *inode, struct file *filep) > > > > > > if (ret) > > > > > > goto err_infoopen; > > > > > > > > > > > > + INIT_LIST_HEAD(&listener->dbufs); > > > > > > + mutex_init(&listener->dbufs_lock); > > > > > > + > > > > > > return 0; > > > > > > > > > > > > err_infoopen: > > > > > > @@ -529,6 +540,10 @@ static int uio_release(struct inode *inode, struct file *filep) > > > > > > struct uio_listener *listener = filep->private_data; > > > > > > struct uio_device *idev = listener->dev; > > > > > > > > > > > > + ret = uio_dmabuf_cleanup(idev, &listener->dbufs, &listener->dbufs_lock); > > > > > > + if (ret) > > > > > > + dev_err(&idev->dev, "failed to clean up the dma bufs\n"); > > > > > > + > > > > > > mutex_lock(&idev->info_lock); > > > > > > if (idev->info && idev->info->release) > > > > > > ret = idev->info->release(idev->info, inode); > > > > > > @@ -652,6 +667,33 @@ static ssize_t uio_write(struct file *filep, const char __user *buf, > > > > > > return retval ? retval : sizeof(s32); > > > > > > } > > > > > > > > > > > > +static long uio_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) > > > > > > > > > > We have resisted adding a uio ioctl for a long time, can't you do this > > > > > through sysfs somehow? > > > > > > > > > > A meta-comment about your ioctl structure: > > > > > > > > > > > +#define UIO_DMABUF_DIR_BIDIR 1 > > > > > > +#define UIO_DMABUF_DIR_TO_DEV 2 > > > > > > +#define UIO_DMABUF_DIR_FROM_DEV 3 > > > > > > +#define UIO_DMABUF_DIR_NONE 4 > > > > > > > > > > enumerated type? > > > > > > > > > > > + > > > > > > +struct uio_dmabuf_args { > > > > > > + __s32 dbuf_fd; > > > > > > + __u64 dma_addr; > > > > > > + __u64 size; > > > > > > + __u32 dir; > > > > > > > > > > Why the odd alignment? Are you sure this is the best packing for such a > > > > > structure? > > > > > > > > > > Why is dbuf_fd __s32? dir can be __u8, right? > > > > > > > > > > I don't know that dma layer very well, it would be good to get some > > > > > review from others to see if this really is even a viable thing to do. > > > > > The fd handling seems a bit "odd" here, but maybe I just do not > > > > > understand it. > > > > > > > > Frankly looks like a ploy to sidestep review by graphics folks. We'd > > > > ask for the userspace first :-) > > > > > > Please refer to pull request [1]. > > > > > > For any interest in more details, the libmetal is the abstraction layer > > > which provides platform independent APIs. The backend implementation > > > can be selected per different platforms: ex, rtos, linux, > > > standalone (xilinx),,,. For Linux, it supports UIO / vfio as of now. > > > The actual user space drivers sit on top of libmetal. Such drivers can be > > > found in [2]. This is why I try to avoid any device specific code in > > > Linux kernel. > > > > > > > > > > > Also, exporting dma_addr to userspace is considered a very bad idea. > > > > > > I agree, hence the RFC to pick some brains. :-) Would it make sense > > > if this call doesn't export the physicall address, but instead takes > > > only the dmabuf fd and register offsets to be programmed? > > > > > > > If you want to do this properly, you need a minimal in-kernel memory > > > > manager, and those tend to be based on top of drm_gem.c and merged > > > > through the gpu tree. The last place where we accidentally leaked a > > > > dma addr for gpu buffers was in the fbdev code, and we plugged that > > > > one with > > > > > > Could you please help me understand how having a in-kernel memory manager > > > helps? Isn't it just moving same dmabuf import / paddr export functionality > > > in different modules: kernel memory manager vs uio. In fact, Xilinx does have > > > such memory manager based on drm gem in downstream. But for this time we took > > > the approach of implementing this through generic dmabuf allocator, ION, and > > > enabling the import capability in the UIO infrastructure instead. > > > > There's a group of people working on upstreaming a xilinx drm driver > > already. Which driver are we talking about? Can you pls provide a link > > to that xilinx drm driver? > > > > The one I was pushing [1] is implemented purely for display, and not > intended for anything other than that as of now. What I'm refering to above > is part of Xilinx FPGA (acceleration) runtime [2]. As far as I know, > it's planned to be upstreamed, but not yet started. The Xilinx runtime > software has its own in-kernel memory manager based on drm_cma_gem with > its own ioctls [3]. > > Thanks, > -hyun > > [1] https://patchwork.kernel.org/patch/10513001/ > [2] https://github.com/Xilinx/XRT > [3] https://github.com/Xilinx/XRT/tree/master/src/runtime_src/driver/zynq/drm I've done a very quick look only, and yes this is kinda what I'd expect. Doing a small drm gem driver for an fpga/accelarator that needs lots of memories is the right architecture, since at the low level of kernel interfaces a gpu really isn't anything else than an accelarater. And from a very cursory look the gem driver you mentioned (I only scrolled through the ioctl handler quickly) looks reasonable. -Daniel > > > Thanks, Daniel > > > > > Thanks, > > > -hyun > > > > > > [1] https://github.com/OpenAMP/libmetal/pull/82/commits/951e2762bd487c98919ad12… > > > [2] https://github.com/Xilinx/embeddedsw/tree/master/XilinxProcessorIPLib/drive… > > > > > > > > > > > commit 4be9bd10e22dfc7fc101c5cf5969ef2d3a042d8a (tag: > > > > drm-misc-next-fixes-2018-10-03) > > > > Author: Neil Armstrong <narmstrong(a)baylibre.com> > > > > Date: Fri Sep 28 14:05:55 2018 +0200 > > > > > > > > drm/fb_helper: Allow leaking fbdev smem_start > > > > > > > > Together with cuse the above patch should be enough to implement a drm > > > > driver entirely in userspace at least. > > > > > > > > Cheers, Daniel > > > > -- > > > > Daniel Vetter > > > > Software Engineer, Intel Corporation > > > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch > > > > > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

7 years, 5 months

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