dma-buf has become a way to safely acquire a handle to non-struct page memory that can still have lifetime controlled by the exporter. Notably RDMA can now import dma-buf FDs and build them into MRs which allows for PCI P2P operations. Extend this to allow vfio-pci to export MMIO memory from PCI device BARs.
The patch design loosely follows the pattern in commit db1a8dd916aa ("habanalabs: add support for dma-buf exporter") except this does not support pinning.
Instead, this implements what, in the past, we've called a revocable attachment using move. In normal situations the attachment is pinned, as a BAR does not change physical address. However when the VFIO device is closed, or a PCI reset is issued, access to the MMIO memory is revoked.
Revoked means that move occurs, but an attempt to immediately re-map the memory will fail. In the reset case a future move will be triggered when MMIO access returns. As both close and reset are under userspace control it is expected that userspace will suspend use of the dma-buf before doing these operations, the revoke is purely for kernel self-defense against a hostile userspace.
Signed-off-by: Jason Gunthorpe jgg@nvidia.com --- drivers/vfio/pci/Makefile | 1 + drivers/vfio/pci/dma_buf.c | 269 +++++++++++++++++++++++++++++ drivers/vfio/pci/vfio_pci_config.c | 8 +- drivers/vfio/pci/vfio_pci_core.c | 28 ++- drivers/vfio/pci/vfio_pci_priv.h | 23 +++ include/linux/vfio_pci_core.h | 1 + include/uapi/linux/vfio.h | 18 ++ 7 files changed, 340 insertions(+), 8 deletions(-) create mode 100644 drivers/vfio/pci/dma_buf.c
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile index 24c524224da5a3..514c12a81127d6 100644 --- a/drivers/vfio/pci/Makefile +++ b/drivers/vfio/pci/Makefile @@ -2,6 +2,7 @@
vfio-pci-core-y := vfio_pci_core.o vfio_pci_intrs.o vfio_pci_rdwr.o vfio_pci_config.o vfio-pci-core-$(CONFIG_VFIO_PCI_ZDEV_KVM) += vfio_pci_zdev.o +vfio-pci-core-$(CONFIG_DMA_SHARED_BUFFER) += dma_buf.o obj-$(CONFIG_VFIO_PCI_CORE) += vfio-pci-core.o
vfio-pci-y := vfio_pci.o diff --git a/drivers/vfio/pci/dma_buf.c b/drivers/vfio/pci/dma_buf.c new file mode 100644 index 00000000000000..11396aeabff405 --- /dev/null +++ b/drivers/vfio/pci/dma_buf.c @@ -0,0 +1,269 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2022, NVIDIA CORPORATION & AFFILIATES. + */ +#include <linux/dma-buf.h> +#include <linux/pci-p2pdma.h> +#include <linux/dma-resv.h> + +#include "vfio_pci_priv.h" + +MODULE_IMPORT_NS(DMA_BUF); + +struct vfio_pci_dma_buf { + struct dma_buf *dmabuf; + struct vfio_pci_core_device *vdev; + struct list_head dmabufs_elm; + unsigned int index; + unsigned int orig_nents; + size_t offset; + bool revoked; +}; + +static int vfio_pci_dma_buf_attach(struct dma_buf *dmabuf, + struct dma_buf_attachment *attachment) +{ + struct vfio_pci_dma_buf *priv = dmabuf->priv; + int rc; + + rc = pci_p2pdma_distance_many(priv->vdev->pdev, &attachment->dev, 1, + true); + if (rc < 0) + attachment->peer2peer = false; + return 0; +} + +static void vfio_pci_dma_buf_unpin(struct dma_buf_attachment *attachment) +{ +} + +static int vfio_pci_dma_buf_pin(struct dma_buf_attachment *attachment) +{ + /* + * Uses the dynamic interface but must always allow for + * dma_buf_move_notify() to do revoke + */ + return -EINVAL; +} + +static struct sg_table * +vfio_pci_dma_buf_map(struct dma_buf_attachment *attachment, + enum dma_data_direction dir) +{ + size_t sgl_size = dma_get_max_seg_size(attachment->dev); + struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv; + struct scatterlist *sgl; + struct sg_table *sgt; + dma_addr_t dma_addr; + unsigned int nents; + size_t offset; + int ret; + + dma_resv_assert_held(priv->dmabuf->resv); + + if (!attachment->peer2peer) + return ERR_PTR(-EPERM); + + if (priv->revoked) + return ERR_PTR(-ENODEV); + + sgt = kzalloc(sizeof(*sgt), GFP_KERNEL); + if (!sgt) + return ERR_PTR(-ENOMEM); + + nents = DIV_ROUND_UP(priv->dmabuf->size, sgl_size); + ret = sg_alloc_table(sgt, nents, GFP_KERNEL); + if (ret) + goto err_kfree_sgt; + + /* + * Since the memory being mapped is a device memory it could never be in + * CPU caches. + */ + dma_addr = dma_map_resource( + attachment->dev, + pci_resource_start(priv->vdev->pdev, priv->index) + + priv->offset, + priv->dmabuf->size, dir, DMA_ATTR_SKIP_CPU_SYNC); + ret = dma_mapping_error(attachment->dev, dma_addr); + if (ret) + goto err_free_sgt; + + /* + * Break the BAR's physical range up into max sized SGL's according to + * the device's requirement. + */ + sgl = sgt->sgl; + for (offset = 0; offset != priv->dmabuf->size;) { + size_t chunk_size = min(priv->dmabuf->size - offset, sgl_size); + + sg_set_page(sgl, NULL, chunk_size, 0); + sg_dma_address(sgl) = dma_addr + offset; + sg_dma_len(sgl) = chunk_size; + sgl = sg_next(sgl); + offset += chunk_size; + } + + /* + * Because we are not going to include a CPU list we want to have some + * chance that other users will detect this by setting the orig_nents to + * 0 and using only nents (length of DMA list) when going over the sgl + */ + priv->orig_nents = sgt->orig_nents; + sgt->orig_nents = 0; + return sgt; + +err_free_sgt: + sg_free_table(sgt); +err_kfree_sgt: + kfree(sgt); + return ERR_PTR(ret); +} + +static void vfio_pci_dma_buf_unmap(struct dma_buf_attachment *attachment, + struct sg_table *sgt, + enum dma_data_direction dir) +{ + struct vfio_pci_dma_buf *priv = attachment->dmabuf->priv; + + sgt->orig_nents = priv->orig_nents; + dma_unmap_resource(attachment->dev, sg_dma_address(sgt->sgl), + priv->dmabuf->size, dir, DMA_ATTR_SKIP_CPU_SYNC); + sg_free_table(sgt); + kfree(sgt); +} + +static void vfio_pci_dma_buf_release(struct dma_buf *dmabuf) +{ + struct vfio_pci_dma_buf *priv = dmabuf->priv; + + /* + * Either this or vfio_pci_dma_buf_cleanup() will remove from the list. + * The refcount prevents both. + */ + if (priv->vdev) { + down_write(&priv->vdev->memory_lock); + list_del_init(&priv->dmabufs_elm); + up_write(&priv->vdev->memory_lock); + vfio_device_put(&priv->vdev->vdev); + } + kfree(priv); +} + +static const struct dma_buf_ops vfio_pci_dmabuf_ops = { + .attach = vfio_pci_dma_buf_attach, + .map_dma_buf = vfio_pci_dma_buf_map, + .pin = vfio_pci_dma_buf_pin, + .unpin = vfio_pci_dma_buf_unpin, + .release = vfio_pci_dma_buf_release, + .unmap_dma_buf = vfio_pci_dma_buf_unmap, +}; + +int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, + struct vfio_device_feature_dma_buf __user *arg, + size_t argsz) +{ + struct vfio_device_feature_dma_buf get_dma_buf; + DEFINE_DMA_BUF_EXPORT_INFO(exp_info); + struct vfio_pci_dma_buf *priv; + int ret; + + ret = vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_GET, + sizeof(get_dma_buf)); + if (ret != 1) + return ret; + + if (copy_from_user(&get_dma_buf, arg, sizeof(get_dma_buf))) + return -EFAULT; + + /* For PCI the region_index is the BAR number like everything else */ + if (get_dma_buf.region_index >= VFIO_PCI_ROM_REGION_INDEX) + return -EINVAL; + + exp_info.ops = &vfio_pci_dmabuf_ops; + exp_info.size = pci_resource_len(vdev->pdev, get_dma_buf.region_index); + if (!exp_info.size) + return -EINVAL; + if (get_dma_buf.offset || get_dma_buf.length) { + if (get_dma_buf.length > exp_info.size || + get_dma_buf.offset >= exp_info.size || + get_dma_buf.length > exp_info.size - get_dma_buf.offset || + get_dma_buf.offset % PAGE_SIZE || + get_dma_buf.length % PAGE_SIZE) + return -EINVAL; + exp_info.size = get_dma_buf.length; + } + exp_info.flags = get_dma_buf.open_flags; + + priv = kzalloc(sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + INIT_LIST_HEAD(&priv->dmabufs_elm); + priv->offset = get_dma_buf.offset; + priv->index = get_dma_buf.region_index; + + exp_info.priv = priv; + priv->dmabuf = dma_buf_export(&exp_info); + if (IS_ERR(priv->dmabuf)) { + ret = PTR_ERR(priv->dmabuf); + kfree(priv); + return ret; + } + + /* dma_buf_put() now frees priv */ + + down_write(&vdev->memory_lock); + dma_resv_lock(priv->dmabuf->resv, NULL); + priv->revoked = !__vfio_pci_memory_enabled(vdev); + priv->vdev = vdev; + vfio_device_get(&vdev->vdev); + list_add_tail(&priv->dmabufs_elm, &vdev->dmabufs); + dma_resv_unlock(priv->dmabuf->resv); + up_write(&vdev->memory_lock); + + /* + * dma_buf_fd() consumes the reference, when the file closes the dmabuf + * will be released. + */ + return dma_buf_fd(priv->dmabuf, get_dma_buf.open_flags); +} + +void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked) +{ + struct vfio_pci_dma_buf *priv; + struct vfio_pci_dma_buf *tmp; + + lockdep_assert_held_write(&vdev->memory_lock); + + list_for_each_entry_safe(priv, tmp, &vdev->dmabufs, dmabufs_elm) { + if (!dma_buf_try_get(priv->dmabuf)) + continue; + if (priv->revoked != revoked) { + dma_resv_lock(priv->dmabuf->resv, NULL); + priv->revoked = revoked; + dma_buf_move_notify(priv->dmabuf); + dma_resv_unlock(priv->dmabuf->resv); + } + dma_buf_put(priv->dmabuf); + } +} + +void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev) +{ + struct vfio_pci_dma_buf *priv; + struct vfio_pci_dma_buf *tmp; + + down_write(&vdev->memory_lock); + list_for_each_entry_safe(priv, tmp, &vdev->dmabufs, dmabufs_elm) { + if (!dma_buf_try_get(priv->dmabuf)) + continue; + dma_resv_lock(priv->dmabuf->resv, NULL); + list_del_init(&priv->dmabufs_elm); + priv->vdev = NULL; + priv->revoked = true; + dma_buf_move_notify(priv->dmabuf); + dma_resv_unlock(priv->dmabuf->resv); + vfio_device_put(&vdev->vdev); + dma_buf_put(priv->dmabuf); + } + up_write(&vdev->memory_lock); +} diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c index d22921efa25987..f8a9c24d04aeb7 100644 --- a/drivers/vfio/pci/vfio_pci_config.c +++ b/drivers/vfio/pci/vfio_pci_config.c @@ -584,10 +584,12 @@ static int vfio_basic_config_write(struct vfio_pci_core_device *vdev, int pos, virt_mem = !!(le16_to_cpu(*virt_cmd) & PCI_COMMAND_MEMORY); new_mem = !!(new_cmd & PCI_COMMAND_MEMORY);
- if (!new_mem) + if (!new_mem) { vfio_pci_zap_and_down_write_memory_lock(vdev); - else + vfio_pci_dma_buf_move(vdev, true); + } else { down_write(&vdev->memory_lock); + }
/* * If the user is writing mem/io enable (new_mem/io) and we @@ -622,6 +624,8 @@ static int vfio_basic_config_write(struct vfio_pci_core_device *vdev, int pos, *virt_cmd &= cpu_to_le16(~mask); *virt_cmd |= cpu_to_le16(new_cmd & mask);
+ if (__vfio_pci_memory_enabled(vdev)) + vfio_pci_dma_buf_move(vdev, false); up_write(&vdev->memory_lock); }
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 885706944e4d96..7e27bfc60440c2 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -504,6 +504,8 @@ void vfio_pci_core_close_device(struct vfio_device *core_vdev) vfio_spapr_pci_eeh_release(vdev->pdev); vfio_pci_core_disable(vdev);
+ vfio_pci_dma_buf_cleanup(vdev); + mutex_lock(&vdev->igate); if (vdev->err_trigger) { eventfd_ctx_put(vdev->err_trigger); @@ -980,7 +982,10 @@ int vfio_pci_try_reset_function(struct vfio_pci_core_device *vdev) */ vfio_pci_set_power_state(vdev, PCI_D0);
+ vfio_pci_dma_buf_move(vdev, true); ret = pci_try_reset_function(vdev->pdev); + if (__vfio_pci_memory_enabled(vdev)) + vfio_pci_dma_buf_move(vdev, false); up_write(&vdev->memory_lock);
return ret; @@ -1210,11 +1215,10 @@ long vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int cmd, } EXPORT_SYMBOL_GPL(vfio_pci_core_ioctl);
-static int vfio_pci_core_feature_token(struct vfio_device *device, u32 flags, - uuid_t __user *arg, size_t argsz) +static int vfio_pci_core_feature_token(struct vfio_pci_core_device *vdev, + u32 flags, uuid_t __user *arg, + size_t argsz) { - struct vfio_pci_core_device *vdev = - container_of(device, struct vfio_pci_core_device, vdev); uuid_t uuid; int ret;
@@ -1241,9 +1245,14 @@ static int vfio_pci_core_feature_token(struct vfio_device *device, u32 flags, int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags, void __user *arg, size_t argsz) { + struct vfio_pci_core_device *vdev = + container_of(device, struct vfio_pci_core_device, vdev); + switch (flags & VFIO_DEVICE_FEATURE_MASK) { case VFIO_DEVICE_FEATURE_PCI_VF_TOKEN: - return vfio_pci_core_feature_token(device, flags, arg, argsz); + return vfio_pci_core_feature_token(vdev, flags, arg, argsz); + case VFIO_DEVICE_FEATURE_DMA_BUF: + return vfio_pci_core_feature_dma_buf(vdev, flags, arg, argsz); default: return -ENOTTY; } @@ -1881,6 +1890,7 @@ void vfio_pci_core_init_device(struct vfio_pci_core_device *vdev, INIT_LIST_HEAD(&vdev->vma_list); INIT_LIST_HEAD(&vdev->sriov_pfs_item); init_rwsem(&vdev->memory_lock); + INIT_LIST_HEAD(&vdev->dmabufs); } EXPORT_SYMBOL_GPL(vfio_pci_core_init_device);
@@ -2227,11 +2237,17 @@ static int vfio_pci_dev_set_hot_reset(struct vfio_device_set *dev_set, * cause the PCI config space reset without restoring the original * state (saved locally in 'vdev->pm_save'). */ - list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) + list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) { + vfio_pci_dma_buf_move(cur, true); vfio_pci_set_power_state(cur, PCI_D0); + }
ret = pci_reset_bus(pdev);
+ list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) + if (__vfio_pci_memory_enabled(cur)) + vfio_pci_dma_buf_move(cur, false); + err_undo: list_for_each_entry(cur, &dev_set->device_list, vdev.dev_set_list) { if (cur == cur_mem) diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h index 5b1cb9a9838442..c295a1166e7a9c 100644 --- a/drivers/vfio/pci/vfio_pci_priv.h +++ b/drivers/vfio/pci/vfio_pci_priv.h @@ -102,4 +102,27 @@ static inline bool vfio_pci_is_vga(struct pci_dev *pdev) return (pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA; }
+#ifdef CONFIG_DMA_SHARED_BUFFER +int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, + struct vfio_device_feature_dma_buf __user *arg, + size_t argsz); +void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev); +void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, bool revoked); +#else +static int +vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, + struct vfio_device_feature_dma_buf __user *arg, + size_t argsz) +{ + return -ENOTTY; +} +static inline void vfio_pci_dma_buf_cleanup(struct vfio_pci_core_device *vdev) +{ +} +static inline void vfio_pci_dma_buf_move(struct vfio_pci_core_device *vdev, + bool revoked) +{ +} +#endif + #endif diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h index e5cf0d3313a694..fb9769d9e5d149 100644 --- a/include/linux/vfio_pci_core.h +++ b/include/linux/vfio_pci_core.h @@ -93,6 +93,7 @@ struct vfio_pci_core_device { struct mutex vma_lock; struct list_head vma_list; struct rw_semaphore memory_lock; + struct list_head dmabufs; };
/* Will be exported for vfio pci drivers usage */ diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index 733a1cddde30a5..1dcfad6dcb6863 100644 --- a/include/uapi/linux/vfio.h +++ b/include/uapi/linux/vfio.h @@ -986,6 +986,24 @@ enum vfio_device_mig_state { VFIO_DEVICE_STATE_RUNNING_P2P = 5, };
+/** + * Upon VFIO_DEVICE_FEATURE_GET create a dma_buf fd for the + * region selected. + * + * open_flags are the typical flags passed to open(2), eg O_RDWR, O_CLOEXEC, + * etc. offset/length specify a slice of the region to create the dmabuf from. + * If both are 0 then the whole region is used. + * + * Return: The fd number on success, -1 and errno is set on failure. + */ +struct vfio_device_feature_dma_buf { + __u32 region_index; + __u32 open_flags; + __u32 offset; + __u64 length; +}; +#define VFIO_DEVICE_FEATURE_DMA_BUF 3 + /* -------- API for Type1 VFIO IOMMU -------- */
/**