A new VFIO feature, VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR, is added to set CPU-facing memory type attributes for a DMABUF exported from vfio-pci. These are used for subsequent mmap()s of the buffer.
There are two attributes supported: - The default, VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_NC - VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_WC, which results in WC PTEs for the DMABUF's BAR region. Signed-off-by: Matt Evans <[email protected]> --- drivers/vfio/pci/vfio_pci_core.c | 2 ++ drivers/vfio/pci/vfio_pci_dmabuf.c | 57 +++++++++++++++++++++++++++++- drivers/vfio/pci/vfio_pci_priv.h | 14 ++++++++ include/uapi/linux/vfio.h | 27 ++++++++++++++ 4 files changed, 99 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 064906b25467..dc9c6f479e2c 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -1575,6 +1575,8 @@ int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags, return vfio_pci_core_feature_dma_buf(vdev, flags, arg, argsz); case VFIO_DEVICE_FEATURE_DMA_BUF_REVOKE: return vfio_pci_core_feature_dma_buf_revoke(vdev, flags, arg, argsz); + case VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR: + return vfio_pci_core_feature_dma_buf_memattr(vdev, flags, arg, argsz); default: return -ENOTTY; } diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c index b47411992ab6..58b769e65ab8 100644 --- a/drivers/vfio/pci/vfio_pci_dmabuf.c +++ b/drivers/vfio/pci/vfio_pci_dmabuf.c @@ -51,7 +51,10 @@ static int vfio_pci_dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct * * contained within the DMABUF size before calling this. */ - vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); + if (READ_ONCE(priv->memattr) == VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_WC) + vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot); + else + vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); /* See comments in vfio_pci_core_mmap() re VM_ALLOW_ANY_UNCACHED. */ @@ -468,6 +471,7 @@ int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, priv->vdev = vdev; priv->nr_ranges = get_dma_buf.nr_ranges; priv->size = length; + priv->memattr = VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_NC; ret = vdev->pci_ops->get_dmabuf_phys(vdev, &priv->provider, get_dma_buf.region_index, priv->phys_vec, dma_ranges, @@ -755,6 +759,57 @@ int vfio_pci_core_feature_dma_buf_revoke( } } +out_put_buf: + dma_buf_put(dmabuf); + + return ret; +} + +int vfio_pci_core_feature_dma_buf_memattr( + struct vfio_pci_core_device *vdev, u32 flags, + struct vfio_device_feature_dma_buf_memattr __user *arg, + size_t argsz) +{ + struct vfio_device_feature_dma_buf_memattr db_attr; + struct vfio_pci_dma_buf *priv; + struct dma_buf *dmabuf; + int ret; + + if (!vdev->pci_ops || !vdev->pci_ops->get_dmabuf_phys) + return -EOPNOTSUPP; + + ret = vfio_check_feature(flags, argsz, + VFIO_DEVICE_FEATURE_SET, + sizeof(db_attr)); + if (ret != 1) + return ret; + + if (copy_from_user(&db_attr, arg, sizeof(db_attr))) + return -EFAULT; + + dmabuf = dma_buf_get(db_attr.dmabuf_fd); + if (IS_ERR(dmabuf)) + return PTR_ERR(dmabuf); + + /* Verify DMABUF: see comments in vfio_pci_dma_buf_revoke() */ + priv = dmabuf->priv; + if (dmabuf->ops != &vfio_pci_dmabuf_ops || + READ_ONCE(priv->vdev) != vdev) { + ret = -ENODEV; + goto out_put_buf; + } + + switch (db_attr.memattr) { + case VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_NC: + case VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_WC: + WRITE_ONCE(priv->memattr, db_attr.memattr); + ret = 0; + break; + + default: + ret = -ENOENT; + } + out_put_buf: dma_buf_put(dmabuf); diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h index 3c2f2575b670..3ec8b62194f3 100644 --- a/drivers/vfio/pci/vfio_pci_priv.h +++ b/drivers/vfio/pci/vfio_pci_priv.h @@ -41,6 +41,7 @@ struct vfio_pci_dma_buf { struct kref kref; struct completion comp; unsigned long vma_pgoff_adjust; + u32 memattr; enum vfio_pci_dma_buf_status status; }; @@ -158,6 +159,10 @@ int vfio_pci_core_feature_dma_buf_revoke( struct vfio_pci_core_device *vdev, u32 flags, struct vfio_device_feature_dma_buf_revoke __user *arg, size_t argsz); +int vfio_pci_core_feature_dma_buf_memattr( + struct vfio_pci_core_device *vdev, u32 flags, + struct vfio_device_feature_dma_buf_memattr __user *arg, + size_t argsz); #else static inline int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, @@ -166,6 +171,7 @@ vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags, { return -ENOTTY; } + static inline int vfio_pci_core_feature_dma_buf_revoke( struct vfio_pci_core_device *vdev, u32 flags, struct vfio_device_feature_dma_buf_revoke __user *arg, @@ -173,6 +179,14 @@ static inline int vfio_pci_core_feature_dma_buf_revoke( { return -ENOTTY; } + +static inline int vfio_pci_core_feature_dma_buf_memattr( + struct vfio_pci_core_device *vdev, u32 flags, + struct vfio_device_feature_dma_buf_memattr __user *arg, + size_t argsz) +{ + return -ENOTTY; +} #endif #endif diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h index 697c0bb4b9bc..ab30b89399d0 100644 --- a/include/uapi/linux/vfio.h +++ b/include/uapi/linux/vfio.h @@ -1554,6 +1554,33 @@ struct vfio_device_feature_dma_buf_revoke { __s32 dmabuf_fd; }; +/** + * Given a dma_buf fd previously created by + * VFIO_DEVICE_FEATURE_DMA_BUF, SET the memory attribute that will be + * used by future mmap()s of that fd. SETting a new attribute does + * not affect existing VMAs. + * + * The default, if no previous SET has been performed, is NC. + * + * Return: 0 on success, -1 and errno is set on failure: + * + * EBADF, EINVAL: dmabuf_fd is not a DMABUF fd. + * ENODEV: The dmabuf_fd does not match this VFIO device. + * ENOENT: The given memattr is not supported. + */ +#define VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR 14 + +/* Valid memory attributes for the memattr field */ +enum vfio_device_dma_buf_memattr { + VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_NC = 0, /* pgprot_noncached */ + VFIO_DEVICE_FEATURE_DMA_BUF_MEMATTR_WC = 1, /* pgprot_writecombine */ +}; + +struct vfio_device_feature_dma_buf_memattr { + __s32 dmabuf_fd; + __u32 memattr; +}; + /* -------- API for Type1 VFIO IOMMU -------- */ /** -- 2.50.1 (Apple Git-155)
