On Wed, Mar 25, 2020 at 03:32:37AM +0800, Kirti Wankhede wrote:
> DMA mapped pages, including those pinned by mdev vendor drivers, might
> get unpinned and unmapped while migration is active and device is still
> running. For example, in pre-copy phase while guest driver could access
> those pages, host device or vendor driver can dirty these mapped pages.
> Such pages should be marked dirty so as to maintain memory consistency
> for a user making use of dirty page tracking.
>
> To get bitmap during unmap, user should allocate memory for bitmap, set
> size of allocated memory, set page size to be considered for bitmap and
> set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP.
>
> Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
> Reviewed-by: Neo Jia <cjia@xxxxxxxxxx>
> ---
> drivers/vfio/vfio_iommu_type1.c | 54 ++++++++++++++++++++++++++++++++++++++---
> include/uapi/linux/vfio.h | 10 ++++++++
> 2 files changed, 60 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 27ed069c5053..b98a8d79e13a 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -982,7 +982,8 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> }
>
> static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> - struct vfio_iommu_type1_dma_unmap *unmap)
> + struct vfio_iommu_type1_dma_unmap *unmap,
> + struct vfio_bitmap *bitmap)
> {
> uint64_t mask;
> struct vfio_dma *dma, *dma_last = NULL;
> @@ -1033,6 +1034,10 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> * will be returned if these conditions are not met. The v2 interface
> * will only return success and a size of zero if there were no
> * mappings within the range.
> + *
> + * When VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP flag is set, unmap request
> + * must be for single mapping. Multiple mappings with this flag set is
> + * not supported.
> */
> if (iommu->v2) {
> dma = vfio_find_dma(iommu, unmap->iova, 1);
> @@ -1040,6 +1045,13 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> ret = -EINVAL;
> goto unlock;
> }
> +
> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) &&
> + (dma->iova != unmap->iova || dma->size != unmap->size)) {
potential NULL pointer!
And could you address the comments in v14?
How to handle DSI unmaps in vIOMMU
(https://lore.kernel.org/kvm/20200323011041.GB5456@joy-OptiPlex-7040/)
> + ret = -EINVAL;
> + goto unlock;
> + }
> +
> dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0);
> if (dma && dma->iova + dma->size != unmap->iova + unmap->size) {
> ret = -EINVAL;
> @@ -1057,6 +1069,11 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> if (dma->task->mm != current->mm)
> break;
>
> + if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) &&
> + iommu->dirty_page_tracking)
> + vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size,
> + bitmap->pgsize, bitmap->data);
> +
> if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
> struct vfio_iommu_type1_dma_unmap nb_unmap;
>
> @@ -2418,17 +2435,46 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>
> } else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
> struct vfio_iommu_type1_dma_unmap unmap;
> - long ret;
> + struct vfio_bitmap bitmap = { 0 };
> + int ret;
>
> minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size);
>
> if (copy_from_user(&unmap, (void __user *)arg, minsz))
> return -EFAULT;
>
> - if (unmap.argsz < minsz || unmap.flags)
> + if (unmap.argsz < minsz ||
> + unmap.flags & ~VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP)
> return -EINVAL;
>
> - ret = vfio_dma_do_unmap(iommu, &unmap);
> + if (unmap.flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) {
> + unsigned long pgshift;
> + uint64_t iommu_pgsize =
> + 1 << __ffs(vfio_pgsize_bitmap(iommu));
> +
> + if (unmap.argsz < (minsz + sizeof(bitmap)))
> + return -EINVAL;
> +
> + if (copy_from_user(&bitmap,
> + (void __user *)(arg + minsz),
> + sizeof(bitmap)))
> + return -EFAULT;
> +
> + /* allow only min supported pgsize */
> + if (bitmap.pgsize != iommu_pgsize)
> + return -EINVAL;
> + if (!access_ok((void __user *)bitmap.data, bitmap.size))
> + return -EINVAL;
> +
> + pgshift = __ffs(bitmap.pgsize);
> + ret = verify_bitmap_size(unmap.size >> pgshift,
> + bitmap.size);
> + if (ret)
> + return ret;
> +
> + }
> +
> + ret = vfio_dma_do_unmap(iommu, &unmap, &bitmap);
> if (ret)
> return ret;
>
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 0018721fb744..7c888041136f 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -1011,12 +1011,22 @@ struct vfio_bitmap {
> * field. No guarantee is made to the user that arbitrary unmaps of iova
> * or size different from those used in the original mapping call will
> * succeed.
> + * VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP should be set to get dirty bitmap
> + * before unmapping IO virtual addresses. When this flag is set, user must
> + * provide data[] as structure vfio_bitmap. User must allocate memory to get
> + * bitmap and must set size of allocated memory in vfio_bitmap.size field.
> + * A bit in bitmap represents one page of user provided page size in 'pgsize',
> + * consecutively starting from iova offset. Bit set indicates page at that
> + * offset from iova is dirty. Bitmap of pages in the range of unmapped size is
> + * returned in vfio_bitmap.data
> */
> struct vfio_iommu_type1_dma_unmap {
> __u32 argsz;
> __u32 flags;
> +#define VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP (1 << 0)
> __u64 iova; /* IO virtual address */
> __u64 size; /* Size of mapping (bytes) */
> + __u8 data[];
> };
>
> #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)
> --
> 2.7.0
>
