On Thu, 12 Mar 2020 23:23:25 +0530
Kirti Wankhede <kwankhede@xxxxxxxxxx> wrote:
> Pages, pinned by external interface for requested IO virtual address
> range, might get unpinned and unmapped while migration is active and
"DMA mapped pages, including those pinned by mdev vendor drivers, might
get..."
> device is still running, that is, in pre-copy phase while guest driver
"...running. For example, in pre-copy..."
> still could access those pages. Host device can write to these pages while
> those were mapped.
"...those pages, host device or vendor driver can dirty these mapped
pages."
> Such pages should be marked dirty so that after
> migration guest driver should still be able to complete the operation.
Complete what operation? We need to report these dirty pages in order
to maintain memory consistency for a user making use of dirty page
tracking.
> To get bitmap during unmap, user should set flag
> VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP, bitmap memory should be allocated and
> zeroed by user space application. Bitmap size and page size should be set
> by user application.
It seems like zeroed pages are no longer strictly necessary now that we
require requests to match existing mappings, right?
> Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
> Reviewed-by: Neo Jia <cjia@xxxxxxxxxx>
> ---
> drivers/vfio/vfio_iommu_type1.c | 63 +++++++++++++++++++++++++++++++++++++----
> include/uapi/linux/vfio.h | 12 ++++++++
> 2 files changed, 70 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 435e84269a28..4037b82c6db0 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -976,7 +976,8 @@ static int verify_bitmap_size(unsigned long npages, unsigned long 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,
> + unsigned long *bitmap)
> {
> uint64_t mask;
> struct vfio_dma *dma, *dma_last = NULL;
> @@ -1027,6 +1028,10 @@ 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);
> @@ -1034,6 +1039,13 @@ 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)) {
> + 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;
> @@ -1051,6 +1063,11 @@ 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)
> + vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size,
> + unmap->bitmap_pgsize,
> + (unsigned char __user *) bitmap);
> +
> if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
> struct vfio_iommu_type1_dma_unmap nb_unmap;
>
> @@ -1076,6 +1093,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> &nb_unmap);
> goto again;
> }
> +
> unmapped += dma->size;
> vfio_remove_dma(iommu, dma);
> }
Spurious white space.
> @@ -2406,22 +2424,57 @@ 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;
> + unsigned long *bitmap = NULL;
Shouldn't this have a __user attribute? Also long doesn't seem the
right type. void would be ok here.
> + long ret, bsize;
>
> 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_pgsizes = vfio_pgsize_bitmap(iommu);
> + uint64_t iommu_pgmask =
> + ((uint64_t)1 << __ffs(iommu_pgsizes)) - 1;
> +
Need to test that unmap.argsz includes this.
> + if (copy_from_user(&unmap, (void __user *)arg,
> + sizeof(unmap)))
> + return -EFAULT;
> +
> + pgshift = __ffs(unmap.bitmap_pgsize);
> +
> + if (((unmap.bitmap_pgsize - 1) & iommu_pgmask) !=
> + (unmap.bitmap_pgsize - 1))
> + return -EINVAL;
> +
> + if ((unmap.bitmap_pgsize & iommu_pgsizes) !=
> + unmap.bitmap_pgsize)
> + return -EINVAL;
> + if (unmap.iova + unmap.size < unmap.iova)
> + return -EINVAL;
> + if (!access_ok((void __user *)unmap.bitmap,
> + unmap.bitmap_size))
> + return -EINVAL;
These tests should be identical to the previous patch.
> +
> + bsize = verify_bitmap_size(unmap.size >> pgshift,
> + unmap.bitmap_size);
> + if (bsize < 0)
> + return bsize;
> + bitmap = unmap.bitmap;
> + }
> +
> + ret = vfio_dma_do_unmap(iommu, &unmap, bitmap);
> if (ret)
> return ret;
>
> - return copy_to_user((void __user *)arg, &unmap, minsz) ?
> + ret = copy_to_user((void __user *)arg, &unmap, minsz) ?
> -EFAULT : 0;
> + return ret;
Why? Leftover debugging?
> } else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
> struct vfio_iommu_type1_dirty_bitmap dirty;
> uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 02d555cc7036..12b2094f887e 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -1004,12 +1004,24 @@ struct vfio_iommu_type1_dma_map {
> * 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 should
> + * allocate memory to get bitmap, clear the bitmap memory by setting zero and
> + * should set size of allocated memory in bitmap_size field. One bit in bitmap
> + * represents per page , page of user provided page size in 'bitmap_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 bitmap.
> */
> 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) */
> + __u64 bitmap_pgsize; /* page size for bitmap */
> + __u64 bitmap_size; /* in bytes */
> + void __user *bitmap; /* one bit per page */
This suggests to me that we should further split struct
vfio_iommu_type1_dirty_bitmap_get so that we can use the same
sub-structure here. For example:
struct vfio_bitmap {
__u64 pgsize;
__u64 size;
__u64 __user *data;
};
Note we still have a void* rather than __u64* in original above.
Also, why wouldn't we take the same data[] approach as the previous
patch, defining this as the data when the GET_DIRTY_BITMAP flag is set?
Previous patch would be updated to something like:
struct vfio_iommu_type1_dirty_bitmap_get {
__u64 iova;
__u64 size;
struct vfio_bitmap bitmap;
};
> };
>
> #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)
