On Tue, 17 Dec 2019 22:40:49 +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
> device is still running, that is, in pre-copy phase while guest driver
> still could access those pages. Host device can write to these pages while
> those were mapped. Such pages should be marked dirty so that after
> migration guest driver should still be able to complete the operation.
>
> 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.
>
> 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, 68 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 215aecb25453..101c2b1e72b4 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -974,7 +974,8 @@ static long 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;
> @@ -1049,6 +1050,15 @@ 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) &&
> + (dma_last != dma))
> + vfio_iova_dirty_bitmap(iommu, dma->iova, dma->size,
> + unmap->bitmap_pgsize, unmap->iova,
> + bitmap);
> + else
> + vfio_remove_unpinned_from_pfn_list(dma, true);
> +
> +
> if (!RB_EMPTY_ROOT(&dma->pfn_list)) {
> struct vfio_iommu_type1_dma_unmap nb_unmap;
>
> @@ -1074,6 +1084,7 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> &nb_unmap);
> goto again;
> }
> +
> unmapped += dma->size;
> vfio_remove_dma(iommu, dma);
> }
> @@ -2404,22 +2415,60 @@ 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;
> + long ret, bsize;
>
> minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size);
>
> - if (copy_from_user(&unmap, (void __user *)arg, minsz))
> + if (copy_from_user(&unmap, (void __user *)arg, sizeof(unmap)))
If we only require minsz, how are we going to copy sizeof(unmap)? This
breaks existing userspace. You'll need to copy the remainder of the
user data after validating that they've provided it.
> 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 = __ffs(unmap.bitmap_pgsize);
> + uint64_t iommu_pgmask =
> + ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> +
> + if (((unmap.bitmap_pgsize - 1) & iommu_pgmask) !=
> + (unmap.bitmap_pgsize - 1))
> + return -EINVAL;
> +
> + bsize = verify_bitmap_size(unmap.size >> pgshift,
> + unmap.bitmap_size);
> + if (bsize < 0)
> + return bsize;
> +
> + bitmap = kmalloc(bsize, GFP_KERNEL);
Same allocation that we cannot do. Thanks,
Alex
> + if (!bitmap)
> + return -ENOMEM;
> +
> + if (copy_from_user(bitmap, (void __user *)unmap.bitmap,
> + bsize)) {
> + ret = -EFAULT;
> + goto unmap_exit;
> + }
> + }
> +
> + ret = vfio_dma_do_unmap(iommu, &unmap, bitmap);
> if (ret)
> - return ret;
> + goto unmap_exit;
>
> - return copy_to_user((void __user *)arg, &unmap, minsz) ?
> + if (unmap.flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) {
> + if (copy_to_user((void __user *)unmap.bitmap, bitmap,
> + bsize)) {
> + ret = -EFAULT;
> + goto unmap_exit;
> + }
> + }
> +
> + ret = copy_to_user((void __user *)arg, &unmap, minsz) ?
> -EFAULT : 0;
> +unmap_exit:
> + kfree(bitmap);
> + return ret;
> } else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
> struct vfio_iommu_type1_dirty_bitmap range;
> uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 8268634e7e08..e8e044c4974d 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -964,12 +964,24 @@ 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 */
> };
>
> #define VFIO_IOMMU_UNMAP_DMA _IO(VFIO_TYPE, VFIO_BASE + 14)
