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| From: | Kirti Wankhede |
| Subject: | Re: [PATCH v13 Kernel 5/7] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap |
| Date: | Tue, 17 Mar 2020 23:58:31 +0530 |
| User-agent: | Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 |
On 3/14/2020 12:15 AM, Alex Williamson wrote:
On Thu, 12 Mar 2020 23:23:25 +0530 Kirti Wankhede <address@hidden> 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?
For whatever operation guest driver was using that memory for.
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?
Right.
Signed-off-by: Kirti Wankhede <address@hidden> Reviewed-by: Neo Jia <address@hidden> --- 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.
Removed this with the use of vfio_bitmap structure.
+ 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.
Added.
+ 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.
Updating tests here. Removing redundant tests which are already in vfio_dma_do_unmap()
+ + 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?
Yeah, keeping the original one.
} 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)
Ok. Updating. Thanks, Kirti
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