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Re: [PATCH Kernel v20 5/8] vfio iommu: Implementation of ioctl for dirty
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From: |
Alex Williamson |
|
Subject: |
Re: [PATCH Kernel v20 5/8] vfio iommu: Implementation of ioctl for dirty pages tracking |
|
Date: |
Thu, 14 May 2020 21:27:20 -0600 |
On Fri, 15 May 2020 02:07:44 +0530
Kirti Wankhede <address@hidden> wrote:
> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
> - Start dirty pages tracking while migration is active
> - Stop dirty pages tracking.
> - Get dirty pages bitmap. Its user space application's responsibility to
> copy content of dirty pages from source to destination during migration.
>
> To prevent DoS attack, memory for bitmap is allocated per vfio_dma
> structure. Bitmap size is calculated considering smallest supported page
> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled
>
> Bitmap is populated for already pinned pages when bitmap is allocated for
> a vfio_dma with the smallest supported page size. Update bitmap from
> pinning functions when tracking is enabled. When user application queries
> bitmap, check if requested page size is same as page size used to
> populated bitmap. If it is equal, copy bitmap, but if not equal, return
> error.
>
> Signed-off-by: Kirti Wankhede <address@hidden>
> Reviewed-by: Neo Jia <address@hidden>
>
> Fixed error reported by build bot by changing pgsize type from uint64_t
> to size_t.
> Reported-by: kbuild test robot <address@hidden>
> ---
> drivers/vfio/vfio_iommu_type1.c | 294
> +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 288 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index de17787ffece..b76d3b14abfd 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -72,6 +72,7 @@ struct vfio_iommu {
> uint64_t pgsize_bitmap;
> bool v2;
> bool nesting;
> + bool dirty_page_tracking;
> };
>
> struct vfio_domain {
> @@ -92,6 +93,7 @@ struct vfio_dma {
> bool lock_cap; /* capable(CAP_IPC_LOCK) */
> struct task_struct *task;
> struct rb_root pfn_list; /* Ex-user pinned pfn list */
> + unsigned long *bitmap;
> };
>
> struct vfio_group {
> @@ -126,6 +128,19 @@ struct vfio_regions {
> #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \
> (!list_empty(&iommu->domain_list))
>
> +#define DIRTY_BITMAP_BYTES(n) (ALIGN(n, BITS_PER_TYPE(u64)) /
> BITS_PER_BYTE)
> +
> +/*
> + * Input argument of number of bits to bitmap_set() is unsigned integer,
> which
> + * further casts to signed integer for unaligned multi-bit operation,
> + * __bitmap_set().
> + * Then maximum bitmap size supported is 2^31 bits divided by 2^3 bits/byte,
> + * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page
> + * system.
> + */
> +#define DIRTY_BITMAP_PAGES_MAX ((u64)INT_MAX)
> +#define DIRTY_BITMAP_SIZE_MAX
> DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
> +
> static int put_pfn(unsigned long pfn, int prot);
>
> /*
> @@ -176,6 +191,74 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu,
> struct vfio_dma *old)
> rb_erase(&old->node, &iommu->dma_list);
> }
>
> +
> +static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, size_t pgsize)
> +{
> + uint64_t npages = dma->size / pgsize;
> +
> + if (npages > DIRTY_BITMAP_PAGES_MAX)
> + return -EINVAL;
> +
> + dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages), GFP_KERNEL);
> + if (!dma->bitmap)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> +static void vfio_dma_bitmap_free(struct vfio_dma *dma)
> +{
> + kfree(dma->bitmap);
> + dma->bitmap = NULL;
> +}
> +
> +static void vfio_dma_populate_bitmap(struct vfio_dma *dma, size_t pgsize)
> +{
> + struct rb_node *p;
> +
> + for (p = rb_first(&dma->pfn_list); p; p = rb_next(p)) {
> + struct vfio_pfn *vpfn = rb_entry(p, struct vfio_pfn, node);
> +
> + bitmap_set(dma->bitmap, (vpfn->iova - dma->iova) / pgsize, 1);
> + }
> +}
> +
> +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, size_t pgsize)
> +{
> + struct rb_node *n = rb_first(&iommu->dma_list);
> +
> + for (; n; n = rb_next(n)) {
> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> + int ret;
> +
> + ret = vfio_dma_bitmap_alloc(dma, pgsize);
> + if (ret) {
> + struct rb_node *p = rb_prev(n);
> +
> + for (; p; p = rb_prev(p)) {
> + struct vfio_dma *dma = rb_entry(n,
> + struct vfio_dma, node);
> +
> + vfio_dma_bitmap_free(dma);
> + }
> + return ret;
> + }
> + vfio_dma_populate_bitmap(dma, pgsize);
> + }
> + return 0;
> +}
> +
> +static void vfio_dma_bitmap_free_all(struct vfio_iommu *iommu)
> +{
> + struct rb_node *n = rb_first(&iommu->dma_list);
> +
> + for (; n; n = rb_next(n)) {
> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> +
> + vfio_dma_bitmap_free(dma);
> + }
> +}
> +
> /*
> * Helper Functions for host iova-pfn list
> */
> @@ -568,6 +651,17 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
> vfio_unpin_page_external(dma, iova, do_accounting);
> goto pin_unwind;
> }
> +
> + if (iommu->dirty_page_tracking) {
> + unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
> +
> + /*
> + * Bitmap populated with the smallest supported page
> + * size
> + */
> + bitmap_set(dma->bitmap,
> + (vpfn->iova - dma->iova) >> pgshift, 1);
> + }
> }
>
> ret = i;
> @@ -802,6 +896,7 @@ static void vfio_remove_dma(struct vfio_iommu *iommu,
> struct vfio_dma *dma)
> vfio_unmap_unpin(iommu, dma, true);
> vfio_unlink_dma(iommu, dma);
> put_task_struct(dma->task);
> + vfio_dma_bitmap_free(dma);
> kfree(dma);
> iommu->dma_avail++;
> }
> @@ -829,6 +924,80 @@ static void vfio_pgsize_bitmap(struct vfio_iommu *iommu)
> }
> }
>
> +static int update_user_bitmap(u64 __user *bitmap, struct vfio_dma *dma,
> + dma_addr_t base_iova, size_t pgsize)
> +{
> + unsigned long pgshift = __ffs(pgsize);
> + unsigned long nbits = dma->size >> pgshift;
> + unsigned long bit_offset = (dma->iova - base_iova) >> pgshift;
> + unsigned long copy_offset = bit_offset / BITS_PER_LONG;
> + unsigned long shift = bit_offset % BITS_PER_LONG;
> + unsigned long leftover;
> +
> + if (shift) {
> + bitmap_shift_left(dma->bitmap, dma->bitmap, shift,
> + nbits + shift);
> +
> + if (copy_from_user(&leftover, (u64 *)bitmap + copy_offset,
> + sizeof(leftover)))
> + return -EFAULT;
> +
> + bitmap_or(dma->bitmap, dma->bitmap, &leftover, shift);
> + }
> +
> + if (copy_to_user((u64 *)bitmap + copy_offset, dma->bitmap,
> + DIRTY_BITMAP_BYTES(nbits + shift)))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +static int vfio_iova_dirty_bitmap(u64 __user *bitmap, struct vfio_iommu
> *iommu,
> + dma_addr_t iova, size_t size, size_t pgsize)
> +{
> + struct vfio_dma *dma;
> + dma_addr_t i = iova, limit = iova + size;
> + unsigned long pgshift = __ffs(pgsize);
> + size_t sz = size;
> + int ret;
> +
> + while ((dma = vfio_find_dma(iommu, i, sz))) {
This would be a lot more efficient if we walked it as:
struct rb_node *n = rb_first(&iommu->dma_list);
for (; n; n = rb_next(n)) {
struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
if (dma->iova < iova)
continue;
if (dma->iova >= iova + size)
break;
ie. there's no need to start from the beginning of the tree on each
iteration. This I would accept as a follow-on internal implementation
improvement. Thanks,
Alex
> +
> + /* mark all pages dirty if all pages are pinned and mapped. */
> + if (dma->iommu_mapped)
> + bitmap_set(dma->bitmap, 0, dma->size >> pgshift);
> +
> + ret = update_user_bitmap(bitmap, dma, iova, pgsize);
> + if (ret)
> + return ret;
> +
> + /*
> + * Re-populate bitmap to include all pinned pages which are
> + * considered as dirty but exclude pages which are unpinned and
> + * pages which are marked dirty by vfio_dma_rw()
> + */
> + bitmap_clear(dma->bitmap, 0, dma->size >> pgshift);
> + vfio_dma_populate_bitmap(dma, pgsize);
> +
> + i = dma->iova + dma->size;
> + if (i >= limit)
> + break;
> +
> + sz = limit - i;
> + }
> +
> + return 0;
> +}
> +
> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> +{
> + if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_MAX) ||
> + (bitmap_size < DIRTY_BITMAP_BYTES(npages)))
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> struct vfio_iommu_type1_dma_unmap *unmap)
> {
> @@ -1046,7 +1215,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> unsigned long vaddr = map->vaddr;
> size_t size = map->size;
> int ret = 0, prot = 0;
> - uint64_t mask;
> + size_t pgsize;
> struct vfio_dma *dma;
>
> /* Verify that none of our __u64 fields overflow */
> @@ -1061,11 +1230,11 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>
> mutex_lock(&iommu->lock);
>
> - mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1;
> + pgsize = (size_t)1 << __ffs(iommu->pgsize_bitmap);
>
> - WARN_ON(mask & PAGE_MASK);
> + WARN_ON((pgsize - 1) & PAGE_MASK);
>
> - if (!prot || !size || (size | iova | vaddr) & mask) {
> + if (!prot || !size || (size | iova | vaddr) & (pgsize - 1)) {
> ret = -EINVAL;
> goto out_unlock;
> }
> @@ -1142,6 +1311,12 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> else
> ret = vfio_pin_map_dma(iommu, dma, size);
>
> + if (!ret && iommu->dirty_page_tracking) {
> + ret = vfio_dma_bitmap_alloc(dma, pgsize);
> + if (ret)
> + vfio_remove_dma(iommu, dma);
> + }
> +
> out_unlock:
> mutex_unlock(&iommu->lock);
> return ret;
> @@ -2288,6 +2463,104 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>
> return copy_to_user((void __user *)arg, &unmap, minsz) ?
> -EFAULT : 0;
> + } else if (cmd == VFIO_IOMMU_DIRTY_PAGES) {
> + struct vfio_iommu_type1_dirty_bitmap dirty;
> + uint32_t mask = VFIO_IOMMU_DIRTY_PAGES_FLAG_START |
> + VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP |
> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP;
> + int ret = 0;
> +
> + if (!iommu->v2)
> + return -EACCES;
> +
> + minsz = offsetofend(struct vfio_iommu_type1_dirty_bitmap,
> + flags);
> +
> + if (copy_from_user(&dirty, (void __user *)arg, minsz))
> + return -EFAULT;
> +
> + if (dirty.argsz < minsz || dirty.flags & ~mask)
> + return -EINVAL;
> +
> + /* only one flag should be set at a time */
> + if (__ffs(dirty.flags) != __fls(dirty.flags))
> + return -EINVAL;
> +
> + if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> + size_t pgsize;
> +
> + mutex_lock(&iommu->lock);
> + pgsize = 1 << __ffs(iommu->pgsize_bitmap);
> + if (!iommu->dirty_page_tracking) {
> + ret = vfio_dma_bitmap_alloc_all(iommu, pgsize);
> + if (!ret)
> + iommu->dirty_page_tracking = true;
> + }
> + mutex_unlock(&iommu->lock);
> + return ret;
> + } else if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
> + mutex_lock(&iommu->lock);
> + if (iommu->dirty_page_tracking) {
> + iommu->dirty_page_tracking = false;
> + vfio_dma_bitmap_free_all(iommu);
> + }
> + mutex_unlock(&iommu->lock);
> + return 0;
> + } else if (dirty.flags &
> + VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
> + struct vfio_iommu_type1_dirty_bitmap_get range;
> + unsigned long pgshift;
> + size_t data_size = dirty.argsz - minsz;
> + size_t iommu_pgsize;
> +
> + if (!data_size || data_size < sizeof(range))
> + return -EINVAL;
> +
> + if (copy_from_user(&range, (void __user *)(arg + minsz),
> + sizeof(range)))
> + return -EFAULT;
> +
> + if (range.iova + range.size < range.iova)
> + return -EINVAL;
> + if (!access_ok((void __user *)range.bitmap.data,
> + range.bitmap.size))
> + return -EINVAL;
> +
> + pgshift = __ffs(range.bitmap.pgsize);
> + ret = verify_bitmap_size(range.size >> pgshift,
> + range.bitmap.size);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&iommu->lock);
> +
> + iommu_pgsize = (size_t)1 << __ffs(iommu->pgsize_bitmap);
> +
> + /* allow only smallest supported pgsize */
> + if (range.bitmap.pgsize != iommu_pgsize) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> + if (range.iova & (iommu_pgsize - 1)) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> + if (!range.size || range.size & (iommu_pgsize - 1)) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + if (iommu->dirty_page_tracking)
> + ret = vfio_iova_dirty_bitmap(range.bitmap.data,
> + iommu, range.iova, range.size,
> + range.bitmap.pgsize);
> + else
> + ret = -EINVAL;
> +out_unlock:
> + mutex_unlock(&iommu->lock);
> +
> + return ret;
> + }
> }
>
> return -ENOTTY;
> @@ -2355,10 +2628,19 @@ static int vfio_iommu_type1_dma_rw_chunk(struct
> vfio_iommu *iommu,
>
> vaddr = dma->vaddr + offset;
>
> - if (write)
> + if (write) {
> *copied = copy_to_user((void __user *)vaddr, data,
> count) ? 0 : count;
> - else
> + if (*copied && iommu->dirty_page_tracking) {
> + unsigned long pgshift = __ffs(iommu->pgsize_bitmap);
> + /*
> + * Bitmap populated with the smallest supported page
> + * size
> + */
> + bitmap_set(dma->bitmap, offset >> pgshift,
> + *copied >> pgshift);
> + }
> + } else
> *copied = copy_from_user(data, (void __user *)vaddr,
> count) ? 0 : count;
> if (kthread)
- [PATCH Kernel v20 0/8] Add UAPIs to support migration for VFIO devices, Kirti Wankhede, 2020/05/14
- [PATCH Kernel v20 1/8] vfio: UAPI for migration interface for device state, Kirti Wankhede, 2020/05/14
- [PATCH Kernel v20 2/8] vfio iommu: Remove atomicity of ref_count of pinned pages, Kirti Wankhede, 2020/05/14
- [PATCH Kernel v20 3/8] vfio iommu: Cache pgsize_bitmap in struct vfio_iommu, Kirti Wankhede, 2020/05/14
- [PATCH Kernel v20 4/8] vfio iommu: Add ioctl definition for dirty pages tracking, Kirti Wankhede, 2020/05/14
- [PATCH Kernel v20 5/8] vfio iommu: Implementation of ioctl for dirty pages tracking, Kirti Wankhede, 2020/05/14
[PATCH Kernel v20 6/8] vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap, Kirti Wankhede, 2020/05/14