* Kirti Wankhede (kwankhede@xxxxxxxxxx) wrote:
> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
> - Start pinned and unpinned pages tracking while migration is active
> - Stop pinned and unpinned dirty pages tracking. This is also used to
> stop dirty pages tracking if migration failed or cancelled.
> - Get dirty pages bitmap. This ioctl returns bitmap of dirty pages, its
> user space application 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 when dirty logging is enabled for those
> vfio_dmas whose vpfn list is not empty or whole range is mapped, in
> case of pass-through device.
>
> 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 and unpinning functions. 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 <kwankhede@xxxxxxxxxx>
> Reviewed-by: Neo Jia <cjia@xxxxxxxxxx>
> ---
> drivers/vfio/vfio_iommu_type1.c | 243 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 237 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index d386461e5d11..435e84269a28 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -70,6 +70,7 @@ struct vfio_iommu {
> unsigned int dma_avail;
> bool v2;
> bool nesting;
> + bool dirty_page_tracking;
> };
>
> struct vfio_domain {
> @@ -90,6 +91,7 @@ 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 {
> @@ -125,6 +127,7 @@ struct vfio_regions {
> (!list_empty(&iommu->domain_list))
>
> static int put_pfn(unsigned long pfn, int prot);
> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu);
>
> /*
> * This code handles mapping and unmapping of user data buffers
> @@ -174,6 +177,76 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
> rb_erase(&old->node, &iommu->dma_list);
> }
>
> +static inline unsigned long dirty_bitmap_bytes(unsigned int npages)
> +{
> + if (!npages)
> + return 0;
> +
> + return ALIGN(npages, BITS_PER_LONG) / sizeof(unsigned long);
> +}
> +
> +static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, unsigned long pgsize)
> +{
> + if (!RB_EMPTY_ROOT(&dma->pfn_list) || dma->iommu_mapped) {
> + unsigned long npages = dma->size / pgsize;
> +
> + dma->bitmap = kvzalloc(dirty_bitmap_bytes(npages), GFP_KERNEL);
> + if (!dma->bitmap)
> + return -ENOMEM;
> + }
> + return 0;
> +}
> +
> +static int vfio_dma_all_bitmap_alloc(struct vfio_iommu *iommu,
> + unsigned long pgsize)
> +{
> + struct rb_node *n = rb_first(&iommu->dma_list);
> + int ret;
> +
> + for (; n; n = rb_next(n)) {
> + struct vfio_dma *dma = rb_entry(n, struct vfio_dma, node);
> + struct rb_node *n;
> +
> + 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);
> +
> + kfree(dma->bitmap);
> + dma->bitmap = NULL;
> + }
> + return ret;
> + }
> +
> + if (!dma->bitmap)
> + continue;
> +
> + for (n = rb_first(&dma->pfn_list); n; n = rb_next(n)) {
> + struct vfio_pfn *vpfn = rb_entry(n, struct vfio_pfn,
> + node);
> +
> + bitmap_set(dma->bitmap,
> + (vpfn->iova - dma->iova) / pgsize, 1);
> + }
> + }
> + return 0;
> +}
> +
> +static void vfio_dma_all_bitmap_free(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);
> +
> + kfree(dma->bitmap);
> + dma->bitmap = NULL;
> + }
> +}
> +
> /*
> * Helper Functions for host iova-pfn list
> */
> @@ -254,12 +327,16 @@ static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
> return vpfn;
> }
>
> -static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn)
> +static int vfio_iova_put_vfio_pfn(struct vfio_dma *dma, struct vfio_pfn *vpfn,
> + bool do_tracking, unsigned long pgsize)
> {
> int ret = 0;
>
> vpfn->ref_count--;
> if (!vpfn->ref_count) {
> + if (do_tracking && dma->bitmap)
> + bitmap_set(dma->bitmap,
> + (vpfn->iova - dma->iova) / pgsize, 1);
> ret = put_pfn(vpfn->pfn, dma->prot);
> vfio_remove_from_pfn_list(dma, vpfn);
> }
> @@ -484,7 +561,8 @@ static int vfio_pin_page_external(struct vfio_dma *dma, unsigned long vaddr,
> }
>
> static int vfio_unpin_page_external(struct vfio_dma *dma, dma_addr_t iova,
> - bool do_accounting)
> + bool do_accounting, bool do_tracking,
> + unsigned long pgsize)
> {
> int unlocked;
> struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
> @@ -492,7 +570,7 @@ static int vfio_unpin_page_external(struct vfio_dma *dma, dma_addr_t iova,
> if (!vpfn)
> return 0;
>
> - unlocked = vfio_iova_put_vfio_pfn(dma, vpfn);
> + unlocked = vfio_iova_put_vfio_pfn(dma, vpfn, do_tracking, pgsize);
>
> if (do_accounting)
> vfio_lock_acct(dma, -unlocked, true);
> @@ -563,9 +641,26 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>
> ret = vfio_add_to_pfn_list(dma, iova, phys_pfn[i]);
> if (ret) {
> - vfio_unpin_page_external(dma, iova, do_accounting);
> + vfio_unpin_page_external(dma, iova, do_accounting,
> + false, 0);
> goto pin_unwind;
> }
> +
> + if (iommu->dirty_page_tracking) {
> + unsigned long pgshift =
> + __ffs(vfio_pgsize_bitmap(iommu));
> +
> + if (!dma->bitmap) {
> + ret = vfio_dma_bitmap_alloc(dma, 1 << pgshift);
> + if (ret) {
> + vfio_unpin_page_external(dma, iova,
> + do_accounting, false, 0);
> + goto pin_unwind;
> + }
> + }
> + bitmap_set(dma->bitmap,
> + (vpfn->iova - dma->iova) >> pgshift, 1);
> + }
> }
>
> ret = i;
> @@ -578,7 +673,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data,
>
> iova = user_pfn[j] << PAGE_SHIFT;
> dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
> - vfio_unpin_page_external(dma, iova, do_accounting);
> + vfio_unpin_page_external(dma, iova, do_accounting, false, 0);
> phys_pfn[j] = 0;
> }
> pin_done:
> @@ -612,7 +707,8 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data,
> dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
> if (!dma)
> goto unpin_exit;
> - vfio_unpin_page_external(dma, iova, do_accounting);
> + vfio_unpin_page_external(dma, iova, do_accounting,
> + iommu->dirty_page_tracking, PAGE_SIZE);
> }
>
> unpin_exit:
> @@ -800,6 +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);
> + kfree(dma->bitmap);
> kfree(dma);
> iommu->dma_avail++;
> }
> @@ -830,6 +927,54 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
> return bitmap;
> }
>
> +static int vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> + size_t size, uint64_t pgsize,
> + unsigned char __user *bitmap)
> +{
> + struct vfio_dma *dma;
> + unsigned long pgshift = __ffs(pgsize);
> + unsigned int npages, bitmap_size;
> +
> + dma = vfio_find_dma(iommu, iova, 1);
> +
> + if (!dma)
> + return -EINVAL;
> +
> + if (dma->iova != iova || dma->size != size)
> + return -EINVAL;
> +
> + npages = dma->size >> pgshift;
> + bitmap_size = dirty_bitmap_bytes(npages);
> +
> + /* mark all pages dirty if all pages are pinned and mapped. */
> + if (dma->iommu_mapped)
> + bitmap_set(dma->bitmap, 0, npages);
> +
> + if (dma->bitmap) {
> + if (copy_to_user((void __user *)bitmap, dma->bitmap,
> + bitmap_size))
> + return -EFAULT;
> +
> + memset(dma->bitmap, 0, bitmap_size);
> + }
> + return 0;
> +}
> +
> +static int verify_bitmap_size(unsigned long npages, unsigned long bitmap_size)
> +{
> + long bsize;
> +
> + if (!bitmap_size || bitmap_size > SIZE_MAX)
> + return -EINVAL;
> +
> + bsize = dirty_bitmap_bytes(npages);
> +
> + if (bitmap_size < bsize)
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
> struct vfio_iommu_type1_dma_unmap *unmap)
> {
> @@ -2277,6 +2422,92 @@ 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;
> +
> + 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;
It seems a bit odd to use a set of ORable flags when only one can be set
at a time.
> + if (dirty.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> + unsigned long iommu_pgsize =
> + 1 << __ffs(vfio_pgsize_bitmap(iommu));
> +
> + mutex_lock(&iommu->lock);
> + ret = vfio_dma_all_bitmap_alloc(iommu, 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_all_bitmap_free(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;
> + uint64_t iommu_pgsize =
> + 1 << __ffs(vfio_pgsize_bitmap(iommu));
> +
> + if (!data_size || data_size < sizeof(range))
> + return -EINVAL;
> +
> + if (copy_from_user(&range, (void __user *)(arg + minsz),
> + sizeof(range)))
> + return -EFAULT;
> +
> + // allow only min supported pgsize
> + if (range.pgsize != iommu_pgsize)
> + return -EINVAL;
> + if (range.iova & (iommu_pgsize - 1))
> + return -EINVAL;
> + if (!range.size || range.size & (iommu_pgsize - 1))
> + return -EINVAL;
> + if (range.iova + range.size < range.iova)
> + return -EINVAL;
> + if (!access_ok((void __user *)range.bitmap,
> + range.bitmap_size))
> + return -EINVAL;
> +
> + pgshift = __ffs(range.pgsize);
> + ret = verify_bitmap_size(range.size >> pgshift,
> + range.bitmap_size);
> + if (ret)
> + return ret;
> +
> + mutex_lock(&iommu->lock);
> + if (iommu->dirty_page_tracking)
> + ret = vfio_iova_dirty_bitmap(iommu, range.iova,
> + range.size, range.pgsize,
> + (unsigned char __user *)range.bitmap);
> + else
> + ret = -EINVAL;
> + mutex_unlock(&iommu->lock);
> +
> + return ret;
> + }
> }
>
> return -ENOTTY;
> --
> 2.7.0
>
--
Dr. David Alan Gilbert / dgilbert@xxxxxxxxxx / Manchester, UK
