Re: [PATCH v17 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking.

Alex Williamson
2020-03-30T21:19:23Z

On Mon, 30 Mar 2020 22:20:41 +0530
Kirti Wankhede <kwankhede@nvidia.com> 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.
>
> Fixed below error by changing pgsize type from uint64_t to size_t.
> Reported-by: kbuild test robot <lkp@intel.com>
>
> All errors:
> drivers/vfio/vfio_iommu_type1.c:197: undefined reference to `__udivdi3'
>
> drivers/vfio/vfio_iommu_type1.c:225: undefined reference to `__udivdi3'
>
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
> drivers/vfio/vfio_iommu_type1.c | 266 +++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 260 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 70aeab921d0f..5efebc2b60e1 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -71,6 +71,7 @@ struct vfio_iommu {
> unsigned int dma_avail;
> bool v2;
> bool nesting;
> + bool dirty_page_tracking;
> };
>
> struct vfio_domain {
> @@ -91,6 +92,7 @@ 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 {
> @@ -125,7 +127,21 @@ 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 (uint64_t)(INT_MAX - 1)

This was supposed to be (INT_MAX), not (INT_MAX - 1). Thanks,

Alex

> +#define DIRTY_BITMAP_SIZE_MAX DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX)
> +
> 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
> @@ -175,6 +191,77 @@ 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;
> +
> + if (RB_EMPTY_ROOT(&dma->pfn_list))
> + return;
> +
> + 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
> */
> @@ -567,6 +654,18 @@ 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(vfio_pgsize_bitmap(iommu));
> +
> + /*
> + * Bitmap populated with the smallest supported page
> + * size
> + */
> + bitmap_set(dma->bitmap,
> + (vpfn->iova - dma->iova) >> pgshift, 1);
> + }
> }
>
> ret = i;
> @@ -801,6 +900,7 @@ 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++;
> }
> @@ -831,6 +931,57 @@ 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, size_t pgsize,
> + u64 __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 (copy_to_user((void __user *)bitmap, dma->bitmap, bitmap_size))
> + return -EFAULT;
> +
> + /*
> + * 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, npages);
> + vfio_dma_populate_bitmap(dma, pgsize);
> + return 0;
> +}
> +
> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> +{
> + uint64_t bsize;
> +
> + if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_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)
> {
> @@ -1038,16 +1189,16 @@ 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 */
> if (map->size != size || map->vaddr != vaddr || map->iova != iova)
> return -EINVAL;
>
> - mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> + pgsize = (size_t)1 << __ffs(vfio_pgsize_bitmap(iommu));
>
> - WARN_ON(mask & PAGE_MASK);
> + WARN_ON((pgsize - 1) & PAGE_MASK);
>
> /* READ/WRITE from device perspective */
> if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
> @@ -1055,7 +1206,7 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
> if (map->flags & VFIO_DMA_MAP_FLAG_READ)
> prot |= IOMMU_READ;
>
> - if (!prot || !size || (size | iova | vaddr) & mask)
> + if (!prot || !size || (size | iova | vaddr) & (pgsize - 1))
> return -EINVAL;
>
> /* Don't allow IOVA or virtual address wrap */
> @@ -1130,6 +1281,12 @@ 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;
> @@ -2278,6 +2435,93 @@ 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 = 1 << __ffs(vfio_pgsize_bitmap(iommu));
> +
> + mutex_lock(&iommu->lock);
> + 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 =
> + (size_t)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 smallest supported pgsize */
> + if (range.bitmap.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.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);
> + if (iommu->dirty_page_tracking)
> + ret = vfio_iova_dirty_bitmap(iommu, range.iova,
> + range.size, range.bitmap.pgsize,
> + range.bitmap.data);
> + else
> + ret = -EINVAL;
> + mutex_unlock(&iommu->lock);
> +
> + return ret;
> + }
> }
>
> return -ENOTTY;
> @@ -2345,10 +2589,20 @@ 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(vfio_pgsize_bitmap(iommu));
> + /*
> + * 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)