On Wed, Mar 25, 2020 at 05:18:52AM +0800, Kirti Wankhede 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 <kwankhede@xxxxxxxxxx>
> Reviewed-by: Neo Jia <cjia@xxxxxxxxxx>
> ---
> 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..874a1a7ae925 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)
> +#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, uint64_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, uint64_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, uint64_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, uint64_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;
> +
Still don't sure if it's a good practice.
I saw the qemu implementation.
Qemu just iterates the whole IOVA address space,
It needs to find IOTLB entry for an IOVA
(1) if it can find an IOTLB for an IOVA, do the DIRTY_PAGES IOCTL and
increment IOVA by (iotlb.addr_mask + 1)
(2) if no existing IOTLB found, the imrc->translate needs to go searching shadow
page table to try to generate one.
if it still fails,(most probably case, as IOMMU only maps a small part in its address
space). increment IOVA by 1 page.
So, if the address space width is 39bit, and if there's only one page
mapped, you still have to translate IOVA for around 2^27 times in each
query. Isn't it too inefficient?
So, IMHO, why we could not just save an rb tree specific for dirty pages, then generate
a bitmap for each query?
> + 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);
will this also repopulate bitmap for pinned pages set by pass-through devices in
patch 07 ?
> + 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;
> + uint64_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 = (uint64_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) {
> + uint64_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;
> + 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 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)
> --
> 2.7.0
>
