On Mon, 18 May 2020 11:26:34 +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 | 313 +++++++++++++++++++++++++++++++++++++++-
1 file changed, 307 insertions(+), 6 deletions(-)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index de17787ffece..bf740fef196f 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);
Curious that the extra 8-bytes are added in the next patch, but they're
just as necessary here.
+ 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)) {
Nit, the previous function above sets the initial value in the for()
statement, it looks like it would fit in 80 columns here too. We have
examples either way in the code, so not a must fix.
+ 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)) {
Same.
+ 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)) {
And another.
+ 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,
+ (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 +924,99 @@ 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;
+
+ /* mark all pages dirty if all pages are pinned and mapped. */
+ if (dma->iommu_mapped)
+ bitmap_set(dma->bitmap, 0, dma->size >> pgshift);
We already calculated 'dma->size >> pgshift' as nbits above, we should
use nbits here. I imagine the compiler will optimize this, so take it
as a nit.
+
+ 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;
+ struct rb_node *n;
+ unsigned long pgshift = __ffs(pgsize);
+ int ret;
+
+ /*
+ * GET_BITMAP request must fully cover vfio_dma mappings. Multiple
+ * vfio_dma mappings may be clubbed by specifying large ranges, but
+ * there must not be any previous mappings bisected by the range.
+ * An error will be returned if these conditions are not met.
+ */
+ dma = vfio_find_dma(iommu, iova, 1);
+ if (dma && dma->iova != iova)
+ return -EINVAL;
+
+ dma = vfio_find_dma(iommu, iova + size - 1, 0);
+ if (dma && dma->iova + dma->size != iova + size)
+ return -EINVAL;
+
+ for (n = rb_first(&iommu->dma_list); n; n = rb_next(n)) {
+ struct vfio_dma *ldma = rb_entry(n, struct vfio_dma, node);
+
+ if (ldma->iova >= iova)
+ break;
+ }
+
+ dma = n ? rb_entry(n, struct vfio_dma, node) : NULL;
+
+ while (dma && (dma->iova >= iova) &&
'dma->iova >= iova' is necessarily true per the above loop, right?
We'd have NULL if we never reach an iova within range.
+ (dma->iova + dma->size <= iova + size)) {
I think 'dma->iova < iova + size' is sufficient here, we've already
tested that there are no dmas overlapping the ends, they're all either
fully contained or fully outside.
+
The double loop here is a little unnecessary, we could combine them
into:
for (n = rb_first(&iommu->dma_list); 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;
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 think what you have works, but it's a little more complicated than it
needs to be. Thanks,