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From:   Kirti Wankhede <kwankhede@nvidia.com>
To:     <alex.williamson@redhat.com>, <cjia@nvidia.com>
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        Kirti Wankhede <kwankhede@nvidia.com>
Subject: [PATCH v13 Kernel 4/7] vfio iommu: Implementation of ioctl to for dirty pages tracking.
Date:   Thu, 12 Mar 2020 23:23:24 +0530
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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@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
---
 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;
+
+		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