Re: [PATCH Kernel v24 5/8] vfio iommu: Implementation of ioctl for dirty pages tracking

[Alex Williamson <alex.williamson@redhat.com>]

On Tue, 2 Jun 2020 21:21:30 +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.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
> 
> Fixed error reported by build bot by changing pgsize type from uint64_t
> to size_t.
> Reported-by: kbuild test robot <lkp@intel.com>
> ---
> 
> Fixed errors and sparse warnings reported by kbuild test robot
> Reported-by: kbuild test robot <lkp@intel.com>
> 
> ld: drivers/vfio/vfio_iommu_type1.o: in function `vfio_dma_populate_bitmap':
> >> vfio_iommu_type1.c:(.text+0x666): undefined reference to `__udivdi3'  

Hi Kirti,

This is already in linux-next, could you please send just the
incremental fix with a Fixes: tag?  Thanks,

Alex

>  drivers/vfio/vfio_iommu_type1.c | 315 +++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 309 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 814c795a2543..8362a36c0de4 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 +191,81 @@ 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;
> +
> +	/*
> +	 * Allocate extra 64 bits that are used to calculate shift required for
> +	 * bitmap_shift_left() to manipulate and club unaligned number of pages
> +	 * in adjacent vfio_dma ranges.
> +	 */
> +	dma->bitmap = kvzalloc(DIRTY_BITMAP_BYTES(npages) + sizeof(u64),
> +			       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;
> +	unsigned long pgshift = __ffs(pgsize);
> +
> +	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) >> pgshift, 1);
> +	}
> +}
> +
> +static int vfio_dma_bitmap_alloc_all(struct vfio_iommu *iommu, size_t pgsize)
> +{
> +	struct rb_node *n;
> +
> +	for (n = rb_first(&iommu->dma_list); 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;
> +
> +			for (p = rb_prev(n); 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;
> +
> +	for (n = rb_first(&iommu->dma_list); 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
>   */
> @@ -598,6 +688,17 @@ 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;
> @@ -832,6 +933,7 @@ 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++;
>  }
> @@ -859,6 +961,94 @@ static void vfio_update_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, nbits);
> +
> +	if (shift) {
> +		bitmap_shift_left(dma->bitmap, dma->bitmap, shift,
> +				  nbits + shift);
> +
> +		if (copy_from_user(&leftover,
> +				   (void __user *)(bitmap + copy_offset),
> +				   sizeof(leftover)))
> +			return -EFAULT;
> +
> +		bitmap_or(dma->bitmap, dma->bitmap, &leftover, shift);
> +	}
> +
> +	if (copy_to_user((void __user *)(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 *dma = rb_entry(n, struct vfio_dma, node);
> +
> +		if (dma->iova < iova)
> +			continue;
> +
> +		if (dma->iova > iova + size - 1)
> +			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);
> +	}
> +	return 0;
> +}
> +
> +static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
> +{
> +	if (!npages || !bitmap_size || (bitmap_size > DIRTY_BITMAP_SIZE_MAX) ||
> +	    (bitmap_size < DIRTY_BITMAP_BYTES(npages)))
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +
>  static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  			     struct vfio_iommu_type1_dma_unmap *unmap)
>  {
> @@ -1076,7 +1266,7 @@ 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 */
> @@ -1091,11 +1281,11 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
>  
>  	mutex_lock(&iommu->lock);
>  
> -	mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1;
> +	pgsize = (size_t)1 << __ffs(iommu->pgsize_bitmap);
>  
> -	WARN_ON(mask & PAGE_MASK);
> +	WARN_ON((pgsize - 1) & PAGE_MASK);
>  
> -	if (!prot || !size || (size | iova | vaddr) & mask) {
> +	if (!prot || !size || (size | iova | vaddr) & (pgsize - 1)) {
>  		ret = -EINVAL;
>  		goto out_unlock;
>  	}
> @@ -1172,6 +1362,12 @@ 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;
> @@ -2318,6 +2514,104 @@ 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;
> +
> +			mutex_lock(&iommu->lock);
> +			pgsize = 1 << __ffs(iommu->pgsize_bitmap);
> +			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;
> +
> +			if (!data_size || data_size < sizeof(range))
> +				return -EINVAL;
> +
> +			if (copy_from_user(&range, (void __user *)(arg + minsz),
> +					   sizeof(range)))
> +				return -EFAULT;
> +
> +			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);
> +
> +			iommu_pgsize = (size_t)1 << __ffs(iommu->pgsize_bitmap);
> +
> +			/* allow only smallest supported pgsize */
> +			if (range.bitmap.pgsize != iommu_pgsize) {
> +				ret = -EINVAL;
> +				goto out_unlock;
> +			}
> +			if (range.iova & (iommu_pgsize - 1)) {
> +				ret = -EINVAL;
> +				goto out_unlock;
> +			}
> +			if (!range.size || range.size & (iommu_pgsize - 1)) {
> +				ret = -EINVAL;
> +				goto out_unlock;
> +			}
> +
> +			if (iommu->dirty_page_tracking)
> +				ret = vfio_iova_dirty_bitmap(range.bitmap.data,
> +						iommu, range.iova, range.size,
> +						range.bitmap.pgsize);
> +			else
> +				ret = -EINVAL;
> +out_unlock:
> +			mutex_unlock(&iommu->lock);
> +
> +			return ret;
> +		}
>  	}
>  
>  	return -ENOTTY;
> @@ -2385,10 +2679,19 @@ 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(iommu->pgsize_bitmap);
> +			/*
> +			 * 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)