Re: [PATCH v10 Kernel 4/5] vfio iommu: Implementation of ioctl to for dirty pages tracking.

[Yan Zhao <yan.y.zhao@intel.com>]

On Tue, Dec 17, 2019 at 04:21:39AM +0800, Kirti Wankhede wrote:
> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations:
> - Start unpinned pages dirty pages tracking while migration is active and
>   device is running, i.e. during pre-copy phase.
> - Stop unpinned pages dirty pages tracking. This is required to stop
>   unpinned dirty pages tracking if migration failed or cancelled during
>   pre-copy phase. Unpinned pages tracking is clear.
> - Get dirty pages bitmap. Stop unpinned dirty pages tracking and clear
>   unpinned pages information on bitmap read. This ioctl returns bitmap of
>   dirty pages, its user space application responsibility to copy content
>   of dirty pages from source to destination during migration.
> 
> Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Neo Jia <cjia@nvidia.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 210 ++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 203 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 3f6b04f2334f..264449654d3f 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 {
> @@ -112,6 +113,7 @@ struct vfio_pfn {
>  	dma_addr_t		iova;		/* Device address */
>  	unsigned long		pfn;		/* Host pfn */
>  	atomic_t		ref_count;
> +	bool			unpinned;
>  };
>  
>  struct vfio_regions {
> @@ -244,6 +246,32 @@ static void vfio_remove_from_pfn_list(struct vfio_dma *dma,
>  	kfree(vpfn);
>  }
>  
> +static void vfio_remove_unpinned_from_pfn_list(struct vfio_dma *dma, bool warn)
> +{
> +	struct rb_node *n = rb_first(&dma->pfn_list);
> +
> +	for (; n; n = rb_next(n)) {
> +		struct vfio_pfn *vpfn = rb_entry(n, struct vfio_pfn, node);
> +
> +		if (warn)
> +			WARN_ON_ONCE(vpfn->unpinned);
> +
> +		if (vpfn->unpinned)
> +			vfio_remove_from_pfn_list(dma, vpfn);
> +	}
> +}
> +
> +static void vfio_remove_unpinned_from_dma_list(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_remove_unpinned_from_pfn_list(dma, false);
> +	}
> +}
> +
>  static struct vfio_pfn *vfio_iova_get_vfio_pfn(struct vfio_dma *dma,
>  					       unsigned long iova)
>  {
> @@ -254,13 +282,17 @@ 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 dirty_tracking)
>  {
>  	int ret = 0;
>  
>  	if (atomic_dec_and_test(&vpfn->ref_count)) {
>  		ret = put_pfn(vpfn->pfn, dma->prot);
if physical page here is put, it may cause problem when pin this iova
next time:
vfio_iommu_type1_pin_pages {
    ...
    vpfn = vfio_iova_get_vfio_pfn(dma, iova);
    if (vpfn) {
        phys_pfn[i] = vpfn->pfn;
        continue;
    }
    ...
}

> -		vfio_remove_from_pfn_list(dma, vpfn);
> +		if (dirty_tracking)
> +			vpfn->unpinned = true;
> +		else
> +			vfio_remove_from_pfn_list(dma, vpfn);
so the unpinned pages before dirty page tracking is not treated as
dirty?

>  	}
>  	return ret;
>  }
> @@ -504,7 +536,7 @@ 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 dirty_tracking)
>  {
>  	int unlocked;
>  	struct vfio_pfn *vpfn = vfio_find_vpfn(dma, iova);
> @@ -512,7 +544,10 @@ 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);
> +	if (vpfn->unpinned)
> +		return 0;
> +
> +	unlocked = vfio_iova_put_vfio_pfn(dma, vpfn, dirty_tracking);
>  
>  	if (do_accounting)
>  		vfio_lock_acct(dma, -unlocked, true);
> @@ -583,7 +618,8 @@ 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);
>  			goto pin_unwind;
>  		}
>  	}
> @@ -598,7 +634,7 @@ 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);
>  		phys_pfn[j] = 0;
>  	}
>  pin_done:
> @@ -632,7 +668,8 @@ 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);
>  	}
>  
>  unpin_exit:
> @@ -850,6 +887,88 @@ static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
>  	return bitmap;
>  }
>  
> +/*
> + * start_iova is the reference from where bitmaping started. This is called
> + * from DMA_UNMAP where start_iova can be different than iova
> + */
> +
> +static void vfio_iova_dirty_bitmap(struct vfio_iommu *iommu, dma_addr_t iova,
> +				  size_t size, uint64_t pgsize,
> +				  dma_addr_t start_iova, unsigned long *bitmap)
> +{
> +	struct vfio_dma *dma;
> +	dma_addr_t i = iova;
> +	unsigned long pgshift = __ffs(pgsize);
> +
> +	while ((dma = vfio_find_dma(iommu, i, pgsize))) {
> +		/* mark all pages dirty if all pages are pinned and mapped. */
> +		if (dma->iommu_mapped) {
This prevents pass-through devices from calling vfio_pin_pages to do
fine grained log dirty.
> +			dma_addr_t iova_limit;
> +
> +			iova_limit = (dma->iova + dma->size) < (iova + size) ?
> +				     (dma->iova + dma->size) : (iova + size);
> +
> +			for (; i < iova_limit; i += pgsize) {
> +				unsigned int start;
> +
> +				start = (i - start_iova) >> pgshift;
> +
> +				__bitmap_set(bitmap, start, 1);
> +			}
> +			if (i >= iova + size)
> +				return;
> +		} else {
> +			struct rb_node *n = rb_first(&dma->pfn_list);
> +			bool found = false;
> +
> +			for (; n; n = rb_next(n)) {
> +				struct vfio_pfn *vpfn = rb_entry(n,
> +							struct vfio_pfn, node);
> +				if (vpfn->iova >= i) {
> +					found = true;
> +					break;
> +				}
> +			}
> +
> +			if (!found) {
> +				i += dma->size;
> +				continue;
> +			}
> +
> +			for (; n; n = rb_next(n)) {
> +				unsigned int start;
> +				struct vfio_pfn *vpfn = rb_entry(n,
> +							struct vfio_pfn, node);
> +
> +				if (vpfn->iova >= iova + size)
> +					return;
> +
> +				start = (vpfn->iova - start_iova) >> pgshift;
> +
> +				__bitmap_set(bitmap, start, 1);
> +
> +				i = vpfn->iova + pgsize;
> +			}
> +		}
> +		vfio_remove_unpinned_from_pfn_list(dma, false);
> +	}
> +}
> +
> +static long verify_bitmap_size(unsigned long npages, unsigned long bitmap_size)
> +{
> +	long bsize;
> +
> +	if (!bitmap_size || bitmap_size > SIZE_MAX)
> +		return -EINVAL;
> +
> +	bsize = ALIGN(npages, BITS_PER_LONG) / sizeof(unsigned long);
> +
> +	if (bitmap_size < bsize)
> +		return -EINVAL;
> +
> +	return bsize;
> +}
> +
>  static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
>  			     struct vfio_iommu_type1_dma_unmap *unmap)
>  {
> @@ -2298,6 +2417,83 @@ 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 range;
> +		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,
> +				    bitmap);
> +
> +		if (copy_from_user(&range, (void __user *)arg, minsz))
> +			return -EFAULT;
> +
> +		if (range.argsz < minsz || range.flags & ~mask)
> +			return -EINVAL;
> +
> +		if (range.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_START) {
> +			iommu->dirty_page_tracking = true;
> +			return 0;
> +		} else if (range.flags & VFIO_IOMMU_DIRTY_PAGES_FLAG_STOP) {
> +			iommu->dirty_page_tracking = false;
> +
> +			mutex_lock(&iommu->lock);
> +			vfio_remove_unpinned_from_dma_list(iommu);
> +			mutex_unlock(&iommu->lock);
> +			return 0;
> +
> +		} else if (range.flags &
> +				 VFIO_IOMMU_DIRTY_PAGES_FLAG_GET_BITMAP) {
> +			uint64_t iommu_pgmask;
> +			unsigned long pgshift = __ffs(range.pgsize);
> +			unsigned long *bitmap;
> +			long bsize;
> +
> +			iommu_pgmask =
> +			 ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1;
> +
> +			if (((range.pgsize - 1) & iommu_pgmask) !=
> +			    (range.pgsize - 1))
> +				return -EINVAL;
> +
> +			if (range.iova & iommu_pgmask)
> +				return -EINVAL;
> +			if (!range.size || range.size > SIZE_MAX)
> +				return -EINVAL;
> +			if (range.iova + range.size < range.iova)
> +				return -EINVAL;
> +
> +			bsize = verify_bitmap_size(range.size >> pgshift,
> +						   range.bitmap_size);
> +			if (bsize)
> +				return ret;
> +
> +			bitmap = kmalloc(bsize, GFP_KERNEL);
> +			if (!bitmap)
> +				return -ENOMEM;
> +
> +			ret = copy_from_user(bitmap,
> +			     (void __user *)range.bitmap, bsize) ? -EFAULT : 0;
> +			if (ret)
> +				goto bitmap_exit;
> +
> +			iommu->dirty_page_tracking = false;
why iommu->dirty_page_tracking is false here?
suppose this ioctl can be called several times.

Thanks
Yan
> +			mutex_lock(&iommu->lock);
> +			vfio_iova_dirty_bitmap(iommu, range.iova, range.size,
> +					     range.pgsize, range.iova, bitmap);
> +			mutex_unlock(&iommu->lock);
> +
> +			ret = copy_to_user((void __user *)range.bitmap, bitmap,
> +					   range.bitmap_size) ? -EFAULT : 0;
> +bitmap_exit:
> +			kfree(bitmap);
> +			return ret;
> +		}
>  	}
>  
>  	return -ENOTTY;
> -- 
> 2.7.0
>