Re: [PATCH] vfio/type1: Fix vfio_find_dma_valid return

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

On Thu, 19 Aug 2021 16:53:57 -0700
Anthony Yznaga <anthony.yznaga@oracle.com> wrote:

> Fix vfio_find_dma_valid to return WAITED on success if it was necessary
> to wait which mean iommu lock was dropped and reacquired.  This allows
> vfio_iommu_type1_pin_pages to recheck vaddr_invalid_count and possibly
> avoid the checking the validity of every vaddr in its list.
> 
> Signed-off-by: Anthony Yznaga <anthony.yznaga@oracle.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index a3e925a41b0d..7ca8c4e95da4 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -612,6 +612,7 @@ static int vfio_find_dma_valid(struct vfio_iommu *iommu, dma_addr_t start,
>  			       size_t size, struct vfio_dma **dma_p)
>  {
>  	int ret;
> +	int waited = 0;
>  
>  	do {
>  		*dma_p = vfio_find_dma(iommu, start, size);
> @@ -620,10 +621,10 @@ static int vfio_find_dma_valid(struct vfio_iommu *iommu, dma_addr_t start,
>  		else if (!(*dma_p)->vaddr_invalid)
>  			ret = 0;
>  		else
> -			ret = vfio_wait(iommu);
> +			ret = waited = vfio_wait(iommu);
>  	} while (ret > 0);
>  
> -	return ret;
> +	return ret ? ret : waited;
>  }
>  
>  /*

How about...

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 0b4f7c174c7a..0e9217687f5c 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -612,17 +612,17 @@ static int vfio_wait(struct vfio_iommu *iommu)
 static int vfio_find_dma_valid(struct vfio_iommu *iommu, dma_addr_t start,
 			       size_t size, struct vfio_dma **dma_p)
 {
-	int ret;
+	int ret = 0;
 
 	do {
 		*dma_p = vfio_find_dma(iommu, start, size);
 		if (!*dma_p)
-			ret = -EINVAL;
+			return -EINVAL;
 		else if (!(*dma_p)->vaddr_invalid)
-			ret = 0;
+			return ret;
 		else
 			ret = vfio_wait(iommu);
-	} while (ret > 0);
+	} while (ret == WAITED);
 
 	return ret;
 }