RE: [PATCH 4/5] vfio/iommu_type1: Clean up update_dirty_scope in detach_group()

[Tian, Kevin]

> From: Nicolin Chen
> Sent: Monday, June 6, 2022 2:19 PM
> 
> All devices in emulated_iommu_groups have pinned_page_dirty_scope
> set, so the update_dirty_scope in the first list_for_each_entry
> is always false. Clean it up, and move the "if update_dirty_scope"
> part from the detach_group_done routine to the domain_list part.
> 
> Rename the "detach_group_done" goto label accordingly.
> 
> Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 27 ++++++++++++---------------
>  1 file changed, 12 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c
> b/drivers/vfio/vfio_iommu_type1.c
> index f4e3b423a453..b45b1cc118ef 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -2463,14 +2463,12 @@ static void
> vfio_iommu_type1_detach_group(void *iommu_data,
>  	struct vfio_iommu *iommu = iommu_data;
>  	struct vfio_domain *domain;
>  	struct vfio_iommu_group *group;
> -	bool update_dirty_scope = false;
>  	LIST_HEAD(iova_copy);
> 
>  	mutex_lock(&iommu->lock);
>  	list_for_each_entry(group, &iommu->emulated_iommu_groups,
> next) {
>  		if (group->iommu_group != iommu_group)
>  			continue;
> -		update_dirty_scope = !group->pinned_page_dirty_scope;
>  		list_del(&group->next);
>  		kfree(group);
> 
> @@ -2479,7 +2477,7 @@ static void vfio_iommu_type1_detach_group(void
> *iommu_data,
>  			WARN_ON(iommu->notifier.head);
>  			vfio_iommu_unmap_unpin_all(iommu);
>  		}
> -		goto detach_group_done;
> +		goto out_unlock;
>  	}
> 
>  	/*
> @@ -2495,9 +2493,7 @@ static void vfio_iommu_type1_detach_group(void
> *iommu_data,
>  			continue;
> 
>  		iommu_detach_group(domain->domain, group-
> >iommu_group);
> -		update_dirty_scope = !group->pinned_page_dirty_scope;
>  		list_del(&group->next);
> -		kfree(group);
>  		/*
>  		 * Group ownership provides privilege, if the group list is
>  		 * empty, the domain goes away. If it's the last domain with
> @@ -2519,7 +2515,17 @@ static void vfio_iommu_type1_detach_group(void
> *iommu_data,
>  			kfree(domain);
>  			vfio_iommu_aper_expand(iommu, &iova_copy);
>  			vfio_update_pgsize_bitmap(iommu);
> +			/*
> +			 * Removal of a group without dirty tracking may
> allow
> +			 * the iommu scope to be promoted.
> +			 */
> +			if (!group->pinned_page_dirty_scope) {
> +				iommu->num_non_pinned_groups--;
> +				if (iommu->dirty_page_tracking)
> +
> 	vfio_iommu_populate_bitmap_full(iommu);

This doesn't look correct. The old code decrements
num_non_pinned_groups for every detach group without dirty
tracking. But now it's only done when the domain is about to
be released...

> +			}
>  		}
> +		kfree(group);
>  		break;
>  	}
> 
> @@ -2528,16 +2534,7 @@ static void vfio_iommu_type1_detach_group(void
> *iommu_data,
>  	else
>  		vfio_iommu_iova_free(&iova_copy);
> 
> -detach_group_done:
> -	/*
> -	 * Removal of a group without dirty tracking may allow the iommu
> scope
> -	 * to be promoted.
> -	 */
> -	if (update_dirty_scope) {
> -		iommu->num_non_pinned_groups--;
> -		if (iommu->dirty_page_tracking)
> -			vfio_iommu_populate_bitmap_full(iommu);
> -	}
> +out_unlock:
>  	mutex_unlock(&iommu->lock);
>  }
> 
> --
> 2.17.1
> 
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