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

Tian, Kevin
2022-06-08T09:19:39Z

> 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@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
> 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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