linux-kernel - Re: [PATCH 4/5] vfio/iommu_type1: Clean up update_dirty_scope in detach

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Message-ID: <YqDgdqVIEwWF1Lku@Asurada-Nvidia>
Date:   Wed, 8 Jun 2022 10:46:30 -0700
From:   Nicolin Chen <nicolinc@...dia.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
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Subject: Re: [PATCH 4/5] vfio/iommu_type1: Clean up update_dirty_scope in
 detach_group()

On Wed, Jun 08, 2022 at 08:35:47AM +0000, Tian, Kevin wrote:

> > @@ -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...

Hmm..you are right. It should be placed outside:
		if (list_empty(&domain->group_list)) {
			...
		}
+		if (!group->pinned_page_dirty_scope) {
+			...
+		}

Will fix this and the same problem in PATCH-5 too.

Thanks!