On Fri, 22 Jan 2021 17:26:35 +0800
Keqian Zhu <zhukeqi...@huawei.com> wrote:

> vfio_sanity_check_pfn_list() is used to check whether pfn_list and
> notifier are empty when remove the external domain, so it makes a
> wrong assumption that only external domain will use the pinning
> interface.
> 
> Now we apply the pfn_list check when a vfio_dma is removed and apply
> the notifier check when all domains are removed.
> 
> Fixes: a54eb55045ae ("vfio iommu type1: Add support for mediated devices")
> Signed-off-by: Keqian Zhu <zhukeqi...@huawei.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 33 ++++++++++-----------------------
>  1 file changed, 10 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 161725395f2f..d8c10f508321 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -957,6 +957,7 @@ static long vfio_unmap_unpin(struct vfio_iommu *iommu, 
> struct vfio_dma *dma,
>  
>  static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
>  {
> +     WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list));
>       vfio_unmap_unpin(iommu, dma, true);
>       vfio_unlink_dma(iommu, dma);
>       put_task_struct(dma->task);
> @@ -2250,23 +2251,6 @@ static void vfio_iommu_unmap_unpin_reaccount(struct 
> vfio_iommu *iommu)
>       }
>  }
>  
> -static void vfio_sanity_check_pfn_list(struct vfio_iommu *iommu)
> -{
> -     struct rb_node *n;
> -
> -     n = rb_first(&iommu->dma_list);
> -     for (; n; n = rb_next(n)) {
> -             struct vfio_dma *dma;
> -
> -             dma = rb_entry(n, struct vfio_dma, node);
> -
> -             if (WARN_ON(!RB_EMPTY_ROOT(&dma->pfn_list)))
> -                     break;
> -     }
> -     /* mdev vendor driver must unregister notifier */
> -     WARN_ON(iommu->notifier.head);
> -}
> -
>  /*
>   * Called when a domain is removed in detach. It is possible that
>   * the removed domain decided the iova aperture window. Modify the
> @@ -2366,10 +2350,10 @@ static void vfio_iommu_type1_detach_group(void 
> *iommu_data,
>                       kfree(group);
>  
>                       if (list_empty(&iommu->external_domain->group_list)) {
> -                             vfio_sanity_check_pfn_list(iommu);
> -
> -                             if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu))
> +                             if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)) {
> +                                     WARN_ON(iommu->notifier.head);
>                                       vfio_iommu_unmap_unpin_all(iommu);
> +                             }
>  
>                               kfree(iommu->external_domain);
>                               iommu->external_domain = NULL;
> @@ -2403,10 +2387,12 @@ static void vfio_iommu_type1_detach_group(void 
> *iommu_data,
>                */
>               if (list_empty(&domain->group_list)) {
>                       if (list_is_singular(&iommu->domain_list)) {
> -                             if (!iommu->external_domain)
> +                             if (!iommu->external_domain) {
> +                                     WARN_ON(iommu->notifier.head);
>                                       vfio_iommu_unmap_unpin_all(iommu);
> -                             else
> +                             } else {
>                                       vfio_iommu_unmap_unpin_reaccount(iommu);
> +                             }
>                       }
>                       iommu_domain_free(domain->domain);
>                       list_del(&domain->next);
> @@ -2488,9 +2474,10 @@ static void vfio_iommu_type1_release(void *iommu_data)
>       struct vfio_iommu *iommu = iommu_data;
>       struct vfio_domain *domain, *domain_tmp;
>  
> +     WARN_ON(iommu->notifier.head);

I don't see that this does any harm, but isn't it actually redundant?
It seems vfio-core only calls the iommu backend release function after
removing all the groups, so the tests in _detach_group should catch all
cases.  We're expecting the vfio bus/mdev driver to remove the notifier
when a device is closed, which necessarily occurs before detaching the
group.  Thanks,

Alex

> +
>       if (iommu->external_domain) {
>               vfio_release_domain(iommu->external_domain, true);
> -             vfio_sanity_check_pfn_list(iommu);
>               kfree(iommu->external_domain);
>       }
>  

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