Re: [PATCH v2 2/2] vfio/iommu_type1: Sanity check pfn_list when remove vfio_dma
From: Alex Williamson <hidden>
Date: 2021-01-15 19:16:40
Also in:
kvmarm, linux-arm-kernel, linux-iommu, lkml
On Fri, 15 Jan 2021 17:26:43 +0800 Keqian Zhu [off-list ref] wrote:
vfio_sanity_check_pfn_list() is used to check whether pfn_list of vfio_dma is empty when remove the external domain, so it makes a wrong assumption that only external domain will add pfn to dma pfn_list. Now we apply this check when remove a specific vfio_dma and extract the notifier check just for external domain.
The page pinning interface is gated by having a notifier registered for
unmaps, therefore non-external domains would also need to register a
notifier. There's currently no other way to add entries to the
pfn_list. So if we allow pinning for such domains, then it's wrong to
WARN_ON() when the notifier list is not-empty when removing an external
domain. Long term we should probably extend page {un}pinning for the
caller to pass their notifier to be validated against the notifier list
rather than just allowing page pinning if *any* notifier is registered.
Thanks,
Alex
quoted hunk ↗ jump to hunk
Fixes: a54eb55045ae ("vfio iommu type1: Add support for mediated devices") Signed-off-by: Keqian Zhu <redacted> --- drivers/vfio/vfio_iommu_type1.c | 24 +++++------------------- 1 file changed, 5 insertions(+), 19 deletions(-)diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 4e82b9a3440f..a9bc15e84a4e 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c@@ -958,6 +958,7 @@ 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);@@ -2251,23 +2252,6 @@ 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@@ -2367,7 +2351,8 @@ 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); + /* mdev vendor driver must unregister notifier */ + WARN_ON(iommu->notifier.head); if (!IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu)) vfio_iommu_unmap_unpin_all(iommu);@@ -2491,7 +2476,8 @@ static void vfio_iommu_type1_release(void *iommu_data) if (iommu->external_domain) { vfio_release_domain(iommu->external_domain, true); - vfio_sanity_check_pfn_list(iommu); + /* mdev vendor driver must unregister notifier */ + WARN_ON(iommu->notifier.head); kfree(iommu->external_domain); }