[xen stable-4.14] AMD/IOMMU: don't leave page table mapped when unmapping ...

[patchbot@xxxxxxx]

commit 301ea7a89d1a31fd1732d22b5eb3f78058fdd5dc
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Aug 25 15:11:37 2021 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Aug 25 15:11:37 2021 +0200

    AMD/IOMMU: don't leave page table mapped when unmapping ...
    
    ... an already not mapped page. With all other exit paths doing the
    unmap, I have no idea how I managed to miss that aspect at the time.
    
    Fixes: ad591454f069 ("AMD/IOMMU: don't needlessly trigger errors/crashes 
when unmapping a page")
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Paul Durrant <paul@xxxxxxx>
    master commit: 3cfec6a6aa7a7bf68f8e19e21f450c2febe9acb4
    master date: 2021-08-20 12:30:35 +0200
---
 xen/drivers/passthrough/amd/iommu_map.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/drivers/passthrough/amd/iommu_map.c 
b/xen/drivers/passthrough/amd/iommu_map.c
index cf4da2b00a..90c6e8b93e 100644
--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -256,7 +256,10 @@ static int iommu_pde_from_dfn(struct domain *d, unsigned 
long dfn,
         else if ( !pde->pr )
         {
             if ( !map )
+            {
+                unmap_domain_page(next_table_vaddr);
                 return 0;
+            }
 
             if ( next_table_mfn == 0 )
             {
--
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