AMD IOMMU: don't free page table prematurely

iommu_merge_pages() still wants to look at the next level page table,
the TLB flush necessary before freeing too happens in that function,
and if it fails no free should happen at all. Hence the freeing must
be done after that function returned successfully, not before it's
being called.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
master commit: 6b4d71d028f445cba7426a144751fddc8bfdd67b
master date: 2014-05-28 09:50:33 +0200

diff --git a/xen/drivers/passthrough/amd/iommu_map.c b/xen/drivers/passthrough/amd/iommu_map.c
index 129456111487fe1b6c50ca8c7a2f74c918e30fe2..5e02ac8492fe8e2a38638c0a221de9f802107f16 100644 (file)
--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -691,8 +691,6 @@ int amd_iommu_map_page(struct domain *d, unsigned long gfn, unsigned long mfn,
         if ( !iommu_update_pde_count(d, pt_mfn[merge_level],
                                      gfn, mfn, merge_level) )
             break;
-        /* Deallocate lower level page table */
-        free_amd_iommu_pgtable(mfn_to_page(pt_mfn[merge_level - 1]));
 
         if ( iommu_merge_pages(d, pt_mfn[merge_level], gfn, 
                                flags, merge_level) )
@@ -703,6 +701,9 @@ int amd_iommu_map_page(struct domain *d, unsigned long gfn, unsigned long mfn,
             domain_crash(d);
             return -EFAULT;
         }
+
+        /* Deallocate lower level page table */
+        free_amd_iommu_pgtable(mfn_to_page(pt_mfn[merge_level - 1]));
     }
 
 out: