File 5dca84a2-AMD-IOMMU-dont-needlessly-trigger-erro... of Package xen

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File 5dca84a2-AMD-IOMMU-dont-needlessly-trigger-errors-on-unmap.patch of Package xen (Revision a90efdcc88577026ef2a13678bb8ab98)

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# Commit ad591454f069647c36a7daaa9ec23384c0263f0b
# Date 2019-11-12 11:08:34 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
AMD/IOMMU: don't needlessly trigger errors/crashes when unmapping a page

Unmapping a page which has never been mapped should be a no-op (note how
it already is in case there was no root page table allocated). There's
in particular no need to grow the number of page table levels in use,
and there's also no need to allocate intermediate page tables except
when needing to split a large page.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul@xen.org>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -343,7 +343,7 @@ uint64_t amd_iommu_get_address_from_pte(
  * page tables.
  */
 static int iommu_pde_from_dfn(struct domain *d, unsigned long dfn,
-                              unsigned long pt_mfn[])
+                              unsigned long pt_mfn[], bool map)
 {
     uint64_t *pde, *next_table_vaddr;
     unsigned long  next_table_mfn;
@@ -356,6 +356,13 @@ static int iommu_pde_from_dfn(struct dom
 
     BUG_ON( table == NULL || level < 1 || level > 6 );
 
+    /*
+     * A frame number past what the current page tables can represent can't
+     * possibly have a mapping.
+     */
+    if ( dfn >> (PTE_PER_TABLE_SHIFT * level) )
+        return 0;
+
     next_table_mfn = mfn_x(page_to_mfn(table));
 
     if ( level == 1 )
@@ -415,6 +422,9 @@ static int iommu_pde_from_dfn(struct dom
         /* Install lower level page table for non-present entries */
         else if ( !iommu_is_pte_present((uint32_t *)pde) )
         {
+            if ( !map )
+                return 0;
+
             if ( next_table_mfn == 0 )
             {
                 table = alloc_amd_iommu_pgtable();
@@ -577,7 +587,7 @@ int amd_iommu_map_page(struct domain *d,
         }
     }
 
-    if ( iommu_pde_from_dfn(d, dfn_x(dfn), pt_mfn) || (pt_mfn[1] == 0) )
+    if ( iommu_pde_from_dfn(d, dfn_x(dfn), pt_mfn, true) || (pt_mfn[1] == 0) )
     {
         spin_unlock(&hd->arch.mapping_lock);
         AMD_IOMMU_DEBUG("Invalid IO pagetable entry dfn = %"PRI_dfn"\n",
@@ -615,24 +625,7 @@ int amd_iommu_unmap_page(struct domain *
         return 0;
     }
 
-    /* Since HVM domain is initialized with 2 level IO page table,
-     * we might need a deeper page table for lager dfn now */
-    if ( is_hvm_domain(d) )
-    {
-        int rc = update_paging_mode(d, dfn_x(dfn));
-
-        if ( rc )
-        {
-            spin_unlock(&hd->arch.mapping_lock);
-            AMD_IOMMU_DEBUG("Update page mode failed dfn = %"PRI_dfn"\n",
-                            dfn_x(dfn));
-            if ( rc != -EADDRNOTAVAIL )
-                domain_crash(d);
-            return rc;
-        }
-    }
-
-    if ( iommu_pde_from_dfn(d, dfn_x(dfn), pt_mfn) || (pt_mfn[1] == 0) )
+    if ( iommu_pde_from_dfn(d, dfn_x(dfn), pt_mfn, false) )
     {
         spin_unlock(&hd->arch.mapping_lock);
         AMD_IOMMU_DEBUG("Invalid IO pagetable entry dfn = %"PRI_dfn"\n",
@@ -641,8 +634,11 @@ int amd_iommu_unmap_page(struct domain *
         return -EFAULT;
     }
 
-    /* mark PTE as 'page not present' */
-    *flush_flags |= clear_iommu_pte_present(pt_mfn[1], dfn_x(dfn));
+    if ( pt_mfn[1] )
+    {
+        /* Mark PTE as 'page not present'. */
+        *flush_flags |= clear_iommu_pte_present(pt_mfn[1], dfn_x(dfn));
+    }
 
     spin_unlock(&hd->arch.mapping_lock);

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File 5dca84a2-AMD-IOMMU-dont-needlessly-trigger-errors-on-unmap.patch of Package xen (Revision a90efdcc88577026ef2a13678bb8ab98)

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