File xsa378-0b.patch of Package xen.26345

# Commit b75b3c62fe4afe381c6f74a07f614c0b39fe2f5d
# Date 2020-03-16 11:24:29 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
AMD/IOMMU: fix off-by-one in get_paging_mode() callers

amd_iommu_get_paging_mode() expects a count, not a "maximum possible"
value. Prior to b4f042236ae0 dropping the reference, the use of our mis-
named "max_page" in amd_iommu_domain_init() may have lead to such a
misunderstanding. In an attempt to avoid such confusion in the future,
rename the function's parameter and - while at it - convert it to an
inline function.

Also replace a literal 4 by an expression tying it to a wider use
constant, just like amd_iommu_quarantine_init() does.

Fixes: b4f042236ae0 ("AMD/IOMMU: Cease using a dynamic height for the IOMMU pagetables")
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -222,15 +222,15 @@ static int __must_check allocate_domain_
     return rc;
 }
 
-static int get_paging_mode(unsigned long entries)
+static int get_paging_mode(unsigned long max_frames)
 {
     int level = 1;
 
-    BUG_ON( !entries );
+    BUG_ON(!max_frames);
 
-    while ( entries > PTE_PER_TABLE_SIZE )
+    while ( max_frames > PTE_PER_TABLE_SIZE )
     {
-        entries = PTE_PER_TABLE_ALIGN(entries) >> PTE_PER_TABLE_SHIFT;
+        max_frames = PTE_PER_TABLE_ALIGN(max_frames) >> PTE_PER_TABLE_SHIFT;
         if ( ++level > 6 )
             return -ENOMEM;
     }
@@ -250,8 +250,10 @@ static int amd_iommu_domain_init(struct
      *   physical address space we give it, but this isn't known yet so use 4
      *   unilaterally.
      */
-    hd->arch.paging_mode = is_hvm_domain(d)
-        ? IOMMU_PAGING_MODE_LEVEL_4 : get_paging_mode(get_upper_mfn_bound());
+    hd->arch.paging_mode = get_paging_mode(
+        is_hvm_domain(d)
+        ? 1ul << (DEFAULT_DOMAIN_ADDRESS_WIDTH - PAGE_SHIFT)
+        : get_upper_mfn_bound() + 1);
 
     return 0;
 }