[PATCH 1/3] amd-vi: use the same IOMMU page table levels for PV and HVM

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Using different page table levels for HVM or PV guest is not helpful, and is
not inline with the IOMMU implementation used by the other architecture vendor
(VT-d).

Switch to uniformly use DEFAULT_DOMAIN_ADDRESS_WIDTH in order to set the AMD-Vi
page table levels.

Note using the max RAM address for PV was bogus anyway, as there's no guarantee
there can't be device MMIO or reserved regions past the maximum RAM region.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/drivers/passthrough/amd/pci_amd_iommu.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/xen/drivers/passthrough/amd/pci_amd_iommu.c 
b/xen/drivers/passthrough/amd/pci_amd_iommu.c
index 6bc73dc21052..f9e749d74da2 100644
--- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
+++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
@@ -359,21 +359,17 @@ int __read_mostly amd_iommu_min_paging_mode = 1;
 static int cf_check amd_iommu_domain_init(struct domain *d)
 {
     struct domain_iommu *hd = dom_iommu(d);
+    int pgmode = amd_iommu_get_paging_mode(
+        1UL << (DEFAULT_DOMAIN_ADDRESS_WIDTH - PAGE_SHIFT));
+
+    if ( pgmode < 0 )
+        return pgmode;
 
     /*
-     * Choose the number of levels for the IOMMU page tables.
-     * - PV needs 3 or 4, depending on whether there is RAM (including hotplug
-     *   RAM) above the 512G boundary.
-     * - HVM could in principle use 3 or 4 depending on how much guest
-     *   physical address space we give it, but this isn't known yet so use 4
-     *   unilaterally.
-     * - Unity maps may require an even higher number.
+     * Choose the number of levels for the IOMMU page tables, taking into
+     * account unity maps.
      */
-    hd->arch.amd.paging_mode = max(amd_iommu_get_paging_mode(
-            is_hvm_domain(d)
-            ? 1UL << (DEFAULT_DOMAIN_ADDRESS_WIDTH - PAGE_SHIFT)
-            : get_upper_mfn_bound() + 1),
-        amd_iommu_min_paging_mode);
+    hd->arch.amd.paging_mode = max(pgmode, amd_iommu_min_paging_mode);
 
     return 0;
 }
-- 
2.42.0