[PATCH rfcv2 15/17] intel_iommu: Set default aw_bits to 48 in scalable modren mode

[Zhenzhong Duan]

According to VTD spec, stage-1 page table could support 4-level and
5-level paging.

However, 5-level paging translation emulation is unsupported yet.
That means the only supported value for aw_bits is 48.

So default aw_bits to 48 in scalable modern mode. In other cases,
it is still default to 39 for compatibility.

Add a check to ensure user specified value is 48 in modern mode
for now.

Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
---
 hw/i386/intel_iommu.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index e07daaba99..a4c241ea96 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -3748,7 +3748,7 @@ static Property vtd_properties[] = {
                             ON_OFF_AUTO_AUTO),
     DEFINE_PROP_BOOL("x-buggy-eim", IntelIOMMUState, buggy_eim, false),
     DEFINE_PROP_UINT8("aw-bits", IntelIOMMUState, aw_bits,
-                      VTD_HOST_ADDRESS_WIDTH),
+                      0xff),
     DEFINE_PROP_BOOL("caching-mode", IntelIOMMUState, caching_mode, FALSE),
     DEFINE_PROP_BOOL("x-scalable-mode", IntelIOMMUState, scalable_mode, FALSE),
     DEFINE_PROP_BOOL("snoop-control", IntelIOMMUState, snoop_control, false),
@@ -4663,6 +4663,14 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error 
**errp)
         }
     }
 
+    if (s->aw_bits == 0xff) {
+        if (s->scalable_modern) {
+            s->aw_bits = VTD_HOST_AW_48BIT;
+        } else {
+            s->aw_bits = VTD_HOST_AW_39BIT;
+        }
+    }
+
     if ((s->aw_bits != VTD_HOST_AW_39BIT) &&
         (s->aw_bits != VTD_HOST_AW_48BIT) &&
         !s->scalable_modern) {
@@ -4671,6 +4679,12 @@ static bool vtd_decide_config(IntelIOMMUState *s, Error 
**errp)
         return false;
     }
 
+    if ((s->aw_bits != VTD_HOST_AW_48BIT) && s->scalable_modern) {
+        error_setg(errp, "Supported values for aw-bits are: %d",
+                   VTD_HOST_AW_48BIT);
+        return false;
+    }
+
     if (s->scalable_mode && !s->dma_drain) {
         error_setg(errp, "Need to set dma_drain for scalable mode");
         return false;
-- 
2.34.1