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.

For legacy and scalable legacy modes, 48 is the default choice for
modern OS when both 48 and 39 are supported. So it makes sense to
set default to 48 for these two modes too starting from QEMU 9.2.
Use pc_compat_9_1 to handle the compatibility for machines before
9.2.

Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Clément Mathieu--Drif<clement.mathieu--drif@eviden.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
---
 include/hw/i386/intel_iommu.h | 2 +-
 hw/i386/pc.c                  | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/hw/i386/intel_iommu.h b/include/hw/i386/intel_iommu.h
index 13e8680b87..09ce707930 100644
--- a/include/hw/i386/intel_iommu.h
+++ b/include/hw/i386/intel_iommu.h
@@ -45,7 +45,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(IntelIOMMUState, INTEL_IOMMU_DEVICE)
 #define DMAR_REG_SIZE               0x230
 #define VTD_HOST_AW_39BIT           39
 #define VTD_HOST_AW_48BIT           48
-#define VTD_HOST_ADDRESS_WIDTH      VTD_HOST_AW_39BIT
+#define VTD_HOST_ADDRESS_WIDTH      VTD_HOST_AW_48BIT
 #define VTD_HAW_MASK(aw)            ((1ULL << (aw)) - 1)
 
 #define DMAR_REPORT_F_INTR          (1)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 830614d930..bdb67f1fd4 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -83,6 +83,7 @@ GlobalProperty pc_compat_9_1[] = {
     { "ICH9-LPC", "x-smi-swsmi-timer", "off" },
     { "ICH9-LPC", "x-smi-periodic-timer", "off" },
     { TYPE_INTEL_IOMMU_DEVICE, "stale-tm", "on" },
+    { TYPE_INTEL_IOMMU_DEVICE, "aw-bits", "39" },
 };
 const size_t pc_compat_9_1_len = G_N_ELEMENTS(pc_compat_9_1);
 
-- 
2.34.1