From: Nathan Chen <nathanc@nvidia.com>

Allow accelerated SMMUv3 OAS property to be derived from host IOMMU
capabilities. Derive host values using IOMMU_GET_HW_INFO, retrieving
OAS from IDR5.

This keeps the OAS value advertised by the virtual SMMU compatible with
the capabilities of the host SMMUv3, so that the intermediate physical
addresses (IPA) consumed by host SMMU for stage-2 translation do not
exceed the host's max supported IPA size.

Signed-off-by: Nathan Chen <nathanc@nvidia.com>
---
 hw/arm/smmuv3-accel.c | 9 ++++++++-
 hw/arm/smmuv3.c       | 6 +++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
index 03393fd7ba..105f6d26bf 100644
--- a/hw/arm/smmuv3-accel.c
+++ b/hw/arm/smmuv3-accel.c
@@ -63,6 +63,12 @@ static void smmuv3_accel_auto_finalise(SMMUv3State *s,
                                FIELD_EX32(info->idr[1], IDR1, SSIDSIZE));
     }
 
+    /* Update OAS if auto from info */
+    if (s->oas == OAS_MODE_AUTO) {
+        s->idr[5] = FIELD_DP32(s->idr[5], IDR5, OAS,
+                               FIELD_EX32(info->idr[5], IDR5, OAS));
+    }
+
     accel->auto_finalised = true;
 }
 
@@ -962,7 +968,8 @@ void smmuv3_accel_init(SMMUv3State *s)
 
     if (s->ats == ON_OFF_AUTO_AUTO ||
         s->ril == ON_OFF_AUTO_AUTO ||
-        s->ssidsize == SSID_SIZE_MODE_AUTO) {
+        s->ssidsize == SSID_SIZE_MODE_AUTO ||
+        s->oas == OAS_MODE_AUTO) {
         s->s_accel->auto_mode = true;
     }
 }
diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
index cb14a08a66..0ab6d1e762 100644
--- a/hw/arm/smmuv3.c
+++ b/hw/arm/smmuv3.c
@@ -1976,7 +1976,8 @@ static bool smmu_validate_property(SMMUv3State *s, Error **errp)
     }
 #endif
 
-    if (s->oas != OAS_MODE_44 && s->oas != OAS_MODE_48) {
+    if (s->oas != OAS_MODE_44 && s->oas != OAS_MODE_48 &&
+        s->oas != OAS_MODE_AUTO) {
         error_setg(errp, "QEMU SMMUv3 model only implements 44 and 48 bit"
                    "OAS; other OasMode values are not supported");
         return false;
@@ -2189,8 +2190,7 @@ static void smmuv3_class_init(ObjectClass *klass, const void *data)
         "platform has ATS support before enabling this.");
     object_class_property_set_description(klass, "oas",
         "Specify Output Address Size (for accel=on). Supported values "
-        "are 44 or 48 bits. Defaults to 44 bits. oas=auto is not "
-        "supported.");
+        "are 44 or 48 bits. Defaults to 44 bits.");
     object_class_property_set_description(klass, "ssidsize",
         "Number of bits used to represent SubstreamIDs (SSIDs). "
         "A value of N allows SSIDs in the range [0 .. 2^N - 1]. "
-- 
2.43.0