[PATCH v2 4/7] hw/arm/smmuv3-accel: Implement "auto" value for "ssidsize"

[Nathan Chen <nathanc@nvidia.com>]

Allow accelerated SMMUv3 SSID size property to be derived from host
IOMMU capabilities. Derive host values using IOMMU_GET_HW_INFO,
retrieving SSID size from IDR1. When the auto SSID size is resolved
to a non-zero value, PASID capability is advertised to the vIOMMU
and accelerated use cases such as Shared Virtual Addressing (SVA)
are supported.

Signed-off-by: Nathan Chen <nathanc@nvidia.com>
---
 hw/arm/smmuv3-accel.c | 18 ++++++++++++++++--
 hw/arm/smmuv3.c       | 20 ++++++++++----------
 2 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/hw/arm/smmuv3-accel.c b/hw/arm/smmuv3-accel.c
index 98c2cdcb5e..d13d15a11d 100644
--- a/hw/arm/smmuv3-accel.c
+++ b/hw/arm/smmuv3-accel.c
@@ -62,6 +62,12 @@ static void smmuv3_accel_auto_finalise(SMMUv3State *s,
                                FIELD_EX32(info->idr[3], IDR3, RIL));
     }
 
+    if (s->ssidsize == SSID_SIZE_MODE_AUTO) {
+        /* Store for get_viommu_flags() to determine PASID support */
+        s->idr[1] = FIELD_DP32(s->idr[1], IDR1, SSIDSIZE,
+                               FIELD_EX32(info->idr[1], IDR1, SSIDSIZE));
+    }
+
     accel->auto_finalised = true;
 }
 
@@ -822,6 +828,13 @@ static AddressSpace *smmuv3_accel_find_add_as(PCIBus *bus, void *opaque,
     }
 }
 
+static inline bool smmuv3_pasid_supported(SMMUv3State *s)
+{
+    return s->ssidsize > SSID_SIZE_MODE_0 ||
+           (s->ssidsize == SSID_SIZE_MODE_AUTO &&
+            FIELD_EX32(s->idr[1], IDR1, SSIDSIZE));
+}
+
 static uint64_t smmuv3_accel_get_viommu_flags(void *opaque)
 {
     /*
@@ -834,7 +847,7 @@ static uint64_t smmuv3_accel_get_viommu_flags(void *opaque)
     SMMUState *bs = opaque;
     SMMUv3State *s = ARM_SMMUV3(bs);
 
-    if (s->ssidsize > SSID_SIZE_MODE_0) {
+    if (smmuv3_pasid_supported(s)) {
         flags |= VIOMMU_FLAG_PASID_SUPPORTED;
     }
     return flags;
@@ -974,7 +987,8 @@ void smmuv3_accel_init(SMMUv3State *s)
     smmuv3_accel_as_init(s);
 
     if (s->ats == ON_OFF_AUTO_AUTO ||
-        s->ril == ON_OFF_AUTO_AUTO) {
+        s->ril == ON_OFF_AUTO_AUTO ||
+        s->ssidsize == SSID_SIZE_MODE_AUTO) {
         s->s_accel->auto_mode = true;
     }
 
diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
index b7aa4122eb..07025245e2 100644
--- a/hw/arm/smmuv3.c
+++ b/hw/arm/smmuv3.c
@@ -626,7 +626,10 @@ static int decode_ste(SMMUv3State *s, SMMUTransCfg *cfg,
     }
 
     /* Multiple context descriptors require SubstreamID support */
-    if (s->ssidsize == SSID_SIZE_MODE_0 && STE_S1CDMAX(ste) != 0) {
+    if ((s->ssidsize == SSID_SIZE_MODE_0 ||
+         (s->ssidsize == SSID_SIZE_MODE_AUTO &&
+          !FIELD_EX32(s->idr[1], IDR1, SSIDSIZE))) &&
+        STE_S1CDMAX(ste) != 0) {
         qemu_log_mask(LOG_UNIMP,
                 "SMMUv3: multiple S1 context descriptors require SubstreamID support. "
                 "Configure ssidsize > 0 (requires accel=on)\n");
@@ -1972,10 +1975,6 @@ static bool smmu_validate_property(SMMUv3State *s, Error **errp)
     }
 #endif
 
-    if (s->ssidsize == SSID_SIZE_MODE_AUTO) {
-        error_setg(errp, "ssidsize auto mode is not supported");
-        return false;
-    }
     if (s->oas != OAS_MODE_44 && s->oas != OAS_MODE_48) {
         error_setg(errp, "QEMU SMMUv3 model only implements 44 and 48 bit"
                    "OAS; other OasMode values are not supported");
@@ -1996,7 +1995,8 @@ static bool smmu_validate_property(SMMUv3State *s, Error **errp)
             return false;
         }
         if (s->ssidsize > SSID_SIZE_MODE_0) {
-            error_setg(errp, "ssidsize can only be set if accel=on");
+            error_setg(errp, "ssidsize can only be greater than 0 "
+                       "bits if accel=on");
             return false;
         }
         return true;
@@ -2177,11 +2177,11 @@ static void smmuv3_class_init(ObjectClass *klass, const void *data)
         "are 44 or 48 bits. Defaults to 44 bits. oas=auto is not "
         "supported.");
     object_class_property_set_description(klass, "ssidsize",
-        "Number of bits used to represent SubstreamIDs (SSIDs). "
+        "Set number of bits used to represent SubstreamIDs (SSIDs). "
+        "Valid values are 0-20 and auto. Defaults to 0. "
         "A value of N allows SSIDs in the range [0 .. 2^N - 1]. "
-        "Valid range is 0-20, where 0 disables SubstreamID support. "
-        "Defaults to 0. A value greater than 0 is required to enable "
-        "PASID support. ssidsize=auto is not supported.");
+        "A value of 0 disables SubstreamID support. A value greater "
+        "than 0 is required to enable PASID support.");
 }
 
 static int smmuv3_notify_flag_changed(IOMMUMemoryRegion *iommu,
-- 
2.43.0