On 11/20/25 14:22, Shameer Kolothum wrote:
Introduce an “accel” property to enable accelerator mode.
Live migration is currently unsupported when accelerator mode is enabled,
so a migration blocker is added.
Because this mode relies on IORT RMR for MSI support, accelerator mode is
not supported for device tree boot.
Also, in the accelerated SMMUv3 case, the host SMMUv3 is configured in nested
mode (S1 + S2), and the guest owns the Stage-1 page table. Therefore, we
expose only Stage-1 to the guest to ensure it uses the correct page table
format.
Reviewed-by: Nicolin Chen <[email protected]>
Reviewed-by: Eric Auger <[email protected]>
Tested-by: Zhangfei Gao <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Signed-off-by: Shameer Kolothum <[email protected]>
---
hw/arm/smmuv3.c | 26 ++++++++++++++++++++++++++
hw/arm/virt-acpi-build.c | 4 +---
hw/arm/virt.c | 15 +++++++++++----
include/hw/arm/smmuv3.h | 1 +
4 files changed, 39 insertions(+), 7 deletions(-)
diff --git a/hw/arm/smmuv3.c b/hw/arm/smmuv3.c
index dba5abc8d3..8352dd5757 100644
--- a/hw/arm/smmuv3.c
+++ b/hw/arm/smmuv3.c
@@ -20,6 +20,7 @@
#include "qemu/bitops.h"
#include "hw/irq.h"
#include "hw/sysbus.h"
+#include "migration/blocker.h"
#include "migration/vmstate.h"
#include "hw/qdev-properties.h"
#include "hw/qdev-core.h"
@@ -1915,6 +1916,17 @@ static void smmu_reset_exit(Object *obj, ResetType type)
smmuv3_accel_reset(s);
}
+static bool smmu_validate_property(SMMUv3State *s, Error **errp)
+{
+#ifndef CONFIG_ARM_SMMUV3_ACCEL
+ if (s->accel) {
+ error_setg(errp, "accel=on support not compiled in");
+ return false;
+ }
+#endif
+ return true;
+}
+
static void smmu_realize(DeviceState *d, Error **errp)
{
SMMUState *sys = ARM_SMMU(d);
@@ -1923,8 +1935,17 @@ static void smmu_realize(DeviceState *d, Error **errp)
SysBusDevice *dev = SYS_BUS_DEVICE(d);
Error *local_err = NULL;
+ if (!smmu_validate_property(s, errp)) {
+ return;
+ }
You should really consider adding a new QOM model for the "accel" mode.
if (s->accel) {
smmuv3_accel_init(s);
+ error_setg(&s->migration_blocker, "Migration not supported with SMMUv3
"
+ "accelerator mode enabled");
+ if (migrate_add_blocker(&s->migration_blocker, errp) < 0) {
+ return;
+ }
I would add the migration blocker in a separate patch.
}
c->parent_realize(d, &local_err);
@@ -2023,6 +2044,7 @@ static const Property smmuv3_properties[] = {
* Defaults to stage 1
*/
DEFINE_PROP_STRING("stage", SMMUv3State, stage),
+ DEFINE_PROP_BOOL("accel", SMMUv3State, accel, false),
/* GPA of MSI doorbell, for SMMUv3 accel use. */
DEFINE_PROP_UINT64("msi-gpa", SMMUv3State, msi_gpa, 0),
};
@@ -2046,6 +2068,10 @@ static void smmuv3_class_init(ObjectClass *klass, const
void *data)
device_class_set_props(dc, smmuv3_properties);
dc->hotpluggable = false;
dc->user_creatable = true;
+
+ object_class_property_set_description(klass, "accel",
+ "Enable SMMUv3 accelerator support. Allows host SMMUv3 to be "
+ "configured in nested mode for vfio-pci dev assignment");
}
static int smmuv3_notify_flag_changed(IOMMUMemoryRegion *iommu,
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c
index 7a7b2e62c1..fd78c39317 100644
--- a/hw/arm/virt-acpi-build.c
+++ b/hw/arm/virt-acpi-build.c
@@ -400,9 +400,7 @@ static int iort_smmuv3_devices(Object *obj, void *opaque)
}
bus = PCI_BUS(object_property_get_link(obj, "primary-bus", &error_abort));
- if (object_property_find(obj, "accel")) {
- sdev.accel = object_property_get_bool(obj, "accel", &error_abort);
- }
+ sdev.accel = object_property_get_bool(obj, "accel", &error_abort);
pbus = PLATFORM_BUS_DEVICE(vms->platform_bus_dev);
sbdev = SYS_BUS_DEVICE(obj);
sdev.base = platform_bus_get_mmio_addr(pbus, sbdev, 0);
diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 8503879c3d..51b15aef37 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -3052,13 +3052,21 @@ static void
virt_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
/* The new SMMUv3 device is specific to the PCI bus */
object_property_set_bool(OBJECT(dev), "smmu_per_bus", true, NULL);
}
- if (object_property_find(OBJECT(dev), "accel") &&
- object_property_get_bool(OBJECT(dev), "accel", &error_abort)) {
+ if (object_property_get_bool(OBJECT(dev), "accel", &error_abort)) {
+ char *stage;
+
if (!kvm_enabled() || !kvm_irqchip_in_kernel()) {
error_setg(errp, "SMMUv3 accel=on requires KVM with "
"kernel-irqchip=on support");
return;
}
+ stage = object_property_get_str(OBJECT(dev), "stage",
&error_fatal);
+ /* If no stage specified, SMMUv3 will default to stage 1 */
+ if (*stage && strcmp("1", stage)) {
It would be less "ugly" to check SMMUStage enum values instead
of using string compare :/
+ error_setg(errp, "Only stage1 is supported for SMMUV3 with "
+ "accel=on");
Can't this condition be checked in the realize handler instead ?
C.
+ return;
+ }
}
}
}
@@ -3096,8 +3104,7 @@ static void virt_machine_device_plug_cb(HotplugHandler
*hotplug_dev,
}
create_smmuv3_dev_dtb(vms, dev, bus);
- if (object_property_find(OBJECT(dev), "accel") &&
- object_property_get_bool(OBJECT(dev), "accel", &error_abort)) {
+ if (object_property_get_bool(OBJECT(dev), "accel", &error_abort)) {
hwaddr db_start;
if (vms->msi_controller == VIRT_MSI_CTRL_ITS) {
diff --git a/include/hw/arm/smmuv3.h b/include/hw/arm/smmuv3.h
index 5616a8a2be..9c39acd5ca 100644
--- a/include/hw/arm/smmuv3.h
+++ b/include/hw/arm/smmuv3.h
@@ -68,6 +68,7 @@ struct SMMUv3State {
bool accel;
struct SMMUv3AccelState *s_accel;
uint64_t msi_gpa;
+ Error *migration_blocker;
};
typedef enum {
