Re: [PATCH v3 1/3] qemu: introduce QEMU_CAPS_ARM_SMMUV3_CMDQV

[Nathan Chen via Devel]

Hi Pavel,

On 8/18/2026 1:42 AM, Pavel Hrdina wrote:

On Tue, Aug 11, 2026 at 11:50:44AM -0700, Nathan Chen via Devel wrote:

From: Nathan Chen<nath...@nvidia.com>

Probe the arm-smmuv3 cmdqv device property via device-list-properties,
gated on QEMU_CAPS_DEVICE_ARM_SMMUV3. Reject domain configs that set
cmdqv when the QEMU binary lacks the property.

Signed-off-by: Nathan Chen<nath...@nvidia.com>
---
  src/qemu/qemu_capabilities.c                       | 4 ++++
  src/qemu/qemu_capabilities.h                       | 3 +++
  src/qemu/qemu_validate.c                           | 9 +++++++++
  tests/qemucapabilitiesdata/caps_11.1.0_aarch64.xml | 1 +
  4 files changed, 17 insertions(+)

diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 6abb179951..a0fe9b36a6 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -771,6 +771,9 @@ VIR_ENUM_IMPL(virQEMUCaps,
                "arm-smmuv3", /* QEMU_CAPS_DEVICE_ARM_SMMUV3 */
                "arm-smmuv3.smmu_per_bus", /* QEMU_CAPS_ARM_SMMUV3_SMMU_PER_BUS 
*/
                "arm-smmuv3.accel", /* QEMU_CAPS_ARM_SMMUV3_ACCEL */
+
+              /* 500 */
+              "arm-smmuv3.cmdqv", /* QEMU_CAPS_ARM_SMMUV3_CMDQV */
      );

@@ -1651,6 +1654,7 @@ static struct virQEMUCapsDevicePropsFlags virQEMUCapsDevicePropsAMDIOMMU[] = {

  static struct virQEMUCapsDevicePropsFlags virQEMUCapsDevicePropsArmSmmuv3[] = 
{
      { "smmu_per_bus", QEMU_CAPS_ARM_SMMUV3_SMMU_PER_BUS, NULL },
      { "accel", QEMU_CAPS_ARM_SMMUV3_ACCEL, NULL },
+    { "cmdqv", QEMU_CAPS_ARM_SMMUV3_CMDQV, NULL },
  };

/* see documentation for virQEMUQAPISchemaPathGet for the query format */

diff --git a/src/qemu/qemu_capabilities.h b/src/qemu/qemu_capabilities.h
index 4563e15156..91c4852ea7 100644
--- a/src/qemu/qemu_capabilities.h
+++ b/src/qemu/qemu_capabilities.h
@@ -746,6 +746,9 @@ typedef enum { /* virQEMUCapsFlags grouping marker for 
syntax-check */
      QEMU_CAPS_ARM_SMMUV3_SMMU_PER_BUS, /* arm-smmuv3.smmu_per_bus */
      QEMU_CAPS_ARM_SMMUV3_ACCEL, /* arm-smmuv3.accel */

+ /* 500 */

+    QEMU_CAPS_ARM_SMMUV3_CMDQV, /* arm-smmuv3.cmdqv */
+
      QEMU_CAPS_LAST /* this must always be the last item */
  } virQEMUCapsFlags;

diff --git a/src/qemu/qemu_validate.c b/src/qemu/qemu_validate.c

index 61f3bd3278..25527ca2cc 100644
--- a/src/qemu/qemu_validate.c
+++ b/src/qemu/qemu_validate.c
@@ -5829,6 +5829,15 @@ qemuValidateDomainDeviceDefIOMMU(const virDomainIOMMUDef 
*iommu,
          return -1;
      }

+ /* cmdqv was added after accel; do not treat ACCEL as a proxy for it. */

+    if (iommu->model == VIR_DOMAIN_IOMMU_MODEL_SMMUV3 &&
+        iommu->cmdqv != VIR_TRISTATE_SWITCH_ABSENT &&
+        !virQEMUCapsGet(qemuCaps, QEMU_CAPS_ARM_SMMUV3_CMDQV)) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("iommu: cmdqv is not supported with this QEMU 
binary"));
+        return -1;
+    }
+
      if (iommu->granule > 0) {
          /* QEMU supports only 4KiB, 8KiB, 16KiB and 64KiB granule size */
          if (!(iommu->granule == 4 ||

This check needs to be moved to PATCH 02, otherwise compilation of this
patch fails because iommu->cmdqv is not defined.

Got it, I will make this fix.

Thanks,
Nathan