conf: Allow aw_bits for virtio-iommu

Introduced in QEMU commit of v9.0.0-rc0~9^2~7 the virtio-iommu
device is also capable of using different addres width. The
corresponding attribute is also called 'aw-bits', just like in
case of intel-iommu. Wire up the missing pieces.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>

docs/formatdomain.rst

@@ -9253,7 +9253,7 @@ Example:
    ``aw_bits``
       The ``aw_bits`` attribute can be used to set the address width to allow
       mapping larger iova addresses in the guest. :since:`Since 6.5.0` (QEMU/KVM
-      and ``intel`` model only)
+      and ``intel`` or ``virtio`` models only)
 
    ``dma_translation``
       The ``dma_translation`` attribute with possible values ``on`` and ``off`` can

src/conf/domain_validate.c

@@ -3206,14 +3206,22 @@ virDomainIOMMUDefValidate(const virDomainIOMMUDef *iommu)
             iommu->caching_mode != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->eim != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->iotlb != VIR_TRISTATE_SWITCH_ABSENT ||
-            iommu->aw_bits != 0 ||
             iommu->dma_translation != VIR_TRISTATE_SWITCH_ABSENT ||
             iommu->pci_bus >= 0) {
             virReportError(VIR_ERR_XML_ERROR,
-                           _("iommu model '%1$s' doesn't support additional attributes"),
+                           _("iommu model '%1$s' doesn't support some additional attributes"),
                            virDomainIOMMUModelTypeToString(iommu->model));
             return -1;
         }
+
+        /* QEMU mandates address width of the IOVA address space to be inside
+         * [32,64] range, but since it stems from virtio specification it can
+         * be assumed to be hypervisor agnostic and thus can live here. */
+        if (iommu->aw_bits != 0 && (iommu->aw_bits < 32 || iommu->aw_bits > 64)) {
+            virReportError(VIR_ERR_XML_ERROR, "%s",
+                           _("aw-bits must be within [32,64]"));
+            return -1;
+        }
         break;
 
     case VIR_DOMAIN_IOMMU_MODEL_AMD:

src/qemu/qemu_validate.c

@@ -5552,6 +5552,8 @@ qemuValidateDomainDeviceDefIOMMU(const virDomainIOMMUDef *iommu,
                                  const virDomainDef *def,
                                  virQEMUCaps *qemuCaps)
 {
+    bool aw_bits_supported = false;
+
     switch (iommu->model) {
     case VIR_DOMAIN_IOMMU_MODEL_INTEL:
         if (!qemuDomainIsQ35(def)) {
@@ -5566,6 +5568,7 @@ qemuValidateDomainDeviceDefIOMMU(const virDomainIOMMUDef *iommu,
                            virDomainIOMMUModelTypeToString(iommu->model));
             return -1;
         }
+        aw_bits_supported = virQEMUCapsGet(qemuCaps, QEMU_CAPS_INTEL_IOMMU_AW_BITS);
         break;
 
     case VIR_DOMAIN_IOMMU_MODEL_SMMUV3:
@@ -5611,6 +5614,7 @@ qemuValidateDomainDeviceDefIOMMU(const virDomainIOMMUDef *iommu,
                            virDomainIOMMUModelTypeToString(iommu->model));
             return -1;
         }
+        aw_bits_supported = virQEMUCapsGet(qemuCaps, QEMU_CAPS_VIRTIO_IOMMU_AW_BITS);
         break;
 
     case VIR_DOMAIN_IOMMU_MODEL_AMD:
@@ -5670,8 +5674,7 @@ qemuValidateDomainDeviceDefIOMMU(const virDomainIOMMUDef *iommu,
                        _("iommu: device IOTLB is not supported with this QEMU binary"));
         return -1;
     }
-    if (iommu->aw_bits > 0 &&
-        !virQEMUCapsGet(qemuCaps, QEMU_CAPS_INTEL_IOMMU_AW_BITS)) {
+    if (iommu->aw_bits > 0 && !aw_bits_supported) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                        _("iommu: aw_bits is not supported with this QEMU binary"));
         return -1;

tests/qemuxmlconfdata/virtio-iommu-aarch64.aarch64-latest.xml

@@ -29,6 +29,7 @@
     <audio id='1' type='none'/>
     <memballoon model='none'/>
     <iommu model='virtio'>
+      <driver aw_bits='48'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
     </iommu>
   </devices>

tests/qemuxmlconfdata/virtio-iommu-aarch64.xml

@@ -13,6 +13,8 @@
     <emulator>/usr/bin/qemu-system-aarch64</emulator>
     <controller type='usb' model='none'/>
     <memballoon model='none'/>
-    <iommu model='virtio'/>
+    <iommu model='virtio'>
+      <driver aw_bits='48'/>
+    </iommu>
   </devices>
 </domain>

tests/qemuxmlconfdata/virtio-iommu-dma-translation.x86_64-latest.err

@@ -1 +1 @@
-XML error: iommu model 'virtio' doesn't support additional attributes
+XML error: iommu model 'virtio' doesn't support some additional attributes