[libvirt] [PATCH v2 1/2] qemu: support for kvm-hint-dedicated performance hint
Menno Lageman
menno.lageman at oracle.com
Mon Aug 12 12:30:29 UTC 2019
From: Wim ten Have <wim.ten.have at oracle.com>
QEMU version 2.12.1 introduced a performance feature under commit
be7773268d98 ("target-i386: add KVM_HINTS_DEDICATED performance hint")
This patch adds a new KVM feature 'hint-dedicated' to set this performance
hint for KVM guests. The feature is off by default.
To enable this hint and have libvirt add "-cpu host,kvm-hint-dedicated=on"
to the QEMU command line, the following XML code needs to be added to the
guest's domain description in conjunction with CPU mode='host-passthrough'.
<features>
<kvm>
<hint-dedicated state='on'/>
</kvm>
</features>
...
<cpu mode='host-passthrough ... />
Signed-off-by: Wim ten Have <wim.ten.have at oracle.com>
Signed-off-by: Menno Lageman <menno.lageman at oracle.com>
---
docs/formatdomain.html.in | 7 +++++++
docs/schemas/domaincommon.rng | 5 +++++
src/conf/domain_conf.c | 4 ++++
src/conf/domain_conf.h | 1 +
src/qemu/qemu_command.c | 5 +++++
src/qemu/qemu_domain.c | 11 ++++++++++-
6 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 6d084d7c0472..a18119f9a08e 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -2044,6 +2044,7 @@
</hyperv>
<kvm>
<hidden state='on'/>
+ <hint-dedicated state='on'/>
</kvm>
<pvspinlock state='on'/>
<gic version='2'/>
@@ -2217,6 +2218,12 @@
<td>on, off</td>
<td><span class="since">1.2.8 (QEMU 2.1.0)</span></td>
</tr>
+ <tr>
+ <td>hint-dedicated</td>
+ <td>Allows a guest to enable optimizations when running on dedicated vCPUs</td>
+ <td>on, off</td>
+ <td><span class="since">5.7.0 (QEMU 2.12.1)</span></td>
+ </tr>
</table>
</dd>
<dt><code>pmu</code></dt>
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index a0771da45b5d..08853f9d9e92 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -5965,6 +5965,11 @@
<ref name="featurestate"/>
</element>
</optional>
+ <optional>
+ <element name="hint-dedicated">
+ <ref name="featurestate"/>
+ </element>
+ </optional>
</interleave>
</element>
</define>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 03312afaaff8..3907fcf6e5ca 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -202,6 +202,7 @@ VIR_ENUM_IMPL(virDomainHyperv,
VIR_ENUM_IMPL(virDomainKVM,
VIR_DOMAIN_KVM_LAST,
"hidden",
+ "hint-dedicated",
);
VIR_ENUM_IMPL(virDomainMsrsUnknown,
@@ -20412,6 +20413,7 @@ virDomainDefParseXML(xmlDocPtr xml,
switch ((virDomainKVM) feature) {
case VIR_DOMAIN_KVM_HIDDEN:
+ case VIR_DOMAIN_KVM_DEDICATED:
if (!(tmp = virXMLPropString(nodes[i], "state"))) {
virReportError(VIR_ERR_XML_ERROR,
_("missing 'state' attribute for "
@@ -22624,6 +22626,7 @@ virDomainDefFeaturesCheckABIStability(virDomainDefPtr src,
for (i = 0; i < VIR_DOMAIN_KVM_LAST; i++) {
switch ((virDomainKVM) i) {
case VIR_DOMAIN_KVM_HIDDEN:
+ case VIR_DOMAIN_KVM_DEDICATED:
if (src->kvm_features[i] != dst->kvm_features[i]) {
virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
_("State of KVM feature '%s' differs: "
@@ -28124,6 +28127,7 @@ virDomainDefFormatFeatures(virBufferPtr buf,
for (j = 0; j < VIR_DOMAIN_KVM_LAST; j++) {
switch ((virDomainKVM) j) {
case VIR_DOMAIN_KVM_HIDDEN:
+ case VIR_DOMAIN_KVM_DEDICATED:
if (def->kvm_features[j])
virBufferAsprintf(&childBuf, "<%s state='%s'/>\n",
virDomainKVMTypeToString(j),
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index bce47443c858..f7423b1b6f89 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1765,6 +1765,7 @@ typedef enum {
typedef enum {
VIR_DOMAIN_KVM_HIDDEN = 0,
+ VIR_DOMAIN_KVM_DEDICATED,
VIR_DOMAIN_KVM_LAST
} virDomainKVM;
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 71a36ff63a81..f096e8f27e58 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -7212,6 +7212,11 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
virBufferAddLit(&buf, ",kvm=off");
break;
+ case VIR_DOMAIN_KVM_DEDICATED:
+ if (def->kvm_features[i] == VIR_TRISTATE_SWITCH_ON)
+ virBufferAddLit(&buf, ",kvm-hint-dedicated=on");
+ break;
+
/* coverity[dead_error_begin] */
case VIR_DOMAIN_KVM_LAST:
break;
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 937b461a8b55..b9c5a4e54108 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -4449,6 +4449,16 @@ qemuDomainDefValidateFeatures(const virDomainDef *def,
}
break;
+ case VIR_DOMAIN_FEATURE_KVM:
+ if (def->kvm_features[VIR_DOMAIN_KVM_DEDICATED] == VIR_TRISTATE_SWITCH_ON &&
+ (!def->cpu || def->cpu->mode != VIR_CPU_MODE_HOST_PASSTHROUGH)) {
+ virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+ _("kvm-hint-dedicated=on is only applicable "
+ "for cpu host-passthrough"));
+ return -1;
+ }
+ break;
+
case VIR_DOMAIN_FEATURE_ACPI:
case VIR_DOMAIN_FEATURE_APIC:
case VIR_DOMAIN_FEATURE_PAE:
@@ -4456,7 +4466,6 @@ qemuDomainDefValidateFeatures(const virDomainDef *def,
case VIR_DOMAIN_FEATURE_VIRIDIAN:
case VIR_DOMAIN_FEATURE_PRIVNET:
case VIR_DOMAIN_FEATURE_HYPERV:
- case VIR_DOMAIN_FEATURE_KVM:
case VIR_DOMAIN_FEATURE_PVSPINLOCK:
case VIR_DOMAIN_FEATURE_CAPABILITIES:
case VIR_DOMAIN_FEATURE_PMU:
--
2.21.0
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