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  3. [PATCH 0/2] Add support for new hv enlightenments
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[PATCH 1/2] hyperv: Support hv-emsr-bitmap enlightenment

Tim Wiederhake posted 2 patches 3 months, 1 week ago
[PATCH 1/2] hyperv: Support hv-emsr-bitmap enlightenment
Posted by Tim Wiederhake 3 months, 1 week ago 
qemu supports this enlightenment since version 7.10.

From the qemu commit:
    The newly introduced enlightenment allow L0 (KVM) and L1 (Hyper-V)
    hypervisors to collaborate to avoid unnecessary updates to L2
    MSR-Bitmap upon vmexits.

Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
---
 docs/formatdomain.rst                              | 2 ++
 src/conf/domain_conf.c                             | 4 ++++
 src/conf/domain_conf.h                             | 1 +
 src/conf/schemas/domaincommon.rng                  | 5 +++++
 src/cpu/cpu_x86.c                                  | 4 ++++
 src/cpu/cpu_x86_data.h                             | 1 +
 src/qemu/qemu_command.c                            | 5 +++++
 src/qemu/qemu_process.c                            | 1 +
 tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_8.0.0.x86_64.xml         | 1 +
 tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_8.1.0.x86_64.xml         | 1 +
 tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_8.2.0.x86_64.xml         | 1 +
 tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_9.0.0.x86_64.xml         | 1 +
 tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml     | 1 +
 tests/domaincapsdata/qemu_9.1.0.x86_64.xml         | 1 +
 tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml   | 1 +
 tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml   | 1 +
 tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml   | 1 +
 tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml   | 1 +
 tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml   | 1 +
 tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml | 1 +
 tests/qemuxmlconfdata/hyperv-off.xml               | 1 +
 tests/qemuxmlconfdata/hyperv.x86_64-latest.args    | 2 +-
 tests/qemuxmlconfdata/hyperv.x86_64-latest.xml     | 1 +
 tests/qemuxmlconfdata/hyperv.xml                   | 1 +
 33 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index e1e219bcb5..0cf3dc9deb 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -1989,6 +1989,7 @@ Hypervisors may allow certain CPU / machine features to be toggled on/off.
        <tlbflush state='on'/>
        <ipi state='on'/>
        <evmcs state='on'/>
+       <emsr_bitmap state='on'/>
      </hyperv>
      <kvm>
        <hidden state='on'/>
@@ -2076,6 +2077,7 @@ are:
    ipi             Enable PV IPI support                                                  on, off                                      :since:`4.10.0 (QEMU 3.1)`
    evmcs           Enable Enlightened VMCS                                                on, off                                      :since:`4.10.0 (QEMU 3.1)`
    avic            Enable use Hyper-V SynIC with hardware APICv/AVIC                      on, off                                      :since:`8.10.0 (QEMU 6.2)`
+   emsr_bitmap     Avoid unnecessary updates to L2 MSR Bitmap upon vmexits.               on, off                                      :since:`10.7.0 (QEMU 7.1)`
    =============== ====================================================================== ============================================ =======================================================
 
    :since:`Since 8.0.0`, the hypervisor can be configured further by setting
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index d950921667..c88e885d07 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -211,6 +211,7 @@ VIR_ENUM_IMPL(virDomainHyperv,
               "ipi",
               "evmcs",
               "avic",
+              "emsr_bitmap",
 );
 
 VIR_ENUM_IMPL(virDomainKVM,
@@ -16574,6 +16575,7 @@ virDomainFeaturesHyperVDefParse(virDomainDef *def,
         case VIR_DOMAIN_HYPERV_IPI:
         case VIR_DOMAIN_HYPERV_EVMCS:
         case VIR_DOMAIN_HYPERV_AVIC:
+        case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
             break;
 
         case VIR_DOMAIN_HYPERV_STIMER:
@@ -21020,6 +21022,7 @@ virDomainDefFeaturesCheckABIStability(virDomainDef *src,
             case VIR_DOMAIN_HYPERV_IPI:
             case VIR_DOMAIN_HYPERV_EVMCS:
             case VIR_DOMAIN_HYPERV_AVIC:
+            case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
                 if (src->hyperv_features[i] != dst->hyperv_features[i]) {
                     virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                                    _("State of HyperV enlightenment feature '%1$s' differs: source: '%2$s', destination: '%3$s'"),
@@ -27761,6 +27764,7 @@ virDomainDefFormatFeatures(virBuffer *buf,
                 case VIR_DOMAIN_HYPERV_IPI:
                 case VIR_DOMAIN_HYPERV_EVMCS:
                 case VIR_DOMAIN_HYPERV_AVIC:
+                case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
                     virBufferAddLit(&childBuf, "/>\n");
                     break;
 
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index eae621f900..332bcd0cf9 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -2203,6 +2203,7 @@ typedef enum {
     VIR_DOMAIN_HYPERV_IPI,
     VIR_DOMAIN_HYPERV_EVMCS,
     VIR_DOMAIN_HYPERV_AVIC,
+    VIR_DOMAIN_HYPERV_EMSR_BITMAP,
 
     VIR_DOMAIN_HYPERV_LAST
 } virDomainHyperv;
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index 05ba697924..6f81fc94c2 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -7962,6 +7962,11 @@
                 <ref name="featurestate"/>
               </element>
             </optional>
+            <optional>
+              <element name="emsr_bitmap">
+                <ref name="featurestate"/>
+              </element>
+            </optional>
           </interleave>
         </group>
       </choice>
diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index fcbce0ec46..139ac48234 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -107,6 +107,9 @@ KVM_FEATURE_DEF(VIR_CPU_x86_HV_IPI,
 KVM_FEATURE_DEF(VIR_CPU_x86_HV_EVMCS,
                 0x40000004, 0x00004000, 0x0);
 
+KVM_FEATURE_DEF(VIR_CPU_x86_HV_EMSR_BITMAP,
+                0x4000000A, 0x00080000, 0x0);
+
 static virCPUx86Feature x86_kvm_features[] =
 {
     KVM_FEATURE(VIR_CPU_x86_KVM_PV_UNHALT),
@@ -124,6 +127,7 @@ static virCPUx86Feature x86_kvm_features[] =
     KVM_FEATURE(VIR_CPU_x86_HV_IPI),
     KVM_FEATURE(VIR_CPU_x86_HV_EVMCS),
     KVM_FEATURE(VIR_CPU_x86_HV_STIMER_DIRECT),
+    KVM_FEATURE(VIR_CPU_x86_HV_EMSR_BITMAP),
 };
 
 typedef struct _virCPUx86Signature virCPUx86Signature;
diff --git a/src/cpu/cpu_x86_data.h b/src/cpu/cpu_x86_data.h
index d1ca63db6d..414643fe8d 100644
--- a/src/cpu/cpu_x86_data.h
+++ b/src/cpu/cpu_x86_data.h
@@ -62,6 +62,7 @@ struct _virCPUx86MSR {
 #define VIR_CPU_x86_HV_IPI       "hv-ipi"
 #define VIR_CPU_x86_HV_EVMCS     "hv-evmcs"
 #define VIR_CPU_x86_HV_AVIC      "hv-avic"
+#define VIR_CPU_x86_HV_EMSR_BITMAP "hv-emsr_bitmap"
 
 /* Hyper-V Synthetic Timer option */
 #define VIR_CPU_x86_HV_STIMER_DIRECT "hv-stimer-direct"
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 28914c9c34..cac6fc57a5 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -6523,6 +6523,11 @@ qemuBuildCpuCommandLine(virCommand *cmd,
                                       def->hyperv_vendor_id);
                 break;
 
+            case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
+                if (def->hyperv_features[i] == VIR_TRISTATE_SWITCH_ON)
+                    virBufferAsprintf(&buf, ",%s=on", "hv-emsr-bitmap");
+                break;
+
             case VIR_DOMAIN_HYPERV_LAST:
                 break;
             }
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index a69878e8bb..4a2e3b11fd 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -4304,6 +4304,7 @@ qemuProcessVerifyHypervFeatures(virDomainDef *def,
         case VIR_DOMAIN_HYPERV_IPI:
         case VIR_DOMAIN_HYPERV_EVMCS:
         case VIR_DOMAIN_HYPERV_AVIC:
+        case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                            _("host doesn't support hyperv '%1$s' feature"),
                            virDomainHypervTypeToString(i));
diff --git a/tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml b/tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml
index 8eda04948f..1dfbf98248 100644
--- a/tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml
@@ -285,6 +285,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml b/tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml
index c2d537b520..516eade95b 100644
--- a/tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml
@@ -287,6 +287,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.0.0.x86_64.xml b/tests/domaincapsdata/qemu_8.0.0.x86_64.xml
index 7167406453..96cfc5776e 100644
--- a/tests/domaincapsdata/qemu_8.0.0.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.0.0.x86_64.xml
@@ -285,6 +285,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml b/tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml
index bac0b06683..5bb1299fb1 100644
--- a/tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml
@@ -288,6 +288,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml b/tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml
index 6c455f7ab9..743a6e728b 100644
--- a/tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml
@@ -289,6 +289,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.1.0.x86_64.xml b/tests/domaincapsdata/qemu_8.1.0.x86_64.xml
index f103da3010..fa635fd12b 100644
--- a/tests/domaincapsdata/qemu_8.1.0.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.1.0.x86_64.xml
@@ -288,6 +288,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml b/tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml
index 784c44219c..6c394ba3c4 100644
--- a/tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml
@@ -290,6 +290,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml b/tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml
index 4be710044d..7ebd3ced3a 100644
--- a/tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml
@@ -289,6 +289,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_8.2.0.x86_64.xml b/tests/domaincapsdata/qemu_8.2.0.x86_64.xml
index 2cdf516964..1db706ef7e 100644
--- a/tests/domaincapsdata/qemu_8.2.0.x86_64.xml
+++ b/tests/domaincapsdata/qemu_8.2.0.x86_64.xml
@@ -290,6 +290,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml b/tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml
index 670314ba3e..4fb0ebc45f 100644
--- a/tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml
+++ b/tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml
@@ -290,6 +290,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml b/tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml
index 13afe99cdb..43ff5c3d9f 100644
--- a/tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml
+++ b/tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml
@@ -291,6 +291,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_9.0.0.x86_64.xml b/tests/domaincapsdata/qemu_9.0.0.x86_64.xml
index 71c05e0e97..86edbec0dd 100644
--- a/tests/domaincapsdata/qemu_9.0.0.x86_64.xml
+++ b/tests/domaincapsdata/qemu_9.0.0.x86_64.xml
@@ -290,6 +290,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml b/tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml
index 5ca6d0fdac..c9bf0139b5 100644
--- a/tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml
+++ b/tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml
@@ -294,6 +294,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml b/tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml
index 133ee4d723..288047b38b 100644
--- a/tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml
+++ b/tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml
@@ -290,6 +290,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/domaincapsdata/qemu_9.1.0.x86_64.xml b/tests/domaincapsdata/qemu_9.1.0.x86_64.xml
index f378000c2b..4cae2f73cc 100644
--- a/tests/domaincapsdata/qemu_9.1.0.x86_64.xml
+++ b/tests/domaincapsdata/qemu_9.1.0.x86_64.xml
@@ -294,6 +294,7 @@
         <value>tlbflush</value>
         <value>ipi</value>
         <value>avic</value>
+        <value>emsr_bitmap</value>
       </enum>
     </hyperv>
     <launchSecurity supported='no'/>
diff --git a/tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml b/tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml
index d3901fef05..2c9c2ebbbb 100644
--- a/tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml
@@ -3455,5 +3455,6 @@
     <cap name='tlbflush'/>
     <cap name='ipi'/>
     <cap name='avic'/>
+    <cap name='emsr_bitmap'/>
   </hypervCapabilities>
 </qemuCaps>
diff --git a/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml b/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml
index f8a9993ede..6a87c1d9cc 100644
--- a/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml
@@ -3784,5 +3784,6 @@
     <cap name='tlbflush'/>
     <cap name='ipi'/>
     <cap name='avic'/>
+    <cap name='emsr_bitmap'/>
   </hypervCapabilities>
 </qemuCaps>
diff --git a/tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml b/tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml
index 43d7105c2d..6713905b2f 100644
--- a/tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml
@@ -3758,5 +3758,6 @@
     <cap name='tlbflush'/>
     <cap name='ipi'/>
     <cap name='avic'/>
+    <cap name='emsr_bitmap'/>
   </hypervCapabilities>
 </qemuCaps>
diff --git a/tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml b/tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml
index e96af86a92..520a2f95ee 100644
--- a/tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml
@@ -3693,5 +3693,6 @@
     <cap name='tlbflush'/>
     <cap name='ipi'/>
     <cap name='avic'/>
+    <cap name='emsr_bitmap'/>
   </hypervCapabilities>
 </qemuCaps>
diff --git a/tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml b/tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml
index c3cb6efc61..f5db55dc86 100644
--- a/tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml
+++ b/tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml
@@ -3949,5 +3949,6 @@
     <cap name='tlbflush'/>
     <cap name='ipi'/>
     <cap name='avic'/>
+    <cap name='emsr_bitmap'/>
   </hypervCapabilities>
 </qemuCaps>
diff --git a/tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml b/tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml
index 5805fea7b7..2b5f3537a8 100644
--- a/tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml
+++ b/tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml
@@ -25,6 +25,7 @@
       <tlbflush state='off'/>
       <ipi state='off'/>
       <evmcs state='off'/>
+      <emsr_bitmap state='off'/>
     </hyperv>
   </features>
   <cpu mode='custom' match='exact' check='none'>
diff --git a/tests/qemuxmlconfdata/hyperv-off.xml b/tests/qemuxmlconfdata/hyperv-off.xml
index 1e7e632b1c..f760a9676b 100644
--- a/tests/qemuxmlconfdata/hyperv-off.xml
+++ b/tests/qemuxmlconfdata/hyperv-off.xml
@@ -25,6 +25,7 @@
       <tlbflush state='off'/>
       <ipi state='off'/>
       <evmcs state='off'/>
+      <emsr_bitmap state='off'/>
     </hyperv>
   </features>
   <clock offset='utc'/>
diff --git a/tests/qemuxmlconfdata/hyperv.x86_64-latest.args b/tests/qemuxmlconfdata/hyperv.x86_64-latest.args
index 8f0a02230c..5046ec6ea0 100644
--- a/tests/qemuxmlconfdata/hyperv.x86_64-latest.args
+++ b/tests/qemuxmlconfdata/hyperv.x86_64-latest.args
@@ -12,7 +12,7 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
 -object '{"qom-type":"secret","id":"masterKey0","format":"raw","file":"/var/lib/libvirt/qemu/domain--1-QEMUGuest1/master-key.aes"}' \
 -machine pc,usb=off,dump-guest-core=off,memory-backend=pc.ram,acpi=on \
 -accel tcg \
--cpu 'qemu64,hv-relaxed=on,hv-vapic=on,hv-spinlocks=0x2fff,hv-vpindex=on,hv-runtime=on,hv-synic=on,hv-stimer=on,hv-reset=on,hv-vendor-id=KVM Hv,hv-frequencies=on,hv-reenlightenment=on,hv-tlbflush=on,hv-ipi=on,hv-evmcs=on,hv-avic=on' \
+-cpu 'qemu64,hv-relaxed=on,hv-vapic=on,hv-spinlocks=0x2fff,hv-vpindex=on,hv-runtime=on,hv-synic=on,hv-stimer=on,hv-reset=on,hv-vendor-id=KVM Hv,hv-frequencies=on,hv-reenlightenment=on,hv-tlbflush=on,hv-ipi=on,hv-evmcs=on,hv-avic=on,hv-emsr-bitmap=on' \
 -m size=219136k \
 -object '{"qom-type":"memory-backend-ram","id":"pc.ram","size":224395264}' \
 -overcommit mem-lock=off \
diff --git a/tests/qemuxmlconfdata/hyperv.x86_64-latest.xml b/tests/qemuxmlconfdata/hyperv.x86_64-latest.xml
index 4828177263..d5cb27bf1d 100644
--- a/tests/qemuxmlconfdata/hyperv.x86_64-latest.xml
+++ b/tests/qemuxmlconfdata/hyperv.x86_64-latest.xml
@@ -26,6 +26,7 @@
       <ipi state='on'/>
       <evmcs state='on'/>
       <avic state='on'/>
+      <emsr_bitmap state='on'/>
     </hyperv>
   </features>
   <cpu mode='custom' match='exact' check='none'>
diff --git a/tests/qemuxmlconfdata/hyperv.xml b/tests/qemuxmlconfdata/hyperv.xml
index dde091aa9a..db520e2074 100644
--- a/tests/qemuxmlconfdata/hyperv.xml
+++ b/tests/qemuxmlconfdata/hyperv.xml
@@ -26,6 +26,7 @@
       <ipi state='on'/>
       <evmcs state='on'/>
       <avic state='on'/>
+      <emsr_bitmap state='on'/>
     </hyperv>
   </features>
   <clock offset='utc'/>
-- 
2.43.0
Re: [PATCH 1/2] hyperv: Support hv-emsr-bitmap enlightenment
Posted by Martin Kletzander 3 months ago 
On Thu, Aug 15, 2024 at 03:57:35PM +0200, Tim Wiederhake wrote:
>qemu supports this enlightenment since version 7.10.
>
>From the qemu commit:
>    The newly introduced enlightenment allow L0 (KVM) and L1 (Hyper-V)
>    hypervisors to collaborate to avoid unnecessary updates to L2
>    MSR-Bitmap upon vmexits.
>
>Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
>---
> docs/formatdomain.rst                              | 2 ++
> src/conf/domain_conf.c                             | 4 ++++
> src/conf/domain_conf.h                             | 1 +
> src/conf/schemas/domaincommon.rng                  | 5 +++++
> src/cpu/cpu_x86.c                                  | 4 ++++
> src/cpu/cpu_x86_data.h                             | 1 +
> src/qemu/qemu_command.c                            | 5 +++++
> src/qemu/qemu_process.c                            | 1 +
> tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_8.0.0.x86_64.xml         | 1 +
> tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_8.1.0.x86_64.xml         | 1 +
> tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_8.2.0.x86_64.xml         | 1 +
> tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_9.0.0.x86_64.xml         | 1 +
> tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml     | 1 +
> tests/domaincapsdata/qemu_9.1.0.x86_64.xml         | 1 +
> tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml   | 1 +
> tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml   | 1 +
> tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml   | 1 +
> tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml   | 1 +
> tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml   | 1 +
> tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml | 1 +
> tests/qemuxmlconfdata/hyperv-off.xml               | 1 +
> tests/qemuxmlconfdata/hyperv.x86_64-latest.args    | 2 +-
> tests/qemuxmlconfdata/hyperv.x86_64-latest.xml     | 1 +
> tests/qemuxmlconfdata/hyperv.xml                   | 1 +
> 33 files changed, 48 insertions(+), 1 deletion(-)
>
>diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
>index e1e219bcb5..0cf3dc9deb 100644
>--- a/docs/formatdomain.rst
>+++ b/docs/formatdomain.rst
>@@ -1989,6 +1989,7 @@ Hypervisors may allow certain CPU / machine features to be toggled on/off.
>        <tlbflush state='on'/>
>        <ipi state='on'/>
>        <evmcs state='on'/>
>+       <emsr_bitmap state='on'/>
>      </hyperv>
>      <kvm>
>        <hidden state='on'/>
>@@ -2076,6 +2077,7 @@ are:
>    ipi             Enable PV IPI support                                                  on, off                                      :since:`4.10.0 (QEMU 3.1)`
>    evmcs           Enable Enlightened VMCS                                                on, off                                      :since:`4.10.0 (QEMU 3.1)`
>    avic            Enable use Hyper-V SynIC with hardware APICv/AVIC                      on, off                                      :since:`8.10.0 (QEMU 6.2)`
>+   emsr_bitmap     Avoid unnecessary updates to L2 MSR Bitmap upon vmexits.               on, off                                      :since:`10.7.0 (QEMU 7.1)`
>    =============== ====================================================================== ============================================ =======================================================
>
>    :since:`Since 8.0.0`, the hypervisor can be configured further by setting
>diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>index d950921667..c88e885d07 100644
>--- a/src/conf/domain_conf.c
>+++ b/src/conf/domain_conf.c
>@@ -211,6 +211,7 @@ VIR_ENUM_IMPL(virDomainHyperv,
>               "ipi",
>               "evmcs",
>               "avic",
>+              "emsr_bitmap",
> );
>
> VIR_ENUM_IMPL(virDomainKVM,
>@@ -16574,6 +16575,7 @@ virDomainFeaturesHyperVDefParse(virDomainDef *def,
>         case VIR_DOMAIN_HYPERV_IPI:
>         case VIR_DOMAIN_HYPERV_EVMCS:
>         case VIR_DOMAIN_HYPERV_AVIC:
>+        case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
>             break;
>
>         case VIR_DOMAIN_HYPERV_STIMER:
>@@ -21020,6 +21022,7 @@ virDomainDefFeaturesCheckABIStability(virDomainDef *src,
>             case VIR_DOMAIN_HYPERV_IPI:
>             case VIR_DOMAIN_HYPERV_EVMCS:
>             case VIR_DOMAIN_HYPERV_AVIC:
>+            case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
>                 if (src->hyperv_features[i] != dst->hyperv_features[i]) {
>                     virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>                                    _("State of HyperV enlightenment feature '%1$s' differs: source: '%2$s', destination: '%3$s'"),
>@@ -27761,6 +27764,7 @@ virDomainDefFormatFeatures(virBuffer *buf,
>                 case VIR_DOMAIN_HYPERV_IPI:
>                 case VIR_DOMAIN_HYPERV_EVMCS:
>                 case VIR_DOMAIN_HYPERV_AVIC:
>+                case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
>                     virBufferAddLit(&childBuf, "/>\n");
>                     break;
>
>diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
>index eae621f900..332bcd0cf9 100644
>--- a/src/conf/domain_conf.h
>+++ b/src/conf/domain_conf.h
>@@ -2203,6 +2203,7 @@ typedef enum {
>     VIR_DOMAIN_HYPERV_IPI,
>     VIR_DOMAIN_HYPERV_EVMCS,
>     VIR_DOMAIN_HYPERV_AVIC,
>+    VIR_DOMAIN_HYPERV_EMSR_BITMAP,
>
>     VIR_DOMAIN_HYPERV_LAST
> } virDomainHyperv;
>diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
>index 05ba697924..6f81fc94c2 100644
>--- a/src/conf/schemas/domaincommon.rng
>+++ b/src/conf/schemas/domaincommon.rng
>@@ -7962,6 +7962,11 @@
>                 <ref name="featurestate"/>
>               </element>
>             </optional>
>+            <optional>
>+              <element name="emsr_bitmap">
>+                <ref name="featurestate"/>
>+              </element>
>+            </optional>
>           </interleave>
>         </group>
>       </choice>
>diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
>index fcbce0ec46..139ac48234 100644
>--- a/src/cpu/cpu_x86.c
>+++ b/src/cpu/cpu_x86.c
>@@ -107,6 +107,9 @@ KVM_FEATURE_DEF(VIR_CPU_x86_HV_IPI,
> KVM_FEATURE_DEF(VIR_CPU_x86_HV_EVMCS,
>                 0x40000004, 0x00004000, 0x0);
>
>+KVM_FEATURE_DEF(VIR_CPU_x86_HV_EMSR_BITMAP,
>+                0x4000000A, 0x00080000, 0x0);
>+
> static virCPUx86Feature x86_kvm_features[] =
> {
>     KVM_FEATURE(VIR_CPU_x86_KVM_PV_UNHALT),
>@@ -124,6 +127,7 @@ static virCPUx86Feature x86_kvm_features[] =
>     KVM_FEATURE(VIR_CPU_x86_HV_IPI),
>     KVM_FEATURE(VIR_CPU_x86_HV_EVMCS),
>     KVM_FEATURE(VIR_CPU_x86_HV_STIMER_DIRECT),
>+    KVM_FEATURE(VIR_CPU_x86_HV_EMSR_BITMAP),
> };
>
> typedef struct _virCPUx86Signature virCPUx86Signature;
>diff --git a/src/cpu/cpu_x86_data.h b/src/cpu/cpu_x86_data.h
>index d1ca63db6d..414643fe8d 100644
>--- a/src/cpu/cpu_x86_data.h
>+++ b/src/cpu/cpu_x86_data.h
>@@ -62,6 +62,7 @@ struct _virCPUx86MSR {
> #define VIR_CPU_x86_HV_IPI       "hv-ipi"
> #define VIR_CPU_x86_HV_EVMCS     "hv-evmcs"
> #define VIR_CPU_x86_HV_AVIC      "hv-avic"
>+#define VIR_CPU_x86_HV_EMSR_BITMAP "hv-emsr_bitmap"
>
> /* Hyper-V Synthetic Timer option */
> #define VIR_CPU_x86_HV_STIMER_DIRECT "hv-stimer-direct"
>diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
>index 28914c9c34..cac6fc57a5 100644
>--- a/src/qemu/qemu_command.c
>+++ b/src/qemu/qemu_command.c
>@@ -6523,6 +6523,11 @@ qemuBuildCpuCommandLine(virCommand *cmd,
>                                       def->hyperv_vendor_id);
>                 break;
>
>+            case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
>+                if (def->hyperv_features[i] == VIR_TRISTATE_SWITCH_ON)
>+                    virBufferAsprintf(&buf, ",%s=on", "hv-emsr-bitmap");
>+                break;
>+

What is the reason for us to only include the "on" state?  Is it because
qemu guarantees the default is (and always will be) off?  If that is
true, then

Reviewed-by: Martin Kletzander <mkletzan@redhat.com>

If not, then we should adapt this and all of the above to something like:

if (def->hyperv_features[i] == VIR_TRISTATE_SWITCH_ABSENT) {
     virBufferAsprintf(&buf,
                       ",%s=%s",
                       "hv-emsr-bitmap",
                       virTristateSwitchTypeToString(def->hyperv_features[i]));
}

or no?
Re: [PATCH 1/2] hyperv: Support hv-emsr-bitmap enlightenment
Posted by Tim Wiederhake 2 months, 4 weeks ago 
On Wed, 2024-08-21 at 12:19 +0200, Martin Kletzander wrote:
> On Thu, Aug 15, 2024 at 03:57:35PM +0200, Tim Wiederhake wrote:
> > qemu supports this enlightenment since version 7.10.
> > 
> > From the qemu commit:
> >    The newly introduced enlightenment allow L0 (KVM) and L1 (Hyper-
> > V)
> >    hypervisors to collaborate to avoid unnecessary updates to L2
> >    MSR-Bitmap upon vmexits.
> > 
> > Signed-off-by: Tim Wiederhake <twiederh@redhat.com>
> > ---
> > docs/formatdomain.rst                              | 2 ++
> > src/conf/domain_conf.c                             | 4 ++++
> > src/conf/domain_conf.h                             | 1 +
> > src/conf/schemas/domaincommon.rng                  | 5 +++++
> > src/cpu/cpu_x86.c                                  | 4 ++++
> > src/cpu/cpu_x86_data.h                             | 1 +
> > src/qemu/qemu_command.c                            | 5 +++++
> > src/qemu/qemu_process.c                            | 1 +
> > tests/domaincapsdata/qemu_8.0.0-q35.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_8.0.0-tcg.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_8.0.0.x86_64.xml         | 1 +
> > tests/domaincapsdata/qemu_8.1.0-q35.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_8.1.0-tcg.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_8.1.0.x86_64.xml         | 1 +
> > tests/domaincapsdata/qemu_8.2.0-q35.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_8.2.0-tcg.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_8.2.0.x86_64.xml         | 1 +
> > tests/domaincapsdata/qemu_9.0.0-q35.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_9.0.0-tcg.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_9.0.0.x86_64.xml         | 1 +
> > tests/domaincapsdata/qemu_9.1.0-q35.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_9.1.0-tcg.x86_64.xml     | 1 +
> > tests/domaincapsdata/qemu_9.1.0.x86_64.xml         | 1 +
> > tests/qemucapabilitiesdata/caps_8.0.0_x86_64.xml   | 1 +
> > tests/qemucapabilitiesdata/caps_8.1.0_x86_64.xml   | 1 +
> > tests/qemucapabilitiesdata/caps_8.2.0_x86_64.xml   | 1 +
> > tests/qemucapabilitiesdata/caps_9.0.0_x86_64.xml   | 1 +
> > tests/qemucapabilitiesdata/caps_9.1.0_x86_64.xml   | 1 +
> > tests/qemuxmlconfdata/hyperv-off.x86_64-latest.xml | 1 +
> > tests/qemuxmlconfdata/hyperv-off.xml               | 1 +
> > tests/qemuxmlconfdata/hyperv.x86_64-latest.args    | 2 +-
> > tests/qemuxmlconfdata/hyperv.x86_64-latest.xml     | 1 +
> > tests/qemuxmlconfdata/hyperv.xml                   | 1 +
> > 33 files changed, 48 insertions(+), 1 deletion(-)
> > 
> > diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
> > index e1e219bcb5..0cf3dc9deb 100644
> > --- a/docs/formatdomain.rst
> > +++ b/docs/formatdomain.rst
> > @@ -1989,6 +1989,7 @@ Hypervisors may allow certain CPU / machine
> > features to be toggled on/off.
> >        <tlbflush state='on'/>
> >        <ipi state='on'/>
> >        <evmcs state='on'/>
> > +       <emsr_bitmap state='on'/>
> >      </hyperv>
> >      <kvm>
> >        <hidden state='on'/>
> > @@ -2076,6 +2077,7 @@ are:
> >    ipi             Enable PV IPI
> > support                                                  on,
> > off                                      :since:`4.10.0 (QEMU 3.1)`
> >    evmcs           Enable Enlightened
> > VMCS                                                on,
> > off                                      :since:`4.10.0 (QEMU 3.1)`
> >    avic            Enable use Hyper-V SynIC with hardware
> > APICv/AVIC                      on,
> > off                                      :since:`8.10.0 (QEMU 6.2)`
> > +   emsr_bitmap     Avoid unnecessary updates to L2 MSR Bitmap upon
> > vmexits.               on, off                                     
> > :since:`10.7.0 (QEMU 7.1)`
> >    ===============
> > ===================================================================
> > === ============================================
> > =======================================================
> > 
> >    :since:`Since 8.0.0`, the hypervisor can be configured further
> > by setting
> > diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> > index d950921667..c88e885d07 100644
> > --- a/src/conf/domain_conf.c
> > +++ b/src/conf/domain_conf.c
> > @@ -211,6 +211,7 @@ VIR_ENUM_IMPL(virDomainHyperv,
> >               "ipi",
> >               "evmcs",
> >               "avic",
> > +              "emsr_bitmap",
> > );
> > 
> > VIR_ENUM_IMPL(virDomainKVM,
> > @@ -16574,6 +16575,7 @@
> > virDomainFeaturesHyperVDefParse(virDomainDef *def,
> >         case VIR_DOMAIN_HYPERV_IPI:
> >         case VIR_DOMAIN_HYPERV_EVMCS:
> >         case VIR_DOMAIN_HYPERV_AVIC:
> > +        case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
> >             break;
> > 
> >         case VIR_DOMAIN_HYPERV_STIMER:
> > @@ -21020,6 +21022,7 @@
> > virDomainDefFeaturesCheckABIStability(virDomainDef *src,
> >             case VIR_DOMAIN_HYPERV_IPI:
> >             case VIR_DOMAIN_HYPERV_EVMCS:
> >             case VIR_DOMAIN_HYPERV_AVIC:
> > +            case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
> >                 if (src->hyperv_features[i] != dst-
> > >hyperv_features[i]) {
> >                     virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> >                                    _("State of HyperV enlightenment
> > feature '%1$s' differs: source: '%2$s', destination: '%3$s'"),
> > @@ -27761,6 +27764,7 @@ virDomainDefFormatFeatures(virBuffer *buf,
> >                 case VIR_DOMAIN_HYPERV_IPI:
> >                 case VIR_DOMAIN_HYPERV_EVMCS:
> >                 case VIR_DOMAIN_HYPERV_AVIC:
> > +                case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
> >                     virBufferAddLit(&childBuf, "/>\n");
> >                     break;
> > 
> > diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> > index eae621f900..332bcd0cf9 100644
> > --- a/src/conf/domain_conf.h
> > +++ b/src/conf/domain_conf.h
> > @@ -2203,6 +2203,7 @@ typedef enum {
> >     VIR_DOMAIN_HYPERV_IPI,
> >     VIR_DOMAIN_HYPERV_EVMCS,
> >     VIR_DOMAIN_HYPERV_AVIC,
> > +    VIR_DOMAIN_HYPERV_EMSR_BITMAP,
> > 
> >     VIR_DOMAIN_HYPERV_LAST
> > } virDomainHyperv;
> > diff --git a/src/conf/schemas/domaincommon.rng
> > b/src/conf/schemas/domaincommon.rng
> > index 05ba697924..6f81fc94c2 100644
> > --- a/src/conf/schemas/domaincommon.rng
> > +++ b/src/conf/schemas/domaincommon.rng
> > @@ -7962,6 +7962,11 @@
> >                 <ref name="featurestate"/>
> >               </element>
> >             </optional>
> > +            <optional>
> > +              <element name="emsr_bitmap">
> > +                <ref name="featurestate"/>
> > +              </element>
> > +            </optional>
> >           </interleave>
> >         </group>
> >       </choice>
> > diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
> > index fcbce0ec46..139ac48234 100644
> > --- a/src/cpu/cpu_x86.c
> > +++ b/src/cpu/cpu_x86.c
> > @@ -107,6 +107,9 @@ KVM_FEATURE_DEF(VIR_CPU_x86_HV_IPI,
> > KVM_FEATURE_DEF(VIR_CPU_x86_HV_EVMCS,
> >                 0x40000004, 0x00004000, 0x0);
> > 
> > +KVM_FEATURE_DEF(VIR_CPU_x86_HV_EMSR_BITMAP,
> > +                0x4000000A, 0x00080000, 0x0);
> > +
> > static virCPUx86Feature x86_kvm_features[] =
> > {
> >     KVM_FEATURE(VIR_CPU_x86_KVM_PV_UNHALT),
> > @@ -124,6 +127,7 @@ static virCPUx86Feature x86_kvm_features[] =
> >     KVM_FEATURE(VIR_CPU_x86_HV_IPI),
> >     KVM_FEATURE(VIR_CPU_x86_HV_EVMCS),
> >     KVM_FEATURE(VIR_CPU_x86_HV_STIMER_DIRECT),
> > +    KVM_FEATURE(VIR_CPU_x86_HV_EMSR_BITMAP),
> > };
> > 
> > typedef struct _virCPUx86Signature virCPUx86Signature;
> > diff --git a/src/cpu/cpu_x86_data.h b/src/cpu/cpu_x86_data.h
> > index d1ca63db6d..414643fe8d 100644
> > --- a/src/cpu/cpu_x86_data.h
> > +++ b/src/cpu/cpu_x86_data.h
> > @@ -62,6 +62,7 @@ struct _virCPUx86MSR {
> > #define VIR_CPU_x86_HV_IPI       "hv-ipi"
> > #define VIR_CPU_x86_HV_EVMCS     "hv-evmcs"
> > #define VIR_CPU_x86_HV_AVIC      "hv-avic"
> > +#define VIR_CPU_x86_HV_EMSR_BITMAP "hv-emsr_bitmap"
> > 
> > /* Hyper-V Synthetic Timer option */
> > #define VIR_CPU_x86_HV_STIMER_DIRECT "hv-stimer-direct"
> > diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> > index 28914c9c34..cac6fc57a5 100644
> > --- a/src/qemu/qemu_command.c
> > +++ b/src/qemu/qemu_command.c
> > @@ -6523,6 +6523,11 @@ qemuBuildCpuCommandLine(virCommand *cmd,
> >                                       def->hyperv_vendor_id);
> >                 break;
> > 
> > +            case VIR_DOMAIN_HYPERV_EMSR_BITMAP:
> > +                if (def->hyperv_features[i] ==
> > VIR_TRISTATE_SWITCH_ON)
> > +                    virBufferAsprintf(&buf, ",%s=on", "hv-emsr-
> > bitmap");
> > +                break;
> > +
> 
> What is the reason for us to only include the "on" state?  Is it
> because
> qemu guarantees the default is (and always will be) off?  If that is
> true, then
> 
> Reviewed-by: Martin Kletzander <mkletzan@redhat.com>
> 
From https://www.qemu.org/docs/master/system/i386/hyperv.html:

    No Hyper-V enlightenments are enabled by default by either KVM or
    QEMU. In QEMU, individual enlightenments can be enabled through
    CPU flags (...)"

> If not, then we should adapt this and all of the above to something
> like:
> 
> if (def->hyperv_features[i] == VIR_TRISTATE_SWITCH_ABSENT) {
>      virBufferAsprintf(&buf,
>                        ",%s=%s",
>                        "hv-emsr-bitmap",
>                        virTristateSwitchTypeToString(def-
> >hyperv_features[i]));
> }
> 
> or no?

Patchew 2.1-devel-b67e4c2

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