[PATCH v3 4/5] qemu: add support for Direct Mode for Hyper-V Synthetic timers

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

QEMU-4.1 supports 'Direct Mode' for Hyper-V synthetic timers
(hv-stimer-direct CPU flag): Windows guests can request that timer
expiration notifications are delivered as normal interrupts (and not
VMBus messages). This is used by Hyper-V on KVM.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 src/qemu/qemu_command.c             | 12 ++++++++----
 src/qemu/qemu_process.c             | 20 ++++++++++++++++++--
 tests/qemuxml2argvdata/hyperv.args  |  4 ++--
 tests/qemuxml2argvdata/hyperv.xml   |  4 +++-
 tests/qemuxml2xmloutdata/hyperv.xml |  4 +++-
 5 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index c8494de785..af913dba34 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -7152,10 +7152,10 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
     }
 
     if (def->features[VIR_DOMAIN_FEATURE_HYPERV] == VIR_TRISTATE_SWITCH_ON) {
-        const char *hvPrefix = "hv-";
+        const char *hvDelimiter = "-";
 
         if (!virQEMUCapsGet(qemuCaps, QEMU_CAPS_CANONICAL_CPU_FEATURES))
-            hvPrefix = "hv_";
+            hvDelimiter = "_";
 
         for (i = 0; i < VIR_DOMAIN_HYPERV_LAST; i++) {
             switch ((virDomainHyperv) i) {
@@ -7172,9 +7172,13 @@ qemuBuildCpuCommandLine(virCommandPtr cmd,
             case VIR_DOMAIN_HYPERV_IPI:
             case VIR_DOMAIN_HYPERV_EVMCS:
                 if (def->hyperv_features[i] == VIR_TRISTATE_SWITCH_ON)
-                    virBufferAsprintf(&buf, ",%s%s",
-                                      hvPrefix,
+                    virBufferAsprintf(&buf, ",hv%s%s",
+                                      hvDelimiter,
                                       virDomainHypervTypeToString(i));
+                if ((i == VIR_DOMAIN_HYPERV_STIMER) &&
+                    (def->hyperv_stimer_direct == VIR_TRISTATE_SWITCH_ON))
+                    virBufferAsprintf(&buf, ",hv%sstimer%sdirect", hvDelimiter,
+                                      hvDelimiter);
                 break;
 
             case VIR_DOMAIN_HYPERV_SPINLOCKS:
diff --git a/src/qemu/qemu_process.c b/src/qemu/qemu_process.c
index 1ed56457b1..792fa33327 100644
--- a/src/qemu/qemu_process.c
+++ b/src/qemu/qemu_process.c
@@ -4112,10 +4112,26 @@ qemuProcessVerifyHypervFeatures(virDomainDefPtr def,
         rc = virCPUDataCheckFeature(cpu, cpuFeature);
         VIR_FREE(cpuFeature);
 
-        if (rc < 0)
+        if (rc < 0) {
             return -1;
-        else if (rc == 1)
+        } else if (rc == 1) {
+            if (i == VIR_DOMAIN_HYPERV_STIMER) {
+                if (def->hyperv_stimer_direct != VIR_TRISTATE_SWITCH_ON)
+                    continue;
+
+                rc = virCPUDataCheckFeature(cpu, "hv-stimer-direct");
+                if (rc < 0)
+                    return -1;
+                else if (rc == 1)
+                    continue;
+
+                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                               _("host doesn't support hyperv stimer '%s' feature"),
+                               "direct");
+                return -1;
+            }
             continue;
+        }
 
         switch ((virDomainHyperv) i) {
         case VIR_DOMAIN_HYPERV_RELAXED:
diff --git a/tests/qemuxml2argvdata/hyperv.args b/tests/qemuxml2argvdata/hyperv.args
index 086adaa349..8040da9caa 100644
--- a/tests/qemuxml2argvdata/hyperv.args
+++ b/tests/qemuxml2argvdata/hyperv.args
@@ -12,8 +12,8 @@ QEMU_AUDIO_DRV=none \
 -S \
 -machine pc,accel=tcg,usb=off,dump-guest-core=off \
 -cpu 'qemu32,hv_relaxed,hv_vapic,hv-spinlocks=0x2fff,hv_vpindex,hv_runtime,\
-hv_synic,hv_stimer,hv_reset,hv-vendor-id=KVM Hv,hv_frequencies,\
-hv_reenlightenment,hv_tlbflush,hv_ipi,hv_evmcs' \
+hv_synic,hv_stimer,hv_stimer_direct,hv_reset,hv-vendor-id=KVM Hv,\
+hv_frequencies,hv_reenlightenment,hv_tlbflush,hv_ipi,hv_evmcs' \
 -m 214 \
 -realtime mlock=off \
 -smp 6,sockets=6,cores=1,threads=1 \
diff --git a/tests/qemuxml2argvdata/hyperv.xml b/tests/qemuxml2argvdata/hyperv.xml
index c6feaed528..ae0f934f76 100644
--- a/tests/qemuxml2argvdata/hyperv.xml
+++ b/tests/qemuxml2argvdata/hyperv.xml
@@ -17,7 +17,9 @@
       <vpindex state='on'/>
       <runtime state='on'/>
       <synic state='on'/>
-      <stimer state='on'/>
+      <stimer state='on'>
+        <direct state='on'/>
+      </stimer>
       <reset state='on'/>
       <vendor_id state='on' value='KVM Hv'/>
       <frequencies state='on'/>
diff --git a/tests/qemuxml2xmloutdata/hyperv.xml b/tests/qemuxml2xmloutdata/hyperv.xml
index 5510d3dfad..2e4b43d4c6 100644
--- a/tests/qemuxml2xmloutdata/hyperv.xml
+++ b/tests/qemuxml2xmloutdata/hyperv.xml
@@ -17,7 +17,9 @@
       <vpindex state='on'/>
       <runtime state='on'/>
       <synic state='on'/>
-      <stimer state='on'/>
+      <stimer state='on'>
+        <direct state='on'/>
+      </stimer>
       <reset state='on'/>
       <vendor_id state='on' value='KVM Hv'/>
       <frequencies state='on'/>
-- 
2.20.1

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