[Qemu-devel] [PATCH 8/8] i386/kvm: add support for Direct Mode for Hyper-V synthetic timers

[Vitaly Kuznetsov]

Hyper-V on KVM can only use Synthetic timers with Direct Mode (opting for
an interrupt instead of VMBus message). This new capability is only
announced in KVM_GET_SUPPORTED_HV_CPUID.

Signed-off-by: Vitaly Kuznetsov <address@hidden>
---
 docs/hyperv.txt            | 10 ++++++++++
 target/i386/cpu.c          |  1 +
 target/i386/cpu.h          |  1 +
 target/i386/hyperv-proto.h |  1 +
 target/i386/kvm.c          | 15 +++++++++++++++
 5 files changed, 28 insertions(+)

diff --git a/docs/hyperv.txt b/docs/hyperv.txt
index d1299aba81..e1988ab648 100644
--- a/docs/hyperv.txt
+++ b/docs/hyperv.txt
@@ -173,6 +173,16 @@ without the feature to find out if enabling it is 
beneficial.
 
 Requires: hv-vapic
 
+3.17. hv-stimer-direct
+=======================
+Hyper-V specification allows synthetic timer operation in two modes: "classic",
+when expiration event is delivered as SynIC message and "direct", when the 
event
+is delivered via normal interrupt. It is known that nested Hyper-V can only
+use synthetic timers in direct mode and thus 'hv-stimer-direct' needs to be
+enabled.
+
+Requires: hv-vpindex, hv-synic, hv-time, hv-stimer
+
 
 4. Development features
 ========================
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 4e01ad076e..ea3843ed0c 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -5785,6 +5785,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_BOOL("hv-tlbflush", X86CPU, hyperv_tlbflush, false),
     DEFINE_PROP_BOOL("hv-evmcs", X86CPU, hyperv_evmcs, false),
     DEFINE_PROP_BOOL("hv-ipi", X86CPU, hyperv_ipi, false),
+    DEFINE_PROP_BOOL("hv-stimer-direct", X86CPU, hyperv_stimer_direct, false),
     DEFINE_PROP_BOOL("hv-all", X86CPU, hyperv_all, false),
     DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
     DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 9cd3a8bc2f..3f1ada3e39 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1396,6 +1396,7 @@ struct X86CPU {
     bool hyperv_tlbflush;
     bool hyperv_evmcs;
     bool hyperv_ipi;
+    bool hyperv_stimer_direct;
     bool hyperv_all;
     bool check_cpuid;
     bool enforce_cpuid;
diff --git a/target/i386/hyperv-proto.h b/target/i386/hyperv-proto.h
index c0272b3a01..cffac10b45 100644
--- a/target/i386/hyperv-proto.h
+++ b/target/i386/hyperv-proto.h
@@ -49,6 +49,7 @@
 #define HV_GUEST_IDLE_STATE_AVAILABLE           (1u << 5)
 #define HV_FREQUENCY_MSRS_AVAILABLE             (1u << 8)
 #define HV_GUEST_CRASH_MSR_AVAILABLE            (1u << 10)
+#define HV_STIMER_DIRECT_MODE_AVAILABLE         (1u << 19)
 
 /*
  * HV_CPUID_ENLIGHTMENT_INFO.EAX bits
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 976c1d570f..f3c73b7c4e 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -657,6 +657,7 @@ static bool hyperv_enabled(X86CPU *cpu)
             cpu->hyperv_reenlightenment ||
             cpu->hyperv_tlbflush ||
             cpu->hyperv_ipi ||
+            cpu->hyperv_stimer_direct ||
             cpu->hyperv_all);
 }
 
@@ -832,6 +833,15 @@ static struct {
             {0}
         }
     },
+    {
+        .name = "hv-stimer-direct",
+        .desc = "direct mode timers",
+        .flags = {
+            {.fw = FEAT_HYPERV_EDX,
+             .bits = HV_STIMER_DIRECT_MODE_AVAILABLE},
+            {0}
+        }
+    },
 };
 
 static struct kvm_cpuid2 *try_get_hv_cpuid(CPUState *cs, int max)
@@ -1178,6 +1188,8 @@ static int hyperv_handle_properties(CPUState *cs,
     r |= hv_cpuid_check_and_set(cs, cpuid, "hv-tlbflush",
                                 &cpu->hyperv_tlbflush);
     r |= hv_cpuid_check_and_set(cs, cpuid, "hv-ipi", &cpu->hyperv_ipi);
+    r |= hv_cpuid_check_and_set(cs, cpuid, "hv-stimer-direct",
+                                &cpu->hyperv_stimer_direct);
 
     /* Dependencies */
     if (cpu->hyperv_synic && !cpu->hyperv_synic_kvm_only &&
@@ -1198,6 +1210,9 @@ static int hyperv_handle_properties(CPUState *cs,
     if (cpu->hyperv_ipi && !cpu->hyperv_vpindex) {
         r |= hv_report_missing_dep(cpu, "hv-ipi", "hv-vpindex");
     }
+    if (cpu->hyperv_stimer_direct && !cpu->hyperv_stimer) {
+        r |= hv_report_missing_dep(cpu, "hv-stimer-direct", "hv-stimer");
+    }
 
     /* Not exposed by KVM but needed to make CPU hotplug in Windows work */
     env->features[FEAT_HYPERV_EDX] |= HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE;
-- 
2.20.1