[Qemu-devel] [PATCH 1/2] i386/kvm: add support for Hyper-V reenlightenment MSRs

[Vitaly Kuznetsov <vkuznets@redhat.com>]

KVM recently gained support for Hyper-V Reenlightenment MSRs which are
required to make KVM-on-Hyper-V enable TSC page clocksource to its guests
when INVTSC is not passed to it (and it is not passed by default in Qemu
as it effectively blocks migration).

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 target/i386/cpu.h          |  3 +++
 target/i386/hyperv-proto.h |  9 ++++++++-
 target/i386/kvm.c          | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index faf39ec1ce..502b535be2 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1152,6 +1152,9 @@ typedef struct CPUX86State {
     uint64_t msr_hv_synic_sint[HV_SINT_COUNT];
     uint64_t msr_hv_stimer_config[HV_STIMER_COUNT];
     uint64_t msr_hv_stimer_count[HV_STIMER_COUNT];
+    uint64_t msr_hv_reenlightenment_control;
+    uint64_t msr_hv_tsc_emulation_control;
+    uint64_t msr_hv_tsc_emulation_status;
 
     /* exception/interrupt handling */
     int error_code;
diff --git a/target/i386/hyperv-proto.h b/target/i386/hyperv-proto.h
index cb4d7f2b7a..93352ebd2a 100644
--- a/target/i386/hyperv-proto.h
+++ b/target/i386/hyperv-proto.h
@@ -35,7 +35,7 @@
 #define HV_RESET_AVAILABLE           (1u << 7)
 #define HV_REFERENCE_TSC_AVAILABLE   (1u << 9)
 #define HV_ACCESS_FREQUENCY_MSRS     (1u << 11)
-
+#define HV_ACCESS_REENLIGHTENMENTS_CONTROL  (1u << 13)
 
 /*
  * HV_CPUID_FEATURES.EDX bits
@@ -129,6 +129,13 @@
 #define HV_X64_MSR_CRASH_CTL                    0x40000105
 #define HV_CRASH_CTL_NOTIFY                     (1ull << 63)
 
+/*
+ * Reenlightenment notification MSRs
+ */
+#define HV_X64_MSR_REENLIGHTENMENT_CONTROL      0x40000106
+#define HV_X64_MSR_TSC_EMULATION_CONTROL        0x40000107
+#define HV_X64_MSR_TSC_EMULATION_STATUS         0x40000108
+
 /*
  * Hypercall status code
  */
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index ad4b159b28..21e06deaf1 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -90,6 +90,7 @@ static bool has_msr_hv_runtime;
 static bool has_msr_hv_synic;
 static bool has_msr_hv_stimer;
 static bool has_msr_hv_frequencies;
+static bool has_msr_hv_reenlightenment;
 static bool has_msr_xss;
 static bool has_msr_spec_ctrl;
 
@@ -649,6 +650,11 @@ static int hyperv_handle_properties(CPUState *cs)
             env->features[FEAT_HYPERV_EAX] |= HV_ACCESS_FREQUENCY_MSRS;
             env->features[FEAT_HYPERV_EDX] |= HV_FREQUENCY_MSRS_AVAILABLE;
         }
+
+        if (has_msr_hv_reenlightenment) {
+            env->features[FEAT_HYPERV_EAX] |=
+                HV_ACCESS_REENLIGHTENMENTS_CONTROL;
+        }
     }
     if (cpu->hyperv_crash && has_msr_hv_crash) {
         env->features[FEAT_HYPERV_EDX] |= HV_GUEST_CRASH_MSR_AVAILABLE;
@@ -1154,6 +1160,9 @@ static int kvm_get_supported_msrs(KVMState *s)
                 case HV_X64_MSR_TSC_FREQUENCY:
                     has_msr_hv_frequencies = true;
                     break;
+                case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
+                    has_msr_hv_reenlightenment = true;
+                    break;
                 case MSR_IA32_SPEC_CTRL:
                     has_msr_spec_ctrl = true;
                     break;
@@ -1713,6 +1722,15 @@ static int kvm_put_msrs(X86CPU *cpu, int level)
             if (cpu->hyperv_time) {
                 kvm_msr_entry_add(cpu, HV_X64_MSR_REFERENCE_TSC,
                                   env->msr_hv_tsc);
+
+                if (has_msr_hv_reenlightenment) {
+                    kvm_msr_entry_add(cpu, HV_X64_MSR_REENLIGHTENMENT_CONTROL,
+                                      env->msr_hv_reenlightenment_control);
+                    kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_CONTROL,
+                                      env->msr_hv_tsc_emulation_control);
+                    kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_STATUS,
+                                      env->msr_hv_tsc_emulation_status);
+                }
             }
         }
         if (cpu->hyperv_vapic) {
@@ -2053,6 +2071,12 @@ static int kvm_get_msrs(X86CPU *cpu)
     }
     if (cpu->hyperv_time) {
         kvm_msr_entry_add(cpu, HV_X64_MSR_REFERENCE_TSC, 0);
+
+        if (has_msr_hv_reenlightenment) {
+            kvm_msr_entry_add(cpu, HV_X64_MSR_REENLIGHTENMENT_CONTROL, 0);
+            kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_CONTROL, 0);
+            kvm_msr_entry_add(cpu, HV_X64_MSR_TSC_EMULATION_STATUS, 0);
+        }
     }
     if (has_msr_hv_crash) {
         int j;
@@ -2294,6 +2318,15 @@ static int kvm_get_msrs(X86CPU *cpu)
             env->msr_hv_stimer_count[(index - HV_X64_MSR_STIMER0_COUNT)/2] =
                                 msrs[i].data;
             break;
+        case HV_X64_MSR_REENLIGHTENMENT_CONTROL:
+            env->msr_hv_reenlightenment_control = msrs[i].data;
+            break;
+        case HV_X64_MSR_TSC_EMULATION_CONTROL:
+            env->msr_hv_tsc_emulation_control = msrs[i].data;
+            break;
+        case HV_X64_MSR_TSC_EMULATION_STATUS:
+            env->msr_hv_tsc_emulation_status = msrs[i].data;
+            break;
         case MSR_MTRRdefType:
             env->mtrr_deftype = msrs[i].data;
             break;
-- 
2.14.3