Re: [Qemu-devel] [PATCH v5 1/1] i386/kvm: add support for Hyper-V reenlightenment MSRs

[Roman Kagan]

On Wed, Apr 11, 2018 at 01:50:36PM +0200, Vitaly Kuznetsov wrote:
> 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 
> ---
> Changes since v4:
> - Rebase on top of Roman's patches.
> ---
>  target/i386/cpu.c  |  4 +++-
>  target/i386/cpu.h  |  4 
>  target/i386/hyperv-proto.h |  9 -
>  target/i386/kvm.c  | 39 ++-
>  target/i386/machine.c  | 24 
>  5 files changed, 77 insertions(+), 3 deletions(-)

Reviewed-by: Roman Kagan 

[Qemu-devel] [PATCH v5 1/1] i386/kvm: add support for Hyper-V reenlightenment MSRs

[Vitaly Kuznetsov]

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 
---
Changes since v4:
- Rebase on top of Roman's patches.
---
 target/i386/cpu.c  |  4 +++-
 target/i386/cpu.h  |  4 
 target/i386/hyperv-proto.h |  9 -
 target/i386/kvm.c  | 39 ++-
 target/i386/machine.c  | 24 
 5 files changed, 77 insertions(+), 3 deletions(-)

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 1a6b082b6f..e0e7a16d21 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -409,7 +409,8 @@ static FeatureWordInfo feature_word_info[FEATURE_WORDS] = {
 NULL /* hv_vpindex_access */, NULL /* hv_msr_reset_access */,
 NULL /* hv_msr_stats_access */, NULL /* hv_reftsc_access */,
 NULL /* hv_msr_idle_access */, NULL /* hv_msr_frequency_access */,
-NULL, NULL, NULL, NULL,
+NULL /* hv_msr_debug_access */, NULL /* 
hv_msr_reenlightenment_access */,
+NULL, NULL,
 NULL, NULL, NULL, NULL,
 NULL, NULL, NULL, NULL,
 NULL, NULL, NULL, NULL,
@@ -4762,6 +4763,7 @@ static Property x86_cpu_properties[] = {
 DEFINE_PROP_BOOL("hv-synic", X86CPU, hyperv_synic, false),
 DEFINE_PROP_BOOL("hv-stimer", X86CPU, hyperv_stimer, false),
 DEFINE_PROP_BOOL("hv-frequencies", X86CPU, hyperv_frequencies, false),
+DEFINE_PROP_BOOL("hv-reenlightenment", X86CPU, hyperv_reenlightenment, 
false),
 DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, true),
 DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
 DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index 1b219fafc4..b58b779bff 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -1174,6 +1174,9 @@ 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;
 
 uint64_t msr_rtit_ctrl;
 uint64_t msr_rtit_status;
@@ -1297,6 +1300,7 @@ struct X86CPU {
 bool hyperv_synic;
 bool hyperv_stimer;
 bool hyperv_frequencies;
+bool hyperv_reenlightenment;
 bool check_cpuid;
 bool enforce_cpuid;
 bool expose_kvm;
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_CTL0x4105
 #define HV_CRASH_CTL_NOTIFY (1ull << 63)
 
+/*
+ * Reenlightenment notification MSRs
+ */
+#define HV_X64_MSR_REENLIGHTENMENT_CONTROL  0x4106
+#define HV_X64_MSR_TSC_EMULATION_CONTROL0x4107
+#define HV_X64_MSR_TSC_EMULATION_STATUS 0x4108
+
 /*
  * Hypercall status code
  */
diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index 6c49954e68..da4b19 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;
 static bool has_msr_smi_count;
@@ -583,7 +584,8 @@ static bool hyperv_enabled(X86CPU *cpu)
 cpu->hyperv_vpindex ||
 cpu->hyperv_runtime ||
 cpu->hyperv_synic ||
-cpu->hyperv_stimer);
+cpu->hyperv_stimer ||
+cpu->hyperv_reenlightenment);
 }
 
 static int kvm_arch_set_tsc_khz(CPUState *cs)
@@ -669,6 +671,16 @@ static int hyperv_handle_properties(CPUState *cs)
 }
 env->features[FEAT_HYPERV_EDX] |= HV_GUEST_CRASH_MSR_AVAILABLE;
 }
+if (cpu->hyperv_reenlightenment) {
+if (!has_msr_hv_reenlightenment) {
+fprintf(stderr,
+"Hyper-V Reenlightenment MSRs "
+"(requested by 'hv-reenlightenment' cpu flag) "
+"are not supported by kernel\n");
+return -ENOSYS;
+}
+env->features[FEAT_HYPERV_EAX] |= HV_ACCESS_REENLIGHTENMENTS_CONTROL;
+}
 env->features[FEAT_HYPERV_EDX] |= HV_CPU_DYNAMIC_PARTITIONING_AVAILABLE;
 if (cpu->hyperv_reset) {
 if (!has_msr_hv_reset) {
@@ -1215,6 +1227,9 @@