[Qemu-devel] [PATCH 1/3] target-i386/kvm: Hyper-V HV_X64_MSR_RESET support

["Denis V. Lunev" <den@openvz.org>]

From: Andrey Smetanin <asmetanin@virtuozzo.com>

HV_X64_MSR_RESET msr is used by Hyper-V based Windows guest
to reset guest VM by hypervisor. This msr is stateless so
no migration/fetch/update is required.

This code checks cpu option "hv-reset" and support by
kernel. If both conditions are met appropriate Hyper-V features
cpuid bit is set.

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Eduardo Habkost <ehabkost@redhat.com>
CC: "Andreas Färber" <afaerber@suse.de>
CC: Marcelo Tosatti <mtosatti@redhat.com>
---
 linux-headers/asm-x86/hyperv.h |  3 +++
 target-i386/cpu-qom.h          |  1 +
 target-i386/cpu.c              |  1 +
 target-i386/kvm.c              | 11 ++++++++++-
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/linux-headers/asm-x86/hyperv.h b/linux-headers/asm-x86/hyperv.h
index 8fba544..ba3a63b 100644
--- a/linux-headers/asm-x86/hyperv.h
+++ b/linux-headers/asm-x86/hyperv.h
@@ -149,6 +149,9 @@
 /* MSR used to provide vcpu index */
 #define HV_X64_MSR_VP_INDEX			0x40000002
 
+/* MSR used to reset the guest OS. */
+#define HV_X64_MSR_RESET               0x40000003
+
 /* MSR used to read the per-partition time reference counter */
 #define HV_X64_MSR_TIME_REF_COUNT		0x40000020
 
diff --git a/target-i386/cpu-qom.h b/target-i386/cpu-qom.h
index 7a4fddd..3789a2f 100644
--- a/target-i386/cpu-qom.h
+++ b/target-i386/cpu-qom.h
@@ -89,6 +89,7 @@ typedef struct X86CPU {
     bool hyperv_relaxed_timing;
     int hyperv_spinlock_attempts;
     bool hyperv_time;
+    bool hyperv_reset;
     bool check_cpuid;
     bool enforce_cpuid;
     bool expose_kvm;
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index cfb8aa7..21828ad 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -3121,6 +3121,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_BOOL("hv-relaxed", X86CPU, hyperv_relaxed_timing, false),
     DEFINE_PROP_BOOL("hv-vapic", X86CPU, hyperv_vapic, false),
     DEFINE_PROP_BOOL("hv-time", X86CPU, hyperv_time, false),
+    DEFINE_PROP_BOOL("hv-reset", X86CPU, hyperv_reset, false),
     DEFINE_PROP_BOOL("check", X86CPU, check_cpuid, false),
     DEFINE_PROP_BOOL("enforce", X86CPU, enforce_cpuid, false),
     DEFINE_PROP_BOOL("kvm", X86CPU, expose_kvm, true),
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 066d03d..37e82fb 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -80,6 +80,7 @@ static int lm_capable_kernel;
 static bool has_msr_hv_hypercall;
 static bool has_msr_hv_vapic;
 static bool has_msr_hv_tsc;
+static bool has_msr_hv_reset;
 static bool has_msr_mtrr;
 static bool has_msr_xss;
 
@@ -457,7 +458,8 @@ static bool hyperv_enabled(X86CPU *cpu)
     return kvm_check_extension(cs->kvm_state, KVM_CAP_HYPERV) > 0 &&
            (hyperv_hypercall_available(cpu) ||
             cpu->hyperv_time  ||
-            cpu->hyperv_relaxed_timing);
+            cpu->hyperv_relaxed_timing ||
+            cpu->hyperv_reset);
 }
 
 static Error *invtsc_mig_blocker;
@@ -523,6 +525,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
             c->eax |= 0x200;
             has_msr_hv_tsc = true;
         }
+        if (cpu->hyperv_reset && has_msr_hv_reset) {
+            c->eax |= HV_X64_MSR_RESET_AVAILABLE;
+        }
         c = &cpuid_data.entries[cpuid_i++];
         c->function = HYPERV_CPUID_ENLIGHTMENT_INFO;
         if (cpu->hyperv_relaxed_timing) {
@@ -843,6 +848,10 @@ static int kvm_get_supported_msrs(KVMState *s)
                     has_msr_xss = true;
                     continue;
                 }
+                if (kvm_msr_list->indices[i] == HV_X64_MSR_RESET) {
+                    has_msr_hv_reset = true;
+                    continue;
+                }
             }
         }
 
-- 
2.1.4