[Qemu-devel] [PATCH 1/3] kvm/x86: Hyper-V HV_X64_MSR_RESET msr

[Denis V. Lunev]

From: Andrey Smetanin <address@hidden>

HV_X64_MSR_RESET msr is used by Hyper-V based Windows guest
to reset guest VM by hypervisor.

Necessary to support loading of winhv.sys in guest, which in turn is
required to support Windows VMBus.

Signed-off-by: Andrey Smetanin <address@hidden>
Reviewed-by: Roman Kagan <address@hidden>
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Paolo Bonzini <address@hidden>
CC: Gleb Natapov <address@hidden>
---
 arch/x86/include/uapi/asm/hyperv.h |  3 +++
 arch/x86/kvm/hyperv.c              | 10 ++++++++++
 arch/x86/kvm/x86.c                 |  7 +++++++
 include/linux/kvm_host.h           |  1 +
 4 files changed, 21 insertions(+)

diff --git a/arch/x86/include/uapi/asm/hyperv.h 
b/arch/x86/include/uapi/asm/hyperv.h
index f0412c5..dab584b 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -153,6 +153,9 @@
 /* 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/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index a8160d2..0ad11a2 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -41,6 +41,7 @@ static bool kvm_hv_msr_partition_wide(u32 msr)
        case HV_X64_MSR_TIME_REF_COUNT:
        case HV_X64_MSR_CRASH_CTL:
        case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
+       case HV_X64_MSR_RESET:
                r = true;
                break;
        }
@@ -163,6 +164,12 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 
msr, u64 data,
                                                 data);
        case HV_X64_MSR_CRASH_CTL:
                return kvm_hv_msr_set_crash_ctl(vcpu, data, host);
+       case HV_X64_MSR_RESET:
+               if (data == 1) {
+                       vcpu_debug(vcpu, "hyper-v reset requested\n");
+                       kvm_make_request(KVM_REQ_HV_RESET, vcpu);
+               }
+               break;
        default:
                vcpu_unimpl(vcpu, "Hyper-V uhandled wrmsr: 0x%x data 0x%llx\n",
                            msr, data);
@@ -241,6 +248,9 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 
msr, u64 *pdata)
                                                 pdata);
        case HV_X64_MSR_CRASH_CTL:
                return kvm_hv_msr_get_crash_ctl(vcpu, pdata);
+       case HV_X64_MSR_RESET:
+               data = 0;
+               break;
        default:
                vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
                return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a60bdbc..5a14a66 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -951,6 +951,7 @@ static u32 emulated_msrs[] = {
        HV_X64_MSR_TIME_REF_COUNT, HV_X64_MSR_REFERENCE_TSC,
        HV_X64_MSR_CRASH_P0, HV_X64_MSR_CRASH_P1, HV_X64_MSR_CRASH_P2,
        HV_X64_MSR_CRASH_P3, HV_X64_MSR_CRASH_P4, HV_X64_MSR_CRASH_CTL,
+       HV_X64_MSR_RESET,
        HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
        MSR_KVM_PV_EOI_EN,
 
@@ -6268,6 +6269,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                        r = 0;
                        goto out;
                }
+               if (kvm_check_request(KVM_REQ_HV_RESET, vcpu)) {
+                       vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
+                       vcpu->run->system_event.type = KVM_SYSTEM_EVENT_RESET;
+                       r = 0;
+                       goto out;
+               }
        }
 
        if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1bef9e2..f6beba2 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -140,6 +140,7 @@ static inline bool is_error_page(struct page *page)
 #define KVM_REQ_APIC_PAGE_RELOAD  25
 #define KVM_REQ_SMI               26
 #define KVM_REQ_HV_CRASH          27
+#define KVM_REQ_HV_RESET          28
 
 #define KVM_USERSPACE_IRQ_SOURCE_ID            0
 #define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID       1
-- 
2.1.4