[FYI PATCH 15/20] kvm/x86: Hyper-V HV_X64_MSR_VP_RUNTIME support

[Paolo Bonzini <pbonzini@redhat.com>]

From: Andrey Smetanin <asmetanin@virtuozzo.com>

HV_X64_MSR_VP_RUNTIME msr used by guest to get
"the time the virtual processor consumes running guest code,
and the time the associated logical processor spends running
hypervisor code on behalf of that guest."

Calculation of this time is performed by task_cputime_adjusted()
for vcpu task.

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

Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Gleb Natapov <gleb@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/kvm_host.h    |  1 +
 arch/x86/include/uapi/asm/hyperv.h |  3 +++
 arch/x86/kvm/hyperv.c              | 21 +++++++++++++++++++--
 arch/x86/kvm/x86.c                 |  1 +
 kernel/sched/cputime.c             |  2 ++
 5 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 76a5b30979b3..d064cb2e19e8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -374,6 +374,7 @@ struct kvm_mtrr {
 /* Hyper-V per vcpu emulation context */
 struct kvm_vcpu_hv {
 	u64 hv_vapic;
+	s64 runtime_offset;
 };
 
 struct kvm_vcpu_arch {
diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
index dab584bf7ddf..2677a0aac2cc 100644
--- a/arch/x86/include/uapi/asm/hyperv.h
+++ b/arch/x86/include/uapi/asm/hyperv.h
@@ -156,6 +156,9 @@
 /* MSR used to reset the guest OS. */
 #define HV_X64_MSR_RESET			0x40000003
 
+/* MSR used to provide vcpu runtime in 100ns units */
+#define HV_X64_MSR_VP_RUNTIME			0x40000010
+
 /* 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 0ad11a232474..62cf8c915e95 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -178,7 +178,16 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 	return 0;
 }
 
-static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
+/* Calculate cpu time spent by current task in 100ns units */
+static u64 current_task_runtime_100ns(void)
+{
+	cputime_t utime, stime;
+
+	task_cputime_adjusted(current, &utime, &stime);
+	return div_u64(cputime_to_nsecs(utime + stime), 100);
+}
+
+static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 {
 	struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;
 
@@ -212,6 +221,11 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		return kvm_hv_vapic_msr_write(vcpu, APIC_ICR, data);
 	case HV_X64_MSR_TPR:
 		return kvm_hv_vapic_msr_write(vcpu, APIC_TASKPRI, data);
+	case HV_X64_MSR_VP_RUNTIME:
+		if (!host)
+			return 1;
+		hv->runtime_offset = data - current_task_runtime_100ns();
+		break;
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V uhandled wrmsr: 0x%x data 0x%llx\n",
 			    msr, data);
@@ -287,6 +301,9 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case HV_X64_MSR_APIC_ASSIST_PAGE:
 		data = hv->hv_vapic;
 		break;
+	case HV_X64_MSR_VP_RUNTIME:
+		data = current_task_runtime_100ns() + hv->runtime_offset;
+		break;
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V unhandled rdmsr: 0x%x\n", msr);
 		return 1;
@@ -305,7 +322,7 @@ int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 		mutex_unlock(&vcpu->kvm->lock);
 		return r;
 	} else
-		return kvm_hv_set_msr(vcpu, msr, data);
+		return kvm_hv_set_msr(vcpu, msr, data, host);
 }
 
 int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5bc598de28a7..3e4d03220650 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -954,6 +954,7 @@ static u32 emulated_msrs[] = {
 	HV_X64_MSR_CRASH_P3, HV_X64_MSR_CRASH_P4, HV_X64_MSR_CRASH_CTL,
 	HV_X64_MSR_RESET,
 	HV_X64_MSR_VP_INDEX,
+	HV_X64_MSR_VP_RUNTIME,
 	HV_X64_MSR_APIC_ASSIST_PAGE, MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
 	MSR_KVM_PV_EOI_EN,
 
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 8cbc3db671df..26a54461bf59 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -444,6 +444,7 @@ void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
 	*ut = p->utime;
 	*st = p->stime;
 }
+EXPORT_SYMBOL_GPL(task_cputime_adjusted);
 
 void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
 {
@@ -652,6 +653,7 @@ void task_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
 	task_cputime(p, &cputime.utime, &cputime.stime);
 	cputime_adjust(&cputime, &p->prev_cputime, ut, st);
 }
+EXPORT_SYMBOL_GPL(task_cputime_adjusted);
 
 void thread_group_cputime_adjusted(struct task_struct *p, cputime_t *ut, cputime_t *st)
 {
-- 
1.8.3.1