[PATCH] KVM: x86: Add emulation of MSR_SMI_COUNT

[Liran Alon <liran.alon@xxxxxxxxxx>]

This MSR returns the number of #SMIs that occurred on CPU since
boot.

It was seen to be used frequently by ESXi guest.

Patch adds a new vcpu-arch specific var called smi_count to
save the number of #SMIs which occurred on CPU since boot.
It is exposed as a read-only MSR to guest (causing #GP
on wrmsr) in RDMSR/WRMSR emulation code.
MSR_SMI_COUNT is also added to emulated_msrs[] to make sure
user-space can save/restore it for migration purposes.

Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Reviewed-by: Bhavesh Davda <bhavesh.davda@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---

Notes:
    To make vmsave/vload work for MSR_SMI_COUNT (for migration purposes),
    a patch for QEMU is also required.
    We have written such patch and verified that it works.
    It will be submitted seperately to the QEMU mailing list.

 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/x86.c              | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index c73e493adf07..089856eeac5d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -504,6 +504,7 @@ struct kvm_vcpu_arch {
 	int mp_state;
 	u64 ia32_misc_enable_msr;
 	u64 smbase;
+	u64 smi_count;
 	bool tpr_access_reporting;
 	u64 ia32_xss;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 21c00594f230..dedf5539f924 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1036,6 +1036,7 @@ bool kvm_rdpmc(struct kvm_vcpu *vcpu)
 	MSR_IA32_MCG_CTL,
 	MSR_IA32_MCG_EXT_CTL,
 	MSR_IA32_SMBASE,
+	MSR_SMI_COUNT,
 	MSR_PLATFORM_INFO,
 	MSR_MISC_FEATURES_ENABLES,
 };
@@ -2217,6 +2218,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		vcpu->arch.smbase = data;
 		break;
+	case MSR_SMI_COUNT:
+		if (!msr_info->host_initiated)
+			return 1;
+		vcpu->arch.smi_count = data;
+		break;
 	case MSR_KVM_WALL_CLOCK_NEW:
 	case MSR_KVM_WALL_CLOCK:
 		vcpu->kvm->arch.wall_clock = data;
@@ -2491,6 +2497,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			return 1;
 		msr_info->data = vcpu->arch.smbase;
 		break;
+	case MSR_SMI_COUNT:
+		msr_info->data = vcpu->arch.smi_count;
+		break;
 	case MSR_IA32_PERF_STATUS:
 		/* TSC increment by tick */
 		msr_info->data = 1000ULL;
@@ -6437,6 +6446,7 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool req_int_win)
 		kvm_x86_ops->queue_exception(vcpu);
 	} else if (vcpu->arch.smi_pending && !is_smm(vcpu)) {
 		vcpu->arch.smi_pending = false;
+		++vcpu->arch.smi_count;
 		enter_smm(vcpu);
 	} else if (vcpu->arch.nmi_pending && kvm_x86_ops->nmi_allowed(vcpu)) {
 		--vcpu->arch.nmi_pending;
@@ -7781,6 +7791,7 @@ void kvm_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	vcpu->arch.hflags = 0;
 
 	vcpu->arch.smi_pending = 0;
+	vcpu->arch.smi_count = 0;
 	atomic_set(&vcpu->arch.nmi_queued, 0);
 	vcpu->arch.nmi_pending = 0;
 	vcpu->arch.nmi_injected = false;
-- 
1.9.1