KVM: Add generic RDPMC support

Add a helper function that emulates the RDPMC instruction operation.
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -760,6 +760,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data);
 
 unsigned long kvm_get_rflags(struct kvm_vcpu *vcpu);
 void kvm_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags);
+bool kvm_rdpmc(struct kvm_vcpu *vcpu);
 
 void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr);
 void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code);

arch/x86/kvm/x86.c

@@ -760,6 +760,21 @@ int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)
 }
 EXPORT_SYMBOL_GPL(kvm_get_dr);
 
+bool kvm_rdpmc(struct kvm_vcpu *vcpu)
+{
+	u32 ecx = kvm_register_read(vcpu, VCPU_REGS_RCX);
+	u64 data;
+	int err;
+
+	err = kvm_pmu_read_pmc(vcpu, ecx, &data);
+	if (err)
+		return err;
+	kvm_register_write(vcpu, VCPU_REGS_RAX, (u32)data);
+	kvm_register_write(vcpu, VCPU_REGS_RDX, data >> 32);
+	return err;
+}
+EXPORT_SYMBOL_GPL(kvm_rdpmc);
+
 /*
  * List of msr numbers which we expose to userspace through KVM_GET_MSRS
  * and KVM_SET_MSRS, and KVM_GET_MSR_INDEX_LIST.