KVM: Split cpuid register access from computation

Introduce kvm_cpuid() to perform the leaf limit check and calculate
register values, and let kvm_emulate_cpuid() just handle reading and
writing the registers from/to the vcpu.  This allows us to reuse
kvm_cpuid() in a context where directly reading and writing registers
is not desired.

Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
index 26d1fb4..f449edc 100644
--- a/arch/x86/kvm/cpuid.h
+++ b/arch/x86/kvm/cpuid.h
@@ -17,6 +17,7 @@
 int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
 			      struct kvm_cpuid2 *cpuid,
 			      struct kvm_cpuid_entry2 __user *entries);
+void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
 
 
 static inline bool guest_cpuid_has_xsave(struct kvm_vcpu *vcpu)