KVM: VMX: cache exit_intr_info

[Marcelo Tosatti <mtosatti@redhat.com>]

exit_intr_info is read-only in nature, so once read it can be cached
similarly to idtv_vectoring_inf.

Reduces guest re-entry in about 50 cycles on my machine (the exception
path should be similar, but haven't measured).

Applies on top of register accessor patch.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

--- kvm.orig/arch/x86/kvm/vmx.c
+++ kvm/arch/x86/kvm/vmx.c
@@ -60,6 +60,7 @@ struct vcpu_vmx {
 	int                   launched;
 	u8                    fail;
 	u32                   idt_vectoring_info;
+	u32                   exit_intr_info;
 	struct kvm_msr_entry *guest_msrs;
 	struct kvm_msr_entry *host_msrs;
 	int                   nmsrs;
@@ -2250,7 +2251,7 @@ static int handle_exception(struct kvm_v
 	enum emulation_result er;
 
 	vect_info = vmx->idt_vectoring_info;
-	intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+	intr_info = vmx->exit_intr_info;
 
 	if ((vect_info & VECTORING_INFO_VALID_MASK) &&
 						!is_page_fault(intr_info))
@@ -2818,7 +2819,7 @@ static void vmx_intr_assist(struct kvm_v
 	update_tpr_threshold(vcpu);
 
 	intr_info_field = vmcs_read32(VM_ENTRY_INTR_INFO_FIELD);
-	exit_intr_info_field = vmcs_read32(VM_EXIT_INTR_INFO);
+	exit_intr_info_field = vmx->exit_intr_info;
 	idtv_info_field = vmx->idt_vectoring_info;
 	if (intr_info_field & INTR_INFO_VALID_MASK) {
 		if (idtv_info_field & INTR_INFO_VALID_MASK) {
@@ -2927,7 +2928,6 @@ static void vmx_flush_regs(struct kvm_vc
 static void vmx_vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	u32 intr_info;
 
 	vmx_flush_regs(vcpu);
 
@@ -3062,11 +3062,11 @@ static void vmx_vcpu_run(struct kvm_vcpu
 	asm("mov %0, %%ds; mov %0, %%es" : : "r"(__USER_DS));
 	vmx->launched = 1;
 
-	intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
+	vmx->exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
 
 	/* We need to handle NMIs before interrupts are enabled */
-	if ((intr_info & INTR_INFO_INTR_TYPE_MASK) == 0x200 &&
-	    (intr_info & INTR_INFO_VALID_MASK)) {
+	if ((vmx->exit_intr_info & INTR_INFO_INTR_TYPE_MASK) == 0x200 &&
+	    (vmx->exit_intr_info & INTR_INFO_VALID_MASK)) {
 		KVMTRACE_0D(NMI, vcpu, handler);
 		asm("int $2");
 	}