KVM: nVMX: do early preparation of vmcs02 before check_vmentry_postreqs()

In anticipation of using vmcs02 to do early consistency checks, move
the early preparation of vmcs02 prior to checking the postreqs.  The
downside of this approach is that we'll unnecessary load vmcs02 in
the case that check_vmentry_postreqs() fails, but that is essentially
our slow path anyways (not actually slow, but it's the path we don't
really care about optimizing).
Signed-off-by: NSean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: NJim Mattson <jmattson@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -12701,11 +12701,6 @@ static int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 	if (likely(!evaluate_pending_interrupts) && kvm_vcpu_apicv_active(vcpu))
 		evaluate_pending_interrupts |= vmx_has_apicv_interrupt(vcpu);
 
-	if (from_vmentry && check_vmentry_postreqs(vcpu, vmcs12, &exit_qual))
-		goto vmentry_fail_vmexit;
-
-	enter_guest_mode(vcpu);
-
 	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
 		vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
 	if (kvm_mpx_supported() &&
@@ -12714,17 +12709,23 @@ static int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 
 	vmx_switch_vmcs(vcpu, &vmx->nested.vmcs02);
 
+	prepare_vmcs02_early(vmx, vmcs12);
+
+	if (from_vmentry) {
+		nested_get_vmcs12_pages(vcpu);
+
+		if (check_vmentry_postreqs(vcpu, vmcs12, &exit_qual))
+			goto vmentry_fail_vmexit;
+	}
+
+	enter_guest_mode(vcpu);
 	if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
 		vcpu->arch.tsc_offset += vmcs12->tsc_offset;
 
-	prepare_vmcs02_early(vmx, vmcs12);
-
 	if (prepare_vmcs02(vcpu, vmcs12, &exit_qual))
 		goto vmentry_fail_vmexit_guest_mode;
 
 	if (from_vmentry) {
-		nested_get_vmcs12_pages(vcpu);
-
 		exit_reason = EXIT_REASON_MSR_LOAD_FAIL;
 		exit_qual = nested_vmx_load_msr(vcpu,
 						vmcs12->vm_entry_msr_load_addr,
@@ -12776,12 +12777,13 @@ static int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
 	if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)
 		vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
 	leave_guest_mode(vcpu);
+
+vmentry_fail_vmexit:
 	vmx_switch_vmcs(vcpu, &vmx->vmcs01);
 
 	if (!from_vmentry)
 		return 1;
 
-vmentry_fail_vmexit:
 	load_vmcs12_host_state(vcpu, vmcs12);
 	vmcs12->vm_exit_reason = exit_reason | VMX_EXIT_REASONS_FAILED_VMENTRY;
 	vmcs12->exit_qualification = exit_qual;