KVM: VMX: Move skip_emulated_instruction out of nested_vmx_check_vmcs12

We can't return both the pass/fail boolean for the vmcs and the upcoming
continue/exit-to-userspace boolean for skip_emulated_instruction out of
nested_vmx_check_vmcs, so move skip_emulated_instruction out of it instead.

Additionally, VMENTER/VMRESUME only trigger singlestep exceptions when
they advance the IP to the following instruction, not when they a) succeed,
b) fail MSR validation or c) throw an exception. Add a separate call to
skip_emulated_instruction that will later not be converted to the variant
that checks the singlestep flag.

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/vmx.c

@@ -7324,7 +7324,6 @@ static int nested_vmx_check_vmcs12(struct kvm_vcpu *vcpu)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	if (vmx->nested.current_vmptr == -1ull) {
 		nested_vmx_failInvalid(vcpu);
-		skip_emulated_instruction(vcpu);
 		return 0;
 	}
 	return 1;
@@ -7338,9 +7337,13 @@ static int handle_vmread(struct kvm_vcpu *vcpu)
 	u32 vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
 	gva_t gva = 0;
 
-	if (!nested_vmx_check_permission(vcpu) ||
-	    !nested_vmx_check_vmcs12(vcpu))
+	if (!nested_vmx_check_permission(vcpu))
+		return 1;
+
+	if (!nested_vmx_check_vmcs12(vcpu)) {
+		skip_emulated_instruction(vcpu);
 		return 1;
+	}
 
 	/* Decode instruction info and find the field to read */
 	field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
@@ -7388,10 +7391,14 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu)
 	u64 field_value = 0;
 	struct x86_exception e;
 
-	if (!nested_vmx_check_permission(vcpu) ||
-	    !nested_vmx_check_vmcs12(vcpu))
+	if (!nested_vmx_check_permission(vcpu))
 		return 1;
 
+	if (!nested_vmx_check_vmcs12(vcpu)) {
+		skip_emulated_instruction(vcpu);
+		return 1;
+	}
+
 	if (vmx_instruction_info & (1u << 10))
 		field_value = kvm_register_readl(vcpu,
 			(((vmx_instruction_info) >> 3) & 0xf));
@@ -10046,11 +10053,12 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	bool ia32e;
 	u32 msr_entry_idx;
 
-	if (!nested_vmx_check_permission(vcpu) ||
-	    !nested_vmx_check_vmcs12(vcpu))
+	if (!nested_vmx_check_permission(vcpu))
 		return 1;
 
-	skip_emulated_instruction(vcpu);
+	if (!nested_vmx_check_vmcs12(vcpu))
+		goto out;
+
 	vmcs12 = get_vmcs12(vcpu);
 
 	if (enable_shadow_vmcs)
@@ -10070,33 +10078,33 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 		nested_vmx_failValid(vcpu,
 			launch ? VMXERR_VMLAUNCH_NONCLEAR_VMCS
 			       : VMXERR_VMRESUME_NONLAUNCHED_VMCS);
-		return 1;
+		goto out;
 	}
 
 	if (vmcs12->guest_activity_state != GUEST_ACTIVITY_ACTIVE &&
 	    vmcs12->guest_activity_state != GUEST_ACTIVITY_HLT) {
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (!nested_get_vmcs12_pages(vcpu, vmcs12)) {
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (nested_vmx_check_msr_bitmap_controls(vcpu, vmcs12)) {
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (nested_vmx_check_apicv_controls(vcpu, vmcs12)) {
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (nested_vmx_check_msr_switch_controls(vcpu, vmcs12)) {
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (!vmx_control_verify(vmcs12->cpu_based_vm_exec_control,
@@ -10116,26 +10124,26 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 				vmx->nested.nested_vmx_entry_ctls_high))
 	{
 		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (((vmcs12->host_cr0 & VMXON_CR0_ALWAYSON) != VMXON_CR0_ALWAYSON) ||
 	    ((vmcs12->host_cr4 & VMXON_CR4_ALWAYSON) != VMXON_CR4_ALWAYSON)) {
 		nested_vmx_failValid(vcpu,
 			VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
-		return 1;
+		goto out;
 	}
 
 	if (!nested_cr0_valid(vcpu, vmcs12->guest_cr0) ||
 	    ((vmcs12->guest_cr4 & VMXON_CR4_ALWAYSON) != VMXON_CR4_ALWAYSON)) {
 		nested_vmx_entry_failure(vcpu, vmcs12,
 			EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
-		return 1;
+		goto out;
 	}
 	if (vmcs12->vmcs_link_pointer != -1ull) {
 		nested_vmx_entry_failure(vcpu, vmcs12,
 			EXIT_REASON_INVALID_STATE, ENTRY_FAIL_VMCS_LINK_PTR);
-		return 1;
+		goto out;
 	}
 
 	/*
@@ -10155,7 +10163,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 		     ia32e != !!(vmcs12->guest_ia32_efer & EFER_LME))) {
 			nested_vmx_entry_failure(vcpu, vmcs12,
 				EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
-			return 1;
+			goto out;
 		}
 	}
 
@@ -10173,7 +10181,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 		    ia32e != !!(vmcs12->host_ia32_efer & EFER_LME)) {
 			nested_vmx_entry_failure(vcpu, vmcs12,
 				EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
-			return 1;
+			goto out;
 		}
 	}
 
@@ -10186,6 +10194,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	if (!vmcs02)
 		return -ENOMEM;
 
+	skip_emulated_instruction(vcpu);
 	enter_guest_mode(vcpu);
 
 	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
@@ -10227,6 +10236,10 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	 * the success flag) when L2 exits (see nested_vmx_vmexit()).
 	 */
 	return 1;
+
+out:
+	skip_emulated_instruction(vcpu);
+	return 1;
 }
 
 /*