kvm: nVMX: Split VMCS checks from nested_vmx_run()

The checks performed on the contents of the vmcs12 are extracted from
nested_vmx_run so that they can be used to validate a vmcs12 that has
been restored from a checkpoint.
Signed-off-by: Jim Mattson <jmattson@google.com>
[Change prepare_vmcs02 and nested_vmx_load_cr3's last argument to u32,
 to match check_vmentry_postreqs.  Update comments for singlestep
 handling. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -10035,7 +10035,7 @@ static bool nested_cr3_valid(struct kvm_vcpu *vcpu, unsigned long val)
  * is assigned to entry_failure_code on failure.
  */
 static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool nested_ept,
-			       unsigned long *entry_failure_code)
+			       u32 *entry_failure_code)
 {
 	if (cr3 != kvm_read_cr3(vcpu) || (!nested_ept && pdptrs_changed(vcpu))) {
 		if (!nested_cr3_valid(vcpu, cr3)) {
@@ -10075,7 +10075,7 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
  * is assigned to entry_failure_code on failure.
  */
 static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
-			  bool from_vmentry, unsigned long *entry_failure_code)
+			  bool from_vmentry, u32 *entry_failure_code)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	u32 exec_control;
@@ -10411,68 +10411,22 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	return 0;
 }
 
-/*
- * nested_vmx_run() handles a nested entry, i.e., a VMLAUNCH or VMRESUME on L1
- * for running an L2 nested guest.
- */
-static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
+static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 {
-	struct vmcs12 *vmcs12;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	int cpu;
-	struct loaded_vmcs *vmcs02;
-	bool ia32e;
-	u32 msr_entry_idx;
-	unsigned long exit_qualification;
-
-	if (!nested_vmx_check_permission(vcpu))
-		return 1;
-
-	if (!nested_vmx_check_vmcs12(vcpu))
-		goto out;
-
-	vmcs12 = get_vmcs12(vcpu);
-
-	if (enable_shadow_vmcs)
-		copy_shadow_to_vmcs12(vmx);
-
-	/*
-	 * The nested entry process starts with enforcing various prerequisites
-	 * on vmcs12 as required by the Intel SDM, and act appropriately when
-	 * they fail: As the SDM explains, some conditions should cause the
-	 * instruction to fail, while others will cause the instruction to seem
-	 * to succeed, but return an EXIT_REASON_INVALID_STATE.
-	 * To speed up the normal (success) code path, we should avoid checking
-	 * for misconfigurations which will anyway be caught by the processor
-	 * when using the merged vmcs02.
-	 */
-	if (vmcs12->launch_state == launch) {
-		nested_vmx_failValid(vcpu,
-			launch ? VMXERR_VMLAUNCH_NONCLEAR_VMCS
-			       : VMXERR_VMRESUME_NONLAUNCHED_VMCS);
-		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);
-		goto out;
-	}
+	    vmcs12->guest_activity_state != GUEST_ACTIVITY_HLT)
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
 
-	if (nested_vmx_check_msr_bitmap_controls(vcpu, vmcs12)) {
-		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		goto out;
-	}
+	if (nested_vmx_check_msr_bitmap_controls(vcpu, vmcs12))
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
 
-	if (nested_vmx_check_apicv_controls(vcpu, vmcs12)) {
-		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		goto out;
-	}
+	if (nested_vmx_check_apicv_controls(vcpu, vmcs12))
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
 
-	if (nested_vmx_check_msr_switch_controls(vcpu, vmcs12)) {
-		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		goto out;
-	}
+	if (nested_vmx_check_msr_switch_controls(vcpu, vmcs12))
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
 
 	if (!vmx_control_verify(vmcs12->cpu_based_vm_exec_control,
 				vmx->nested.nested_vmx_procbased_ctls_low,
@@ -10489,28 +10443,30 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	    !vmx_control_verify(vmcs12->vm_entry_controls,
 				vmx->nested.nested_vmx_entry_ctls_low,
 				vmx->nested.nested_vmx_entry_ctls_high))
-	{
-		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
-		goto out;
-	}
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
 
 	if (!nested_host_cr0_valid(vcpu, vmcs12->host_cr0) ||
 	    !nested_host_cr4_valid(vcpu, vmcs12->host_cr4) ||
-	    !nested_cr3_valid(vcpu, vmcs12->host_cr3)) {
-		nested_vmx_failValid(vcpu,
-			VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
-		goto out;
-	}
+	    !nested_cr3_valid(vcpu, vmcs12->host_cr3))
+		return VMXERR_ENTRY_INVALID_HOST_STATE_FIELD;
+
+	return 0;
+}
+
+static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
+				  u32 *exit_qual)
+{
+	bool ia32e;
+
+	*exit_qual = ENTRY_FAIL_DEFAULT;
 
 	if (!nested_guest_cr0_valid(vcpu, vmcs12->guest_cr0) ||
-	    !nested_guest_cr4_valid(vcpu, vmcs12->guest_cr4)) {
-		nested_vmx_entry_failure(vcpu, vmcs12,
-			EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
+	    !nested_guest_cr4_valid(vcpu, vmcs12->guest_cr4))
 		return 1;
-	}
-	if (vmcs12->vmcs_link_pointer != -1ull) {
-		nested_vmx_entry_failure(vcpu, vmcs12,
-			EXIT_REASON_INVALID_STATE, ENTRY_FAIL_VMCS_LINK_PTR);
+
+	if (!nested_cpu_has2(vmcs12, SECONDARY_EXEC_SHADOW_VMCS) &&
+	    vmcs12->vmcs_link_pointer != -1ull) {
+		*exit_qual = ENTRY_FAIL_VMCS_LINK_PTR;
 		return 1;
 	}
 
@@ -10523,17 +10479,15 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	 *   to bit 8 (LME) if bit 31 in the CR0 field (corresponding to
 	 *   CR0.PG) is 1.
 	 */
-	if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER) {
+	if (to_vmx(vcpu)->nested.nested_run_pending &&
+	    (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_EFER)) {
 		ia32e = (vmcs12->vm_entry_controls & VM_ENTRY_IA32E_MODE) != 0;
 		if (!kvm_valid_efer(vcpu, vmcs12->guest_ia32_efer) ||
 		    ia32e != !!(vmcs12->guest_ia32_efer & EFER_LMA) ||
 		    ((vmcs12->guest_cr0 & X86_CR0_PG) &&
-		     ia32e != !!(vmcs12->guest_ia32_efer & EFER_LME))) {
-			nested_vmx_entry_failure(vcpu, vmcs12,
-				EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
+		     ia32e != !!(vmcs12->guest_ia32_efer & EFER_LME)))
 			return 1;
 	}
-	}
 
 	/*
 	 * If the load IA32_EFER VM-exit control is 1, bits reserved in the
@@ -10546,11 +10500,75 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 			 VM_EXIT_HOST_ADDR_SPACE_SIZE) != 0;
 		if (!kvm_valid_efer(vcpu, vmcs12->host_ia32_efer) ||
 		    ia32e != !!(vmcs12->host_ia32_efer & EFER_LMA) ||
-		    ia32e != !!(vmcs12->host_ia32_efer & EFER_LME)) {
-			nested_vmx_entry_failure(vcpu, vmcs12,
-				EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
+		    ia32e != !!(vmcs12->host_ia32_efer & EFER_LME))
 			return 1;
 	}
+
+	return 0;
+}
+
+/*
+ * nested_vmx_run() handles a nested entry, i.e., a VMLAUNCH or VMRESUME on L1
+ * for running an L2 nested guest.
+ */
+static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
+{
+	struct vmcs12 *vmcs12;
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	int cpu;
+	struct loaded_vmcs *vmcs02;
+	u32 msr_entry_idx;
+	u32 exit_qual;
+	int ret;
+
+	if (!nested_vmx_check_permission(vcpu))
+		return 1;
+
+	if (!nested_vmx_check_vmcs12(vcpu))
+		goto out;
+
+	vmcs12 = get_vmcs12(vcpu);
+
+	if (enable_shadow_vmcs)
+		copy_shadow_to_vmcs12(vmx);
+
+	/*
+	 * The nested entry process starts with enforcing various prerequisites
+	 * on vmcs12 as required by the Intel SDM, and act appropriately when
+	 * they fail: As the SDM explains, some conditions should cause the
+	 * instruction to fail, while others will cause the instruction to seem
+	 * to succeed, but return an EXIT_REASON_INVALID_STATE.
+	 * To speed up the normal (success) code path, we should avoid checking
+	 * for misconfigurations which will anyway be caught by the processor
+	 * when using the merged vmcs02.
+	 */
+	if (vmcs12->launch_state == launch) {
+		nested_vmx_failValid(vcpu,
+			launch ? VMXERR_VMLAUNCH_NONCLEAR_VMCS
+			       : VMXERR_VMRESUME_NONLAUNCHED_VMCS);
+		goto out;
+	}
+
+	ret = check_vmentry_prereqs(vcpu, vmcs12);
+	if (ret) {
+		nested_vmx_failValid(vcpu, ret);
+		goto out;
+	}
+
+	/*
+	 * After this point, the trap flag no longer triggers a singlestep trap
+	 * on the vm entry instructions; don't call kvm_skip_emulated_instruction.
+	 * This is not 100% correct; for performance reasons, we delegate most
+	 * of the checks on host state to the processor.  If those fail,
+	 * the singlestep trap is missed.
+	 */
+	skip_emulated_instruction(vcpu);
+
+	ret = check_vmentry_postreqs(vcpu, vmcs12, &exit_qual);
+	if (ret) {
+		nested_vmx_entry_failure(vcpu, vmcs12,
+					 EXIT_REASON_INVALID_STATE, exit_qual);
+		return 1;
 	}
 
 	/*
@@ -10562,12 +10580,6 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	if (!vmcs02)
 		return -ENOMEM;
 
-	/*
-	 * After this point, the trap flag no longer triggers a singlestep trap
-	 * on the vm entry instructions. Don't call
-	 * kvm_skip_emulated_instruction.
-	 */
-	skip_emulated_instruction(vcpu);
 	enter_guest_mode(vcpu);
 
 	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
@@ -10582,11 +10594,11 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 
 	vmx_segment_cache_clear(vmx);
 
-	if (prepare_vmcs02(vcpu, vmcs12, true, &exit_qualification)) {
+	if (prepare_vmcs02(vcpu, vmcs12, true, &exit_qual)) {
 		leave_guest_mode(vcpu);
 		vmx_load_vmcs01(vcpu);
 		nested_vmx_entry_failure(vcpu, vmcs12,
-				EXIT_REASON_INVALID_STATE, exit_qualification);
+				EXIT_REASON_INVALID_STATE, exit_qual);
 		return 1;
 	}
 
@@ -10937,7 +10949,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 				   struct vmcs12 *vmcs12)
 {
 	struct kvm_segment seg;
-	unsigned long entry_failure_code;
+	u32 entry_failure_code;
 
 	if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER)
 		vcpu->arch.efer = vmcs12->host_ia32_efer;