kvm: nVMX: Refactor nested_vmx_run()

Nested_vmx_run is split into two parts: the part that handles the
VMLAUNCH/VMRESUME instruction, and the part that modifies the vcpu state
to transition from VMX root mode to VMX non-root mode. The latter will
be used when restoring the checkpointed state of a vCPU that was in VMX
operation when a snapshot was taken.

Signed-off-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -10507,6 +10507,65 @@ static int check_vmentry_postreqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	return 0;
 }
 
+static int enter_vmx_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+	struct loaded_vmcs *vmcs02;
+	int cpu;
+	u32 msr_entry_idx;
+	u32 exit_qual;
+
+	vmcs02 = nested_get_current_vmcs02(vmx);
+	if (!vmcs02)
+		return -ENOMEM;
+
+	enter_guest_mode(vcpu);
+
+	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
+		vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
+
+	cpu = get_cpu();
+	vmx->loaded_vmcs = vmcs02;
+	vmx_vcpu_put(vcpu);
+	vmx_vcpu_load(vcpu, cpu);
+	vcpu->cpu = cpu;
+	put_cpu();
+
+	vmx_segment_cache_clear(vmx);
+
+	if (prepare_vmcs02(vcpu, vmcs12, from_vmentry, &exit_qual)) {
+		leave_guest_mode(vcpu);
+		vmx_load_vmcs01(vcpu);
+		nested_vmx_entry_failure(vcpu, vmcs12,
+					 EXIT_REASON_INVALID_STATE, exit_qual);
+		return 1;
+	}
+
+	nested_get_vmcs12_pages(vcpu, vmcs12);
+
+	msr_entry_idx = nested_vmx_load_msr(vcpu,
+					    vmcs12->vm_entry_msr_load_addr,
+					    vmcs12->vm_entry_msr_load_count);
+	if (msr_entry_idx) {
+		leave_guest_mode(vcpu);
+		vmx_load_vmcs01(vcpu);
+		nested_vmx_entry_failure(vcpu, vmcs12,
+				EXIT_REASON_MSR_LOAD_FAIL, msr_entry_idx);
+		return 1;
+	}
+
+	vmcs12->launch_state = 1;
+
+	/*
+	 * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
+	 * we are no longer running L1, and VMLAUNCH/VMRESUME has not yet
+	 * returned as far as L1 is concerned. It will only return (and set
+	 * the success flag) when L2 exits (see nested_vmx_vmexit()).
+	 */
+	return 0;
+}
+
 /*
  * nested_vmx_run() handles a nested entry, i.e., a VMLAUNCH or VMRESUME on L1
  * for running an L2 nested guest.
@@ -10515,9 +10574,6 @@ 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;
 
@@ -10576,58 +10632,15 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	 * the nested entry.
 	 */
 
-	vmcs02 = nested_get_current_vmcs02(vmx);
-	if (!vmcs02)
-		return -ENOMEM;
-
-	enter_guest_mode(vcpu);
-
-	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
-		vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
-
-	cpu = get_cpu();
-	vmx->loaded_vmcs = vmcs02;
-	vmx_vcpu_put(vcpu);
-	vmx_vcpu_load(vcpu, cpu);
-	vcpu->cpu = cpu;
-	put_cpu();
-
-	vmx_segment_cache_clear(vmx);
-
-	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_qual);
-		return 1;
-	}
-
-	nested_get_vmcs12_pages(vcpu, vmcs12);
-
-	msr_entry_idx = nested_vmx_load_msr(vcpu,
-					    vmcs12->vm_entry_msr_load_addr,
-					    vmcs12->vm_entry_msr_load_count);
-	if (msr_entry_idx) {
-		leave_guest_mode(vcpu);
-		vmx_load_vmcs01(vcpu);
-		nested_vmx_entry_failure(vcpu, vmcs12,
-				EXIT_REASON_MSR_LOAD_FAIL, msr_entry_idx);
-		return 1;
-	}
-
-	vmcs12->launch_state = 1;
+	ret = enter_vmx_non_root_mode(vcpu, true);
+	if (ret)
+		return ret;
 
 	if (vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT)
 		return kvm_vcpu_halt(vcpu);
 
 	vmx->nested.nested_run_pending = 1;
 
-	/*
-	 * Note no nested_vmx_succeed or nested_vmx_fail here. At this point
-	 * we are no longer running L1, and VMLAUNCH/VMRESUME has not yet
-	 * returned as far as L1 is concerned. It will only return (and set
-	 * the success flag) when L2 exits (see nested_vmx_vmexit()).
-	 */
 	return 1;
 
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