[PATCH v6 5/7] KVM: nVMX: Set VM-{Fail,Exit} failure info via params, not return val

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Convert all top-level nested VM-Enter consistency check functions to
use explicit parameters to pass failure information to the caller.
Using an explicit parameter achieves several goals:

  - Provides consistent prototypes for all functions.
  - Self-documents the net effect of failure, e.g. without the explicit
    parameter it may not be obvious that nested_vmx_check_guest_state()
    leads to a VM-Exit.
  - Does not give the false impression that failure information is
    always consumed and/or relevant, e.g. vmx_set_nested_state() only
    cares whether or not the checks were successful.

Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 arch/x86/kvm/vmx/nested.c | 61 ++++++++++++++++++++++-----------------
 1 file changed, 35 insertions(+), 26 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b22605d5ee9e..16cff40456ee 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -817,7 +817,8 @@ static int nested_vmx_store_msr_check(struct kvm_vcpu *vcpu,
  * Load guest's/host's msr at nested entry/exit.
  * return 0 for success, entry index for failure.
  */
-static u32 nested_vmx_load_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
+static int nested_vmx_load_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count,
+			       u32 *exit_reason, u32 *exit_qual)
 {
 	u32 i;
 	struct vmx_msr_entry e;
@@ -849,7 +850,9 @@ static u32 nested_vmx_load_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
 	}
 	return 0;
 fail:
-	return i + 1;
+	*exit_reason = EXIT_REASON_MSR_LOAD_FAIL;
+	*exit_qual = i + 1;
+	return -EINVAL;
 }
 
 static int nested_vmx_store_msr(struct kvm_vcpu *vcpu, u64 gpa, u32 count)
@@ -2574,12 +2577,15 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
 }
 
 static int nested_vmx_check_controls(struct kvm_vcpu *vcpu,
-				     struct vmcs12 *vmcs12)
+				     struct vmcs12 *vmcs12,
+				     u32 *vm_instruction_error)
 {
+	*vm_instruction_error = VMXERR_ENTRY_INVALID_CONTROL_FIELD;
+
 	if (nested_check_vm_execution_controls(vcpu, vmcs12) ||
 	    nested_check_vm_exit_controls(vcpu, vmcs12) ||
 	    nested_check_vm_entry_controls(vcpu, vmcs12))
-		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
+		return -EINVAL;
 
 	return 0;
 }
@@ -2624,10 +2630,13 @@ static int nested_check_host_control_regs(struct kvm_vcpu *vcpu,
 }
 
 static int nested_vmx_check_host_state(struct kvm_vcpu *vcpu,
-				       struct vmcs12 *vmcs12)
+				       struct vmcs12 *vmcs12,
+				       u32 *vm_instruction_error)
 {
+	*vm_instruction_error = VMXERR_ENTRY_INVALID_HOST_STATE_FIELD;
+
 	if (nested_check_host_control_regs(vcpu, vmcs12))
-		return VMXERR_ENTRY_INVALID_HOST_STATE_FIELD;
+		return -EINVAL;
 
 	return 0;
 }
@@ -2673,10 +2682,12 @@ static int nested_check_guest_non_reg_state(struct vmcs12 *vmcs12)
 
 static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
 					struct vmcs12 *vmcs12,
+					u32 *exit_reason,
 					u32 *exit_qual)
 {
 	bool ia32e;
 
+	*exit_reason = EXIT_REASON_INVALID_STATE;
 	*exit_qual = ENTRY_FAIL_DEFAULT;
 
 	if (!nested_guest_cr0_valid(vcpu, vmcs12->guest_cr0) ||
@@ -2965,7 +2976,7 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
 	bool evaluate_pending_interrupts;
-	u32 exit_reason = EXIT_REASON_INVALID_STATE;
+	u32 exit_reason;
 	u32 exit_qual;
 
 	evaluate_pending_interrupts = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL) &
@@ -2991,7 +3002,8 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 			return -1;
 		}
 
-		if (nested_vmx_check_guest_state(vcpu, vmcs12, &exit_qual))
+		if (nested_vmx_check_guest_state(vcpu, vmcs12,
+						 &exit_reason, &exit_qual))
 			goto vmentry_fail_vmexit;
 	}
 
@@ -3003,11 +3015,9 @@ int nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu, bool from_vmentry)
 		goto vmentry_fail_vmexit_guest_mode;
 
 	if (from_vmentry) {
-		exit_reason = EXIT_REASON_MSR_LOAD_FAIL;
-		exit_qual = nested_vmx_load_msr(vcpu,
-						vmcs12->vm_entry_msr_load_addr,
-						vmcs12->vm_entry_msr_load_count);
-		if (exit_qual)
+		if (nested_vmx_load_msr(vcpu, vmcs12->vm_entry_msr_load_addr,
+					vmcs12->vm_entry_msr_load_count,
+					&exit_reason, &exit_qual))
 			goto vmentry_fail_vmexit_guest_mode;
 	} else {
 		/*
@@ -3087,6 +3097,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 	struct vmcs12 *vmcs12;
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	u32 interrupt_shadow = vmx_get_interrupt_shadow(vcpu);
+	u32 vm_instruction_error;
 	int ret;
 
 	if (!nested_vmx_check_permission(vcpu))
@@ -3136,13 +3147,11 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
 			launch ? VMXERR_VMLAUNCH_NONCLEAR_VMCS
 			       : VMXERR_VMRESUME_NONLAUNCHED_VMCS);
 
-	ret = nested_vmx_check_controls(vcpu, vmcs12);
-	if (ret)
-		return nested_vmx_failValid(vcpu, ret);
+	if (nested_vmx_check_controls(vcpu, vmcs12, &vm_instruction_error))
+		return nested_vmx_failValid(vcpu, vm_instruction_error);
 
-	ret = nested_vmx_check_host_state(vcpu, vmcs12);
-	if (ret)
-		return nested_vmx_failValid(vcpu, ret);
+	if (nested_vmx_check_host_state(vcpu, vmcs12, &vm_instruction_error))
+		return nested_vmx_failValid(vcpu, vm_instruction_error);
 
 	/*
 	 * We're finally done with prerequisite checking, and can start with
@@ -3594,7 +3603,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 				   struct vmcs12 *vmcs12)
 {
 	struct kvm_segment seg;
-	u32 entry_failure_code;
+	u32 ign;
 
 	if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER)
 		vcpu->arch.efer = vmcs12->host_ia32_efer;
@@ -3629,7 +3638,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 	 * Only PDPTE load can fail as the value of cr3 was checked on entry and
 	 * couldn't have changed.
 	 */
-	if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &entry_failure_code))
+	if (nested_vmx_load_cr3(vcpu, vmcs12->host_cr3, false, &ign))
 		nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
 
 	if (!enable_ept)
@@ -3727,7 +3736,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
 		vmx_update_msr_bitmap(vcpu);
 
 	if (nested_vmx_load_msr(vcpu, vmcs12->vm_exit_msr_load_addr,
-				vmcs12->vm_exit_msr_load_count))
+				vmcs12->vm_exit_msr_load_count, &ign, &ign))
 		nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_MSR_FAIL);
 }
 
@@ -5352,7 +5361,7 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	struct vmcs12 *vmcs12;
-	u32 exit_qual;
+	u32 ign;
 	int ret;
 
 	if (kvm_state->format != 0)
@@ -5465,9 +5474,9 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
 			return -EINVAL;
 	}
 
-	if (nested_vmx_check_controls(vcpu, vmcs12) ||
-	    nested_vmx_check_host_state(vcpu, vmcs12) ||
-	    nested_vmx_check_guest_state(vcpu, vmcs12, &exit_qual))
+	if (nested_vmx_check_controls(vcpu, vmcs12, &ign) ||
+	    nested_vmx_check_host_state(vcpu, vmcs12, &ign) ||
+	    nested_vmx_check_guest_state(vcpu, vmcs12, &ign, &ign))
 		return -EINVAL;
 
 	vmx->nested.dirty_vmcs12 = true;
-- 
2.21.0
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