linux-kernel - [PATCH v2 20/22] KVM: VMX: Use vmx_interrupt_blocked() directly from vmx_handle

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Date:   Sat, 25 Apr 2020 03:02:13 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     wei.huang2@....com, cavery@...hat.com, vkuznets@...hat.com,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Oliver Upton <oupton@...gle.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v2 20/22] KVM: VMX: Use vmx_interrupt_blocked() directly from vmx_handle_exit()

From: Sean Christopherson <sean.j.christopherson@...el.com>

Use vmx_interrupt_blocked() instead of bouncing through
vmx_interrupt_allowed() when handling edge cases in vmx_handle_exit().
The nested_run_pending check in vmx_interrupt_allowed() should never
evaluate true in the VM-Exit path.

Hoist the WARN in handle_invalid_guest_state() up to vmx_handle_exit()
to enforce the above assumption for the !enable_vnmi case, and to detect
any other potential bugs with nested VM-Enter.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Message-Id: <20200423022550.15113-12-sean.j.christopherson@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 7fb7dcb3d94d..0e5eacd6f911 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5268,18 +5268,11 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 	bool intr_window_requested;
 	unsigned count = 130;
 
-	/*
-	 * We should never reach the point where we are emulating L2
-	 * due to invalid guest state as that means we incorrectly
-	 * allowed a nested VMEntry with an invalid vmcs12.
-	 */
-	WARN_ON_ONCE(vmx->emulation_required && vmx->nested.nested_run_pending);
-
 	intr_window_requested = exec_controls_get(vmx) &
 				CPU_BASED_INTR_WINDOW_EXITING;
 
 	while (vmx->emulation_required && count-- != 0) {
-		if (intr_window_requested && vmx_interrupt_allowed(vcpu))
+		if (intr_window_requested && !vmx_interrupt_blocked(vcpu))
 			return handle_interrupt_window(&vmx->vcpu);
 
 		if (kvm_test_request(KVM_REQ_EVENT, vcpu))
@@ -5896,6 +5889,14 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
 	if (enable_pml)
 		vmx_flush_pml_buffer(vcpu);
 
+	/*
+	 * We should never reach this point with a pending nested VM-Enter, and
+	 * more specifically emulation of L2 due to invalid guest state (see
+	 * below) should never happen as that means we incorrectly allowed a
+	 * nested VM-Enter with an invalid vmcs12.
+	 */
+	WARN_ON_ONCE(vmx->nested.nested_run_pending);
+
 	/* If guest state is invalid, start emulating */
 	if (vmx->emulation_required)
 		return handle_invalid_guest_state(vcpu);
@@ -5962,7 +5963,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu,
 
 	if (unlikely(!enable_vnmi &&
 		     vmx->loaded_vmcs->soft_vnmi_blocked)) {
-		if (vmx_interrupt_allowed(vcpu)) {
+		if (!vmx_interrupt_blocked(vcpu)) {
 			vmx->loaded_vmcs->soft_vnmi_blocked = 0;
 		} else if (vmx->loaded_vmcs->vnmi_blocked_time > 1000000000LL &&
 			   vcpu->arch.nmi_pending) {
-- 
2.18.2