linux-kernel - [PATCH MANUALSEL 5.10 4/7] KVM: x86: VMX: synthesize invalid VM exit when emulating invalid guest state

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Date:   Wed,  6 Oct 2021 07:12:30 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Maxim Levitsky <mlevitsk@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, kvm@...r.kernel.org
Subject: [PATCH MANUALSEL 5.10 4/7] KVM: x86: VMX: synthesize invalid VM exit when emulating invalid guest state

From: Maxim Levitsky <mlevitsk@...hat.com>

[ Upstream commit c42dec148b3e1a88835e275b675e5155f99abd43 ]

Since no actual VM entry happened, the VM exit information is stale.
To avoid this, synthesize an invalid VM guest state VM exit.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
Message-Id: <20210913140954.165665-6-mlevitsk@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/vmx/vmx.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index fcd8bcb7e0ea..e3af56f05a37 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6670,10 +6670,21 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
 		     vmx->loaded_vmcs->soft_vnmi_blocked))
 		vmx->loaded_vmcs->entry_time = ktime_get();
 
-	/* Don't enter VMX if guest state is invalid, let the exit handler
-	   start emulation until we arrive back to a valid state */
-	if (vmx->emulation_required)
+	/*
+	 * Don't enter VMX if guest state is invalid, let the exit handler
+	 * start emulation until we arrive back to a valid state.  Synthesize a
+	 * consistency check VM-Exit due to invalid guest state and bail.
+	 */
+	if (unlikely(vmx->emulation_required)) {
+		vmx->fail = 0;
+		vmx->exit_reason.full = EXIT_REASON_INVALID_STATE;
+		vmx->exit_reason.failed_vmentry = 1;
+		kvm_register_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_1);
+		vmx->exit_qualification = ENTRY_FAIL_DEFAULT;
+		kvm_register_mark_available(vcpu, VCPU_EXREG_EXIT_INFO_2);
+		vmx->exit_intr_info = 0;
 		return EXIT_FASTPATH_NONE;
+	}
 
 	if (vmx->ple_window_dirty) {
 		vmx->ple_window_dirty = false;
-- 
2.33.0