linux-kernel - [PATCH 2/3] KVM: nVMX: Leave most VM-Exit info fields unmodified on failed VM-Entry

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Message-Id: <20220407002315.78092-3-seanjc@google.com>
Date:   Thu,  7 Apr 2022 00:23:14 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Chenyi Qiang <chenyi.qiang@...el.com>
Subject: [PATCH 2/3] KVM: nVMX: Leave most VM-Exit info fields unmodified on
 failed VM-Entry

Don't modify vmcs12 exit fields except EXIT_REASON and EXIT_QUALIFICATION
when performing a nested VM-Exit due to failed VM-Entry.  Per the SDM,
only the two aformentioned fields are filled and "All other VM-exit
information fields are unmodified".

Fixes: 4704d0befb07 ("KVM: nVMX: Exiting from L2 to L1")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/nested.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index ec4cbf583921..9a4938955bad 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4198,12 +4198,12 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	if (to_vmx(vcpu)->exit_reason.enclave_mode)
 		vmcs12->vm_exit_reason |= VMX_EXIT_REASONS_SGX_ENCLAVE_MODE;
 	vmcs12->exit_qualification = exit_qualification;
-	vmcs12->vm_exit_intr_info = exit_intr_info;
-
-	vmcs12->idt_vectoring_info_field = 0;
-	vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
-	vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
 
+	/*
+	 * On VM-Exit due to a failed VM-Entry, the VMCS isn't marked launched
+	 * and only EXIT_REASON and EXIT_QUALIFICATION are updated, all other
+	 * exit info fields are unmodified.
+	 */
 	if (!(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) {
 		vmcs12->launch_state = 1;
 
@@ -4215,8 +4215,13 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 		 * Transfer the event that L0 or L1 may wanted to inject into
 		 * L2 to IDT_VECTORING_INFO_FIELD.
 		 */
+		vmcs12->idt_vectoring_info_field = 0;
 		vmcs12_save_pending_event(vcpu, vmcs12);
 
+		vmcs12->vm_exit_intr_info = exit_intr_info;
+		vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
+		vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
+
 		/*
 		 * According to spec, there's no need to store the guest's
 		 * MSRs if the exit is due to a VM-entry failure that occurs
-- 
2.35.1.1094.g7c7d902a7c-goog