[PATCH v3 5/7] KVM: x86: VMX: synthesize invalid VM exit when emulating invalid guest state

From: Maxim Levitsky
Date: Mon Sep 13 2021 - 10:14:51 EST


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@xxxxxxxxxx>
Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
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 fada1055f325..57609dda1bbc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6618,10 +6618,21 @@ 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;
+ }

trace_kvm_entry(vcpu);

--
2.26.3