KVM: nSVM: Clear EVENTINJ fields in vmcb12 on nested #VMEXIT

According to the APM, from the reference of the VMRUN instruction:

  Upon #VMEXIT, the processor performs the following actions in order to
  return to the host execution context:

  ...

  clear EVENTINJ field in VMCB

KVM already syncs EVENTINJ fields from vmcb02 to cached vmcb12 on every
L2->L0  #VMEXIT. Since these fields are zeroed by the CPU on #VMEXIT, they
will mostly be zeroed in vmcb12 on nested #VMEXIT by nested_svm_vmexit().

However, this is not the case when:

  1. Consistency checks fail, as nested_svm_vmexit() is not called.
  2. Entering guest mode fails before L2 runs (e.g. due to failed load of
     CR3).

(2) was broken by commit 2d8a42be0e2b ("KVM: nSVM: synchronize VMCB
controls updated by the processor on every vmexit"), as prior to that
nested_svm_vmexit() always zeroed EVENTINJ fields.

Explicitly clear the fields in all nested #VMEXIT code paths.

Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler")
Fixes: 2d8a42be0e2b ("KVM: nSVM: synchronize VMCB controls updated by the processor on every vmexit")
Cc: stable@vger.kernel.org
Signed-off-by: Yosry Ahmed <yosry@kernel.org>
Link: https://patch.msgid.link/20260303003421.2185681-12-yosry@kernel.org
[sean: massage changelog formatting]
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index ac7d7f82c82bd6eb3b30b4dcaa8be830f21e2920..90c8bc641bf321f89cd62d6e4c057931a76bf8bd 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1035,6 +1035,8 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
                vmcb12->control.exit_code    = SVM_EXIT_ERR;
                vmcb12->control.exit_info_1  = 0;
                vmcb12->control.exit_info_2  = 0;
+               vmcb12->control.event_inj = 0;
+               vmcb12->control.event_inj_err = 0;
                svm_set_gif(svm, false);
                goto out;
        }
@@ -1178,9 +1180,9 @@ static int nested_svm_vmexit_update_vmcb12(struct kvm_vcpu *vcpu)
        if (nested_vmcb12_has_lbrv(vcpu))
                svm_copy_lbrs(&vmcb12->save, &vmcb02->save);
 
+       vmcb12->control.event_inj         = 0;
+       vmcb12->control.event_inj_err     = 0;
        vmcb12->control.int_ctl           = svm->nested.ctl.int_ctl;
-       vmcb12->control.event_inj         = svm->nested.ctl.event_inj;
-       vmcb12->control.event_inj_err     = svm->nested.ctl.event_inj_err;
 
        trace_kvm_nested_vmexit_inject(vmcb12->control.exit_code,
                                       vmcb12->control.exit_info_1,