[PATCH v6 17/31] KVM: nSVM: Clear EVENTINJ field in VMCB12 on nested #VMEXIT

[Yosry Ahmed <yosry@kernel.org>]

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 correctly cleared EVENTINJ (i.e. event_inj and event_inj_err) on
nested #VMEXIT before commit 2d8a42be0e2b ("KVM: nSVM: synchronize VMCB
controls updated by the processor on every vmexit"). That commit made
sure the fields are synchronized between VMCB02 and KVM's cached VMCB12
on every L2->L0 #VMEXIT, such that they are serialized correctly on
save/restore.

However, the commit also incorrectly copied the fields from KVM's cached
VMCB12 to L1's VMCB12 on nested #VMEXIT. This is mostly correct, as the
fields will be zeroed by the CPU, but it doesn't handle a #VMEXIT due to
an invalid VMRUN. Explicitly clear the fields all nested #VMEXIT code
paths.

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>
---
 arch/x86/kvm/svm/nested.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 2c5878cbb3940..dd95c6434403f 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -1027,6 +1027,8 @@ static void nested_svm_vmrun_error_vmexit(struct kvm_vcpu *vcpu, struct vmcb *vm
 	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;
 	__nested_svm_vmexit(svm);
 }
 
@@ -1199,9 +1201,9 @@ 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,
-- 
2.53.0.414.gf7e9f6c205-goog