linux-kernel - [PATCH v2 7/9] KVM: nVMX: Make an event request when pending an MTF nested VM-Exit

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Date:   Thu, 11 Aug 2022 17:06:03 -0400
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     seanjc@...gle.com, mlevitsk@...hat.com, vkuznets@...hat.com,
        stable@...r.kernel.org
Subject: [PATCH v2 7/9] KVM: nVMX: Make an event request when pending an MTF nested VM-Exit

From: Sean Christopherson <seanjc@...gle.com>

Set KVM_REQ_EVENT when MTF becomes pending to ensure that KVM will run
through inject_pending_event() and thus vmx_check_nested_events() prior
to re-entering the guest.

MTF currently works by virtue of KVM's hack that calls
kvm_check_nested_events() from kvm_vcpu_running(), but that hack will
be removed in the near future.  Until that call is removed, the patch
introduces no functional change.

Fixes: 5ef8acbdd687 ("KVM: nVMX: Emulate MTF when performing instruction emulation")
Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d7f8331d6f7e..940c0c0f8281 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1660,10 +1660,12 @@ static void vmx_update_emulated_instruction(struct kvm_vcpu *vcpu)
 	 */
 	if (nested_cpu_has_mtf(vmcs12) &&
 	    (!vcpu->arch.exception.pending ||
-	     vcpu->arch.exception.nr == DB_VECTOR))
+	     vcpu->arch.exception.nr == DB_VECTOR)) {
 		vmx->nested.mtf_pending = true;
-	else
+		kvm_make_request(KVM_REQ_EVENT, vcpu);
+	} else {
 		vmx->nested.mtf_pending = false;
+	}
 }
 
 static int vmx_skip_emulated_instruction(struct kvm_vcpu *vcpu)
-- 
2.31.1