linux-kernel - [PATCH 8/8] KVM: x86: drop KVM_PV_REASON_PAGE_READY case from kvm_handle_page

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Message-Id: <20200511164752.2158645-9-vkuznets@redhat.com>
Date:   Mon, 11 May 2020 18:47:52 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, x86@...nel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>,
        Vivek Goyal <vgoyal@...hat.com>, Gavin Shan <gshan@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 8/8] KVM: x86: drop KVM_PV_REASON_PAGE_READY case from kvm_handle_page_fault()

KVM guest code in Linux enables APF only when KVM_FEATURE_ASYNC_PF_INT
is supported, this means we will never see KVM_PV_REASON_PAGE_READY
when handling page fault vmexit in KVM.

While on it, make sure we only follow genuine page fault path when
APF reason is zero. If we happen to see something else this means
that the underlying hypervisor is misbehaving. Leave WARN_ON_ONCE()
to catch that.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/mmu/mmu.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8071952e9cf2..5a9fca908ca9 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4187,7 +4187,7 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
 
 	vcpu->arch.l1tf_flush_l1d = true;
 	switch (vcpu->arch.apf.host_apf_reason) {
-	default:
+	case 0:
 		trace_kvm_page_fault(fault_address, error_code);
 
 		if (kvm_event_needs_reinjection(vcpu))
@@ -4201,12 +4201,8 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
 		kvm_async_pf_task_wait(fault_address, 0);
 		local_irq_enable();
 		break;
-	case KVM_PV_REASON_PAGE_READY:
-		vcpu->arch.apf.host_apf_reason = 0;
-		local_irq_disable();
-		kvm_async_pf_task_wake(fault_address);
-		local_irq_enable();
-		break;
+	default:
+		WARN_ON_ONCE(1);
 	}
 	return r;
 }
-- 
2.25.4