linux-kernel - [PATCH 03/12] KVM: x86: do not deliver asynchronous page faults if CR0.PG=0

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Date:   Wed,  9 Feb 2022 12:00:11 -0500
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     vkuznets@...hat.com, mlevitsk@...hat.com, dmatlack@...gle.com,
        seanjc@...gle.com
Subject: [PATCH 03/12] KVM: x86: do not deliver asynchronous page faults if CR0.PG=0

Enabling async page faults is nonsensical if paging is disabled, but
it is allowed because CR0.PG=0 does not clear the async page fault
MSR.  Just ignore them and only use the artificial halt state,
similar to what happens in guest mode if async #PF vmexits are disabled.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/x86.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5e1298aef9e2..98aca0f2af12 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12272,7 +12272,9 @@ static inline bool apf_pageready_slot_free(struct kvm_vcpu *vcpu)
 
 static bool kvm_can_deliver_async_pf(struct kvm_vcpu *vcpu)
 {
-	if (!vcpu->arch.apf.delivery_as_pf_vmexit && is_guest_mode(vcpu))
+	if (is_guest_mode(vcpu)
+	    ? !vcpu->arch.apf.delivery_as_pf_vmexit
+	    : !is_cr0_pg(vcpu->arch.mmu))
 		return false;
 
 	if (!kvm_pv_async_pf_enabled(vcpu) ||
-- 
2.31.1