linux-kernel - [PATCH 4.14 012/195] KVM MMU: check pending exception before injecting APF

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Date:   Thu, 15 Feb 2018 16:15:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ross Zwisler <zwisler@...il.com>,
        Alec Blayne <ab@...sa.net>,
        Haozhong Zhang <haozhong.zhang@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.14 012/195] KVM MMU: check pending exception before injecting APF

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Haozhong Zhang <haozhong.zhang@...el.com>

commit 2a266f23550be997d783f27e704b9b40c4010292 upstream.

For example, when two APF's for page ready happen after one exit and
the first one becomes pending, the second one will result in #DF.
Instead, just handle the second page fault synchronously.

Reported-by: Ross Zwisler <zwisler@...il.com>
Message-ID: <CAOxpaSUBf8QoOZQ1p4KfUp0jq76OKfGY4Uxs-Gg8ngReD99xww@...l.gmail.com>
Reported-by: Alec Blayne <ab@...sa.net>
Signed-off-by: Haozhong Zhang <haozhong.zhang@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/mmu.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3784,7 +3784,8 @@ static int kvm_arch_setup_async_pf(struc
 bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu)
 {
 	if (unlikely(!lapic_in_kernel(vcpu) ||
-		     kvm_event_needs_reinjection(vcpu)))
+		     kvm_event_needs_reinjection(vcpu) ||
+		     vcpu->arch.exception.pending))
 		return false;
 
 	if (!vcpu->arch.apf.delivery_as_pf_vmexit && is_guest_mode(vcpu))