From d831de177217cd494bfb99f2c849a0d40c2a7890 Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Fri, 11 Sep 2020 11:31:47 +0200 Subject: [PATCH] KVM: x86: always allow writing '0' to MSR_KVM_ASYNC_PF_EN Even without in-kernel LAPIC we should allow writing '0' to MSR_KVM_ASYNC_PF_EN as we're not enabling the mechanism. In particular, QEMU with 'kernel-irqchip=off' fails to start a guest with qemu-system-x86_64: error: failed to set MSR 0x4b564d02 to 0x0 Fixes: 9d3c447c72fb2 ("KVM: X86: Fix async pf caused null-ptr-deref") Reported-by: Dr. David Alan Gilbert Signed-off-by: Vitaly Kuznetsov Message-Id: <20200911093147.484565-1-vkuznets@redhat.com> [Actually commit the version proposed by Sean Christopherson. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 432ef34..e3de0fe 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2735,7 +2735,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data) return 1; if (!lapic_in_kernel(vcpu)) - return 1; + return data ? 1 : 0; vcpu->arch.apf.msr_en_val = data; -- 2.7.4