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 <dgilbert@xxxxxxxxxx>
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d39d6cf1d473..44a86f7f2397 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2730,9 +2730,6 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
if (data & 0x30)
return 1;
- if (!lapic_in_kernel(vcpu))
- return 1;
-
vcpu->arch.apf.msr_en_val = data;
if (!kvm_pv_async_pf_enabled(vcpu)) {
@@ -2741,6 +2738,9 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
return 0;
}
+ if (!lapic_in_kernel(vcpu))
+ return 1;
+
if (kvm_gfn_to_hva_cache_init(vcpu->kvm, &vcpu->arch.apf.data, gpa,
sizeof(u64)))
return 1;
--
2.25.4
