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. Given the increasingly complex logic, and the nicer code if the new "if" is placed last, opportunistically change the "||" into a chain of "if (...) return false" statements. Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> --- arch/x86/kvm/x86.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 99a58c25f5c2..b912eef5dc1a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -12270,14 +12270,28 @@ 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 (!kvm_pv_async_pf_enabled(vcpu)) return false; - if (!kvm_pv_async_pf_enabled(vcpu) || - (vcpu->arch.apf.send_user_only && static_call(kvm_x86_get_cpl)(vcpu) == 0)) + if (vcpu->arch.apf.send_user_only && + static_call(kvm_x86_get_cpl)(vcpu) == 0) return false; - return true; + if (is_guest_mode(vcpu)) { + /* + * L1 needs to opt into the special #PF vmexits that are + * used to deliver async page faults. + */ + return vcpu->arch.apf.delivery_as_pf_vmexit; + } else { + /* + * Play it safe in case the guest does a quick real mode + * foray. The real mode IDT is unlikely to have a #PF + * exception setup. + */ + return is_paging(vcpu); + } } bool kvm_can_do_async_pf(struct kvm_vcpu *vcpu) -- 2.31.1