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

[Paolo Bonzini]

On 2/11/22 00:16, Sean Christopherson wrote:
> Third time's a charm...
>
> 	if (kvm_pv_async_pf_enabled(vcpu))
> 		return false;
>
> 	if (vcpu->arch.apf.send_user_only &&
> 	    static_call(kvm_x86_get_cpl)(vcpu) == 0)
> 		return false;
>
> 	/* L1 CR0.PG=1 is guaranteed if the vCPU is in guest mode (L2). */
> 	if (is_guest_mode(vcpu))
> 		return !vcpu->arch.apf.delivery_as_pf_vmexit;
>
> 	return is_paging(vcpu);

Went for this, but with slightly different final "if":

        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);
        }

Paolo