Re: [PATCH 5/6] KVM: x86: never clear irr_pending in kvm_apic_update_apicv
From: Paolo Bonzini
Date: Fri Dec 10 2021 - 08:03:24 EST
On 12/10/21 13:47, Maxim Levitsky wrote:
If we scan vIRR here and see no bits, and*then* disable AVIC,
there is a window where the they could legit be turned on without any cpu errata,
and we will not have irr_pending == true, and thus the following
KVM_REQ_EVENT will make no difference.
Right.
Not touching irr_pending and letting just the KVM_REQ_EVENT do the work
will work too,
Yeah, I think that's preferrable. irr_pending == true is a conservative
setting that works; irr_pending will be evaluated again on the first
call to apic_clear_irr and that's enough.
With that justification, you don't need to reorder the call to
kvm_apic_update_apicv to be after kvm_x86_refresh_apicv_exec_ctrl.
Paolo
and if the avic errata is present, reduce slightly
the chances of it happening.