On Wed, Apr 05, 2017 at 08:29:12PM +0200, Paolo Bonzini wrote: > > > On 05/04/2017 19:45, Christoffer Dall wrote: > >>> But the problem is that kvm_make_all_cpus_request() only sends IPIs to > >>> CPUs where the mode was different from OUTSIDE_GUEST_MODE, so there it's > >>> about !OUTSIDE_GUEST_MODE rather than !IN_GUEST_MODE, so there's some > >>> subtlety here which I feel like it's dangerous to paper over. > >> Right, that needs fixing in the code. > > Really? I thought Paolo said that this is the intended behavior and > > semantics; non-urgent requests that should just be serviced before the > > next guest entry. > > Indeed, that's right... > > >> guest_mode is just an optimization that allows us to skip sending the > >> IPI when the VCPU is known to handle the request as soon as possible. > >> > >> IN_GUEST_MODE: we must force VM exit or the request could never be > >> handled > >> EXITING_GUEST_MODE: another request already forces the VM exit and > >> we're just waiting for the VCPU to notice our request > >> OUTSIDE_GUEST_MODE: KVM is going to notice our request without any > >> intervention > >> READING_SHADOW_PAGE_TABLES: same as OUTSIDE_GUEST_MODE -- rename to > >> unwieldly OUTSIDE_GUEST_MODE_READING_SHADOW_PAGE_TABLES? > > Again, I thought Paolo was arguing that EXITING_GUEST_MODE makes the > > whole thing work because you check that after checking requests? > > ... but apparently I was wrong here, see my email from this morning. > I now managed to understand that e-mail, so it feels like we're converging in our understanding, which I hope is a good thing - meaning that we're converging to a correct understanding :) -Christoffer
