On Fri, Jun 09, 2017 at 09:29:45AM +0200, Paolo Bonzini wrote: > > > On 09/06/2017 04:50, Peter Xu wrote: > > Even, I'm thinking whether we can unconditionally setup PDST only in > > pi_load(), then post_block() only needs to handle the NV bit. > > No, you can't do that without fiddling with the blocked_vcpu lists in > pi_load. Then how about we keep the blocked_vcpu list maintainance in post_block(), but only let pi_load() handle the PDST? (I really feel like they are two things - the blocked_vcpu list helps for the kick when wakeup happens; while PDST makes sure the PI is always pointing to the correct cpu) > > > (PS. since I'm at here... could I ask why in pi_pre_block we need to > > udpate PDST as well? I guess that decides who will run the > > wakeup_handler code to kick the vcpu thread, but would that really > > matter?) > > For this one it's a yes. :) I think it's not needed anymore indeed > after these patches; see this comment: > > /* > * The wakeup_handler expects the VCPU to be on the > * blocked_vcpu_list that matches ndst. Actually I was always unclear on what this sentense means: iiuc blocked_vcpu_list is only a list of vcpus that may need a kick, so why it has anything to do with PDST after all? (or say, no matter what PDST is, we just kick the vcpu thread without doing anything else, do we?) > Interrupts > * are disabled so no preemption should happen, but > * err on the side of safety. > */ > > So we could add a WARN. Thanks, -- Peter Xu
