On Tue, Feb 14, 2017 at 07:21:34PM +0200, Alexander Shishkin wrote: > Peter Zijlstra <pet...@infradead.org> writes: > > > On Tue, Feb 14, 2017 at 06:17:30PM +0200, Alexander Shishkin wrote: > >> This is called by pmu::add(), which checks hw.state afterwards and if it > >> finds HES_STOPPED, it returns an error, which event_sched_in() captures > >> and keeps the event in INACTIVE state. Should I add a comment about it? > > > > Egads... so what if ->add() succeeds but we then hit this on > > ->stop()/->start() due to throttle or period adjust? > > It will hang there with hw.state==PERF_HES_STOPPED till the next > sched_out. But that will be the case anyway if VMXON kicks in while PT > is running.
Right, so I question the whole 'lets not schedule PT when VMX' premise, it leads to inconsistencies all over. How about we treat it like ->add() succeeded and VMX simply results in no output. Esp. when you then emit 'fake' data into/from a vmlaunch/vmresume instruction.
