On Thu, Sep 15, 2016 at 02:51:59PM +0200, Lluís Vilanova wrote: > Stefan Hajnoczi writes: > > > On Wed, Sep 14, 2016 at 06:01:17PM +0200, Lluís Vilanova wrote: > >> Stefan Hajnoczi writes: > >> > >> > On Tue, Sep 06, 2016 at 04:25:53PM +0200, Lluís Vilanova wrote: > >> >> +## vCPU > >> >> + > >> >> +# Create a new virtual (guest) CPU > >> >> +# > >> >> +# Targets: all > >> >> +guest_cpu_init(void *cpu) "cpu=%p" > >> > >> > This isn't a vcpu trace event. Please add keep it with the other > >> > non-vcpu trace events: > >> > >> > # cpus.c > >> > guest_cpu_init(void *cpu) "cpu=%p" > >> > >> It actually is, but as the commit message says, declaring it as such > >> prevents > >> the event to be emitted. > > > If it cannot be toggled on a per-vcpu basis then claiming it's a vcpu > > event doesn't make sense. > > >> The culprit of this problem is that new vCPUs start with an empty per-vCPU > >> trace > >> event set. Should we make vCPUs "inherit" the state from the global state? > >> (i.e., if any vcpu event is set on any vCPU, set it on the new one). The > >> next > >> question would then be, should this inheritance only apply until tracing is > >> fully initialized of for the whole duration of QEMU? > > > I think the underlying issue is that trace_init_vcpu_events() assumes > > there is a single instant where vcpus all exist and need to be > > initialized. > > > A model that supports vcpu hotplug is really needed. In that model the > > global dstate should be the "global" state that determines whether vcpus > > are initialized with the event enabled or disabled. > > Ok, so then you're going for what I was saying. "Inheriting" the state of > every > new vCPU from the global dynamic state. If *any* vCPU has an event enabled, > all > new vCPUs will too.
No, I was thinking of something slightly different: Right now vcpu trace events use the global dstate during intialization only. After trace_init_vcpu_events() their dstate is zeroed. What if we leave the global dstate and use it as the template for enabling events in new vCPUs (hotplugged or static)? > As I said, next question is whether inheritance should apply only until full > initialization, or the whole time. I thing the latter is less confusing. I agree that it should apply the whole time.
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