Re: [RFC PATCH v2 2/3] perf/x86/intel/pt: Introduce and export pt_get_curr_event()

[Peter Zijlstra]

On Thu, Sep 22, 2022 at 01:59:53PM +0000, Wang, Wei W wrote:
> On Thursday, September 22, 2022 9:35 PM, Peter Zijlstra
> > On Thu, Sep 22, 2022 at 12:58:49PM +0000, Wang, Wei W wrote:
> > 
> > > Add a function to expose the current running PT event to users. One
> > > usage is in KVM, it needs to get and disable the running host PT event
> > > before VMEnter to the guest and resumes the event after VMexit to host.
> > 
> > You cannot just kill a host event like that. If there is a host event, the guest
> > looses out.
> 
> OK. The intention was to pause the event (that only profiles host info) when switching to guest,
> and resume when switching back to host.

If the even doesn't profile guest context, then yes. If it does profile
guest context, you can't.