On Thu, May 03, 2018 at 01:50:39PM +0200, Paolo Bonzini wrote: > On 03/05/2018 13:32, Alexander Shishkin wrote: > >> > >> +/* Default is SYSTEM mode. */ > >> +static int __read_mostly pt_mode = PT_MODE_SYSTEM; > >> +module_param(pt_mode, int, S_IRUGO); > > So, it's an explicit module parameter? One apparent problem with this > > is that one would need to reload kvm module(s) to be able to use PT, > > which is not ideal. > > If you want to do tracing system-wide, that by definition must disable > guest tracing,
Sure. > so I think the module parameter is appropriate. I don't see why. System-wide tracing takes place while perf record is running. When it's done, it's done and we can un-disable the guest tracing, without requiring the user to kill all their VMs and reload modules. Regards, -- Alex
