Hey, On Tue, Aug 21, 2018 at 04:59:08PM -0700, Andi Kleen wrote: > On Tue, Aug 21, 2018 at 04:05:22PM -0700, Eduardo Valentin wrote: > > On Tue, Aug 21, 2018 at 03:09:37PM -0700, Andi Kleen wrote: > > > On Tue, Aug 21, 2018 at 02:15:28PM -0700, Eduardo Valentin wrote: > > > > On a system with X86_FEATURE_ARCH_PERFMON disabled > > > > and with a model not known by family PMU drivers, > > > > user gets a kernel message log like the following: > > > > [ 0.100114] Performance Events: unsupported p6 CPU model 85 no PMU > > > > driver, software events only. > > > > > > > > The "unsupported .. CPU" part may be confusing for some > > > > users. Rewording the messages on the failure path to: > > > > [ 0.667154] Performance Events: unknown p6 PMU on CPU model 85: > > > > !X86_FEATURE_ARCH_PERFMON: no PMU driver, software events only. > > > > > > Are you sure users even know what ARCH_PERFMON is? > > > > > > Maybe it is confusing (why exactly?), but it doesn't seem to me that your > > > new message is any better. > > > > Yeah, the part that says "unsupported CPU" is the confusing part, > > That makes sense. > > > I get people thinking that the specific reported CPU model is not > > supported by the kernel :-) > > > > > > > > If you refer to VMs not exposing the PMU perhaps that should be > > > explicitely mentioned. > > > > > > Of course the real fix is to always expose the PMU, not improve the error > > > messages... > > > > I agree that best is simply to enable PMU. But it does not hurt to improve > > the error messaging, does it? > > > > Any suggestions there, given that the initial attempt seams to make it even > > worse :-) > > Perhaps just say > > "CPU does not support PMU" >
Ok. > which is really what the problem is here. > Fair enough. > The other option would be to move this message after the big model switch, > but would need to be very careful that it doesn't have any unintended > side effects. I will simply remove those messages with CPU model details and on the failure path build the message to look like: [ 0.666785] Performance Events: CPU does not support PMU: no PMU driver, software events only. > > -Andi > -- All the best, Eduardo Valentin
