Re: [tip:perf/core] perf/x86: Add an MSR PMU driver

Andy Lutomirski
2015-08-10T02:12:46Z

On Fri, Aug 7, 2015 at 1:34 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Thu, Aug 06, 2015 at 05:59:43PM +0200, Peter Zijlstra wrote:
>> On Thu, Aug 06, 2015 at 08:30:08AM -0700, Andy Lutomirski wrote:
>> > On Thu, Aug 6, 2015 at 8:21 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>> > > On Tue, Aug 04, 2015 at 08:39:27PM +0000, Liang, Kan wrote:
>> > > - default:
>> > > - err = -ENOTSUPP;
>> > > + if (!msr[i].test() || rdmsrl_safe(msr[i].msr, &val))
>> > > + msr[i].attr = NULL;
>> >
>> > IIRC rdmsrl_safe literally never fails under QEMU TCG, and I'm not
>>
>> *sigh* the borkage never stops does it :-(
>>
>> > entirely sure what happens under KVM if emulation kicks in. It might
>> > pay to keep the model check for the non-architectural stuff, or at
>> > least check for a nonzero return value.
>>
>> Of course, 0 might be a valid value.. Esp. for the SMI counter.
>
> This then..
>

LGTM on brief inspection.

--Andy