linux-kernel - Re: perf_counter Atom patch

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 23 Jun 2009 15:59:59 +0800
From:	Yong Wang <yong.y.wang@...ux.intel.com>
To:	eranian@...il.com
Cc:	"Wang, Yong Y" <yong.y.wang@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: perf_counter Atom patch

On Tue, Jun 23, 2009 at 09:45:03AM +0200, stephane eranian wrote:
>
> Unfortunately, I don't have a N270 to compare with your results.
> We need to verify whether or not N270 implements the fixed counters.
> Does it report architected perfmon v3 or v1?
> 

All Atom processors report perfmon v3 as specified in SDM. N270 is no
exception.

> > The return value of CPUID(0xa) is indeed bogus, too and there is another quirk for that in
> > intel_pmu_init() in arch/x86/kernel/cpu/perf_counter.c
> >
> > x86_pmu.num_counters_fixed ?? ?? ??= max((int)edx.split.num_counters_fixed, 3);
> >
> > Is this what you were talking about?
> 
> Not quite, because with the max() you'd have a problem on Intel Core
> Duo/Solo processors
> as they do implement the first generation of architected perfmon and
> that one did not have
> fixed counters. So you'd have to special case family=6 model=14.

That has been taken into account actually. Only perfmon v2 and above are
supported as you see in intel_pmu_init().

	if (version < 2)
		return -ENODEV;

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/