linux-kernel - Re: [PATCH 1/2] perf x86: Make intel_pmu_enable

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:	Mon, 19 Aug 2013 16:31:31 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH 1/2] perf x86: Make intel_pmu_enable_all to enable only
 active events

Hi,

On Mon, Aug 19, 2013 at 1:16 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Mon, Aug 19, 2013 at 11:16:54AM +0200, Stephane Eranian wrote:
>> On Thu, Aug 15, 2013 at 3:53 PM, Andi Kleen <andi@...stfloor.org> wrote:
>> >>
>> >> I think its a NOP; this is the global ctrl register but
>> >> intel_pmu_disable_event() writes PERFEVTSELx.EN = 0, so even if you
>> >> enable it in the global mask, the event should still be disabled.
>> >
>> > Yes the hardware ANDs the various enable bits in the different
>> > registers.
>> >
>> Andi is correct. There is a logical AND between GLOBAL_CTRL and
>> the individual PERFEVTCTL.EN bits. If the EN bit is zero, then the
>> counter does not count. That also applies to fixed counters.
>
> right, peter mentioned I could have seen already queded
> NMI comming in for that event..
>
Yeah, I think you can have one NMI pending because it came
while you were already servicing an NMI interrupt. Though, this
is very unlikely.
--
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/