linux-kernel - Re: [PATCH v2 0/12] perf/x86: implement HT leak workaround for SNB/IVB/HSW

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]

Message-ID: <CABPqkBQuf_W1X_VbVzLhKbv6AZwKE3YyHGpT=cRFNBEak5wz_Q@mail.gmail.com>
Date:	Tue, 21 Oct 2014 15:08:32 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Jiri Olsa <jolsa@...hat.com>,
	"Liang, Kan" <kan.liang@...el.com>, Borislav Petkov <bp@...en8.de>,
	Maria Dimakopoulou <maria.n.dimakopoulou@...il.com>
Subject: Re: [PATCH v2 0/12] perf/x86: implement HT leak workaround for SNB/IVB/HSW

On Tue, Oct 21, 2014 at 3:03 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Oct 21, 2014 at 02:28:06PM +0200, Stephane Eranian wrote:
>> Peter,
>>
>> On Tue, Oct 21, 2014 at 1:25 PM, Peter Zijlstra <peterz@...radead.org> wrote:
>> >
>> >
>> > lkml.kernel.org/r/CABPqkBRbst4sgpgE5O_VXt-CSC0VD=aP2KWA0e3Uy64tw7df3A@...l.gmail.com
>> >
>> > I missed that 3 lines if they were in here.
>> >
>> I did not put them in there because there is another problem.
>> If you partition the generic counters 2 and 2, then some CPUs will not
>> be able to measure some events.
>> Unfortunately, there is no way to partition the 4 counters such that
>> all the events can be measured by
>> each CPU. Some events or precise sampling requires counter 2 for
>> instance (like prec_dist).
>> That's why I did not put this fix in.
>
> Ah, I wasn't thinking about a hard partition, just a limit on the number
> of exclusive counters any one CPU can claim such as to not starve. Or is
> that what you were talking about? I feel not being able to starve
> another CPU is more important than a better utilization bound for
> counter scheduling.

So you're saying, just limit number of used counters to 2 regardless
of which one
they are. So sometimes, this will avoid the problem aforementioned and sometimes
not. We can try that.
--
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/