From: Andi Kleen <andi@firstfloor.org>
To: Stephane Eranian <eranian@google.com>
Cc: David Ahern <dsahern@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Gleb Natapov <gleb@redhat.com>, Avi Kivity <avi@redhat.com>
Subject: Re: perf, x86: only do lbr init if bts is available
Date: Fri, 25 May 2012 15:49:04 -0700 [thread overview]
Message-ID: <m2obpblvvj.fsf@firstfloor.org> (raw)
In-Reply-To: <CABPqkBQc=XAfGY8_Rex4Hy91eBtwxtGzpfT0RaskBDDcSv1C4w@mail.gmail.com> (Stephane Eranian's message of "Thu, 24 May 2012 19:11:28 +0200")
Stephane Eranian <eranian@google.com> writes:
> On Thu, May 24, 2012 at 6:41 PM, David Ahern <dsahern@gmail.com> wrote:
>> On 5/24/12 10:35 AM, Stephane Eranian wrote:
>>>
>>> Well, no. There is no connection between BTS and LBR and you're creating
>>> one.
>>
>>
>> Ok. That was not clear to me from skimming the manual.
>> Then should it be tied to X86_FEATURE_DTES64?
>>
> No, it is unrelated to the Debug Store.
> There is really nothing you can use to figure that out, not event IA32_DEBUGCTL.
One way to do it would be to reread DEBUGCTL after writing and see if
the bit really changed to 1. If not assume LBR is not available.
-Andi
--
ak@linux.intel.com -- Speaking for myself only
next prev parent reply other threads:[~2012-05-25 22:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-24 16:19 perf, x86: only do lbr init if bts is available David Ahern
2012-05-24 16:35 ` Stephane Eranian
2012-05-24 16:41 ` David Ahern
2012-05-24 17:07 ` David Ahern
2012-05-24 17:11 ` Stephane Eranian
2012-05-25 22:49 ` Andi Kleen [this message]
2012-05-24 17:18 ` Peter Zijlstra
2012-05-24 17:21 ` Peter Zijlstra
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