From: Peter Zijlstra <peterz@infradead.org>
To: "Liang, Kan" <kan.liang@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>
Subject: Re: [PATCH V2 2/3] perf protect LBR when Intel PT is enabled.
Date: Mon, 7 Jul 2014 17:46:35 +0200 [thread overview]
Message-ID: <20140707154635.GG19379@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <37D7C6CF3E00A74B8858931C1DB2F077014C6431@SHSMSX103.ccr.corp.intel.com>
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On Mon, Jul 07, 2014 at 01:57:16PM +0000, Liang, Kan wrote:
> > > This doesn't work, e.g. hardware debuggers can take over at any time.
> >
> > Tough cookies. Hardware debuggers get to deal with whatever crap they
> > cause.
>
> If so, I think I may discard this patch (2/3). I will resubmit the
> other two patches as a patch set to only handle the KVM issue we
> found. It checks the access of LBR and extra MSRs at the
> initialization time and set the flags. So we just need to check the
> flags at runtime and avoid the protection by _safe().
Right.
> For Intel PT and LBR handling, since the PT codes haven't been
> integrated yet, I will try to implement another patch later. The
> patch will add flags for LBR and PT. When enabling PT, it checks LBR
> flag and update the PT flag. When enabling LBR, it checks PT flag and
> update the LBR flag. When disabling LBR/PT, we just update the related
> flags. we don't need to add _safe or extra rmsr in fast path.
Yeah, should be part of the PT patches.
> How do you think?
With my brain, much like all primates :-)
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next prev parent reply other threads:[~2014-07-07 15:46 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-02 18:14 [PATCH V2 1/3] perf ignore LBR and offcore_rsp kan.liang
2014-07-02 18:14 ` [PATCH V2 2/3] perf protect LBR when Intel PT is enabled kan.liang
2014-07-03 2:44 ` Andi Kleen
2014-07-03 7:33 ` Peter Zijlstra
2014-07-03 15:52 ` Andi Kleen
2014-07-03 17:07 ` Peter Zijlstra
2014-07-07 13:57 ` Liang, Kan
2014-07-07 15:46 ` Peter Zijlstra [this message]
2014-07-07 15:47 ` Peter Zijlstra
2014-07-02 18:14 ` [PATCH V2 3/3] kvm: ignore LBR and offcore rsp kan.liang
2014-07-03 2:16 ` [PATCH V2 1/3] perf ignore LBR and offcore_rsp Andi Kleen
2014-07-03 4:26 ` Liang, Kan
2014-07-03 2:29 ` Jidong Xiao
2014-07-03 4:26 ` Liang, Kan
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