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Date: Thu, 2 Jun 2016 09:07:04 -0700
From: Andi Kleen <ak@linux.intel.com>
To: David Carrillo-Cisneros <davidcc@google.com>
Cc: linux-kernel@vger.kernel.org, "x86@kernel.org" <x86@kernel.org>,
        Ingo Molnar <mingo@redhat.com>, "Yan, Zheng" <zheng.z.yan@intel.com>,
        Kan Liang <kan.liang@intel.com>, Peter Zijlstra <peterz@infradead.org>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 2/3] perf/x86/intel: fix for MSR_LAST_BRANCH_FROM_x quirk
 when no TSX
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>   $ ./lbr_perf record --call-graph lbr -e cycles:k ./cqm_easy
> 
> where lbr_perf is the patched perf tool, that allows to specify :k
> on lbr mode. The above command will trigger a #GPF :

Why would you want to do that? We usually have frame pointers for
the kernel, so callstack LBR for the kernel is pointless.

-Andi