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From: Peter Zijlstra <peterz@infradead.org>
To: Stephane Eranian <eranian@google.com>
Cc: Ingo Molnar <mingo@kernel.org>, Jiri Olsa <jolsa@redhat.com>,
	LKML <linux-kernel@vger.kernel.org>,
	tonyj@suse.com, nelson.dsouza@intel.com
Subject: Re: [PATCH 1/8] perf/x86/intel: Fix memory corruption
Date: Wed, 20 Mar 2019 23:22:20 +0100	[thread overview]
Message-ID: <20190320222220.GA2490@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <CABPqkBQgmT+V29+eD6_rABzNBCo-R22N3PvPX4rWxSWEC0wPPg@mail.gmail.com>

On Wed, Mar 20, 2019 at 01:47:28PM -0700, Stephane Eranian wrote:

> Right now, if I do:
> 
> echo 0 > /sys/bus/event_source/devices/cpu/allow_tsx_force_abort
> 
> Then I don't have the guarantee on when there will be no abort when I
> return from the echo.  the MSR is accessed only on PMU scheduling. I
> would expect a sysadmin to want some guarantee if this is to be
> switched on/off at runtime. If not, then having a boot time option is
> better in my opinion.

Something like cycling the nmi watchdog or:

  perf stat -a -e cycles sleep 1

should be enough to force reschedule the events on every CPU.

Again, I'm not adverse to 'fixing' this if it can be done with limited
LoC. But I don't really see this as critical.

> This other bit I noticed is that cpuc->tfa_shadow is used to avoid the
> wrmsr(), but I don't see the code that makes sure the init value (0)
> matches the value of the MSR.  Is this MSR guarantee to be zero on
> reset? 

That was my understanding.

> How about on kexec()?

Good point, we might want to fix that.

  parent reply	other threads:[~2019-03-20 22:22 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-14 13:01 [RFC][PATCH 0/8] perf/x86: event scheduling cleanups Peter Zijlstra
2019-03-14 13:01 ` [PATCH 1/8] perf/x86/intel: Fix memory corruption Peter Zijlstra
2019-03-15 11:29   ` [tip:perf/urgent] " tip-bot for Peter Zijlstra
2019-03-19  6:29   ` [PATCH 1/8] " Stephane Eranian
2019-03-19 11:05     ` Peter Zijlstra
2019-03-19 17:52       ` Stephane Eranian
2019-03-19 18:20         ` Peter Zijlstra
2019-03-20 20:47           ` Stephane Eranian
2019-03-20 20:52             ` Stephane Eranian
2019-03-20 22:22             ` Peter Zijlstra [this message]
2019-03-21 12:38               ` Peter Zijlstra
2019-03-21 16:45                 ` Thomas Gleixner
2019-03-21 17:10                   ` Peter Zijlstra
2019-03-21 17:17                     ` Thomas Gleixner
2019-03-21 18:20                       ` Peter Zijlstra
2019-03-21 19:42                         ` Tony Jones
2019-03-21 19:47                           ` DSouza, Nelson
2019-03-21 20:07                             ` Peter Zijlstra
2019-03-21 23:16                               ` DSouza, Nelson
2019-03-22 22:14                                 ` DSouza, Nelson
2019-03-21 17:23                   ` Stephane Eranian
2019-03-21 17:51                     ` Thomas Gleixner
2019-03-22 19:04                       ` Stephane Eranian
2019-04-03  7:32                         ` Peter Zijlstra
2019-04-03 10:40                 ` [tip:perf/urgent] perf/x86/intel: Initialize TFA MSR tip-bot for Peter Zijlstra
2019-04-03 11:30                   ` Thomas Gleixner
2019-04-03 12:23                     ` Vince Weaver
2019-03-14 13:01 ` [RFC][PATCH 2/8] perf/x86/intel: Simplify intel_tfa_commit_scheduling() Peter Zijlstra
2019-03-14 13:01 ` [RFC][PATCH 3/8] perf/x86: Simplify x86_pmu.get_constraints() interface Peter Zijlstra
2019-03-19 21:21   ` Stephane Eranian
2019-03-14 13:01 ` [RFC][PATCH 4/8] perf/x86: Remove PERF_X86_EVENT_COMMITTED Peter Zijlstra
2019-03-19 20:48   ` Stephane Eranian
2019-03-19 21:00     ` Peter Zijlstra
2019-03-20 13:14       ` Peter Zijlstra
2019-03-20 12:23     ` Peter Zijlstra
2019-03-14 13:01 ` [RFC][PATCH 5/8] perf/x86/intel: Optimize intel_get_excl_constraints() Peter Zijlstra
2019-03-19 23:43   ` Stephane Eranian
2019-03-14 13:01 ` [RFC][PATCH 6/8] perf/x86: Clear ->event_constraint[] on put Peter Zijlstra
2019-03-19 21:50   ` Stephane Eranian
2019-03-20 12:25     ` Peter Zijlstra
2019-03-14 13:01 ` [RFC][PATCH 7/8] perf/x86: Optimize x86_schedule_events() Peter Zijlstra
2019-03-19 23:55   ` Stephane Eranian
2019-03-20 13:11     ` Peter Zijlstra
2019-03-20 19:30       ` Stephane Eranian
2019-03-14 13:01 ` [RFC][PATCH 8/8] perf/x86: Add sanity checks to x86_schedule_events() Peter Zijlstra
2019-03-15  7:15 ` [RFC][PATCH 0/8] perf/x86: event scheduling cleanups Stephane Eranian
2019-03-15  7:15   ` Stephane Eranian
2019-03-15  8:01     ` Peter Zijlstra

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