linux-kernel - Re: [stable 4.19] [PANIC]: tracing: Centralize preemptirq tracepoints and unify their usage

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Message-ID: <20200925110706.6654954b@oasis.local.home>
Date:   Fri, 25 Sep 2020 11:07:06 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Naresh Kamboju <naresh.kamboju@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux- stable <stable@...r.kernel.org>,
        Sasha Levin <sashal@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        LTP List <ltp@...ts.linux.it>, lkft-triage@...ts.linaro.org
Subject: Re: [stable 4.19] [PANIC]: tracing: Centralize preemptirq
 tracepoints and unify their usage

On Fri, 25 Sep 2020 10:59:14 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Fri, 25 Sep 2020 10:54:58 -0400
> Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> 
> > The crash looks like its cr3 related, which I believe Peter Zijlstra  
> 
> s/cr3/cr2/
> 

Specifically, commits:

a0d14b8909de55139b8702fe0c7e80b69763dcfb ("x86/mm, tracing: Fix CR2 corruption")
6879298bd0673840cadd1fb36d7225485504ceb4 ("x86/entry/64: Prevent clobbering of saved CR2 value")
b8f70953c1251d8b16276995816a95639f598e70 ("x86/entry/32: Pass cr2 to do_async_page_fault()")

(which are in 5.4 but not 4.19)

But again, is this too intrusive. There was a workaround that was
original proposed, but Peter didn't want any more band-aids, and did
the restructuring, but as you can see from the two other patches, it
makes it a bit more high risk.

-- Steve