From: Borislav Petkov <bp@alien8.de>
To: "Luck, Tony" <tony.luck@intel.com>
Cc: x86@kernel.org, Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Darren Hart <dvhart@infradead.org>,
Andy Lutomirski <luto@kernel.org>,
linux-kernel@vger.kernel.org, linux-edac@vger.kernel.org,
linux-mm@kvack.org
Subject: Re: [PATCH v5] x86/mce: Avoid infinite loop for copy from user recovery
Date: Tue, 2 Feb 2021 12:01:26 +0100 [thread overview]
Message-ID: <20210202110126.GB18075@zn.tnic> (raw)
In-Reply-To: <20210201185812.GA54867@agluck-desk2.amr.corp.intel.com>
On Mon, Feb 01, 2021 at 10:58:12AM -0800, Luck, Tony wrote:
> On Thu, Jan 28, 2021 at 06:57:35PM +0100, Borislav Petkov wrote:
> > Crazy idea: if you still can reproduce on -rc3, you could bisect: i.e.,
> > if you apply the patch on -rc3 and it explodes and if you apply the same
> > patch on -rc5 and it works, then that could be a start... Yeah, don't
> > have a better idea here. :-\
>
> I tried reporoducing (applied the original patch I posted back to -rc3) and
> the same issue stubbornly refused to show up again.
>
> But I did hit something with the same signature (overflow bit set in
> bank 1) while running my futex test (which has two processes mapping
> the poison page). This time I *do* understand what happened. The test
> failed when the two processes were running on the two hyperhtreads of
> the same core. Seeing overflow in this case is understandable because
> bank 1 MSRs on my test machine are shared between the HT threads. When
> I run the test again using taskset(1) to only allowing running on
> thread 0 of each core, it keeps going for hunderds of iterations.
>
> I'm not sure I can stitch together how this overflow also happened for
> my single process test. Maybe a migration from one HT thread to the
> other at an awkward moment?
Sounds plausible.
And the much more important question is, what is the code supposed to
do when that overflow *actually* happens in real life? Because IINM,
an overflow condition on the same page would mean killing the task to
contain the error and not killing the machine...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2021-02-02 11:02 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-08 22:22 [PATCH 0/2] Fix infinite machine check loop in futex_wait_setup() Tony Luck
2021-01-08 22:22 ` [PATCH 1/2] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-08 22:22 ` [PATCH 2/2] futex, x86/mce: Avoid double machine checks Tony Luck
2021-01-08 22:47 ` Peter Zijlstra
2021-01-08 23:08 ` Luck, Tony
2021-01-08 23:14 ` Peter Zijlstra
2021-01-08 23:20 ` Luck, Tony
2021-01-11 21:44 ` [PATCH v2 0/3] Fix infinite machine check loop in futex_wait_setup() Tony Luck
2021-01-11 21:44 ` [PATCH v2 1/3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-11 22:11 ` Andy Lutomirski
2021-01-11 22:20 ` Luck, Tony
2021-01-12 17:00 ` Andy Lutomirski
2021-01-12 17:16 ` Luck, Tony
2021-01-12 17:21 ` Andy Lutomirski
2021-01-12 18:23 ` Luck, Tony
2021-01-12 18:57 ` Andy Lutomirski
2021-01-12 20:52 ` Luck, Tony
2021-01-12 22:04 ` Andy Lutomirski
2021-01-13 1:50 ` Luck, Tony
2021-01-13 4:15 ` Andy Lutomirski
2021-01-13 10:00 ` Borislav Petkov
2021-01-13 16:06 ` Luck, Tony
2021-01-13 16:19 ` Borislav Petkov
2021-01-13 16:32 ` Luck, Tony
2021-01-13 17:35 ` Borislav Petkov
2021-01-14 20:22 ` Borislav Petkov
2021-01-14 21:05 ` Luck, Tony
2021-01-11 21:44 ` [PATCH v2 2/3] x86/mce: Add new return value to get_user() for machine check Tony Luck
2021-01-11 21:44 ` [PATCH v2 3/3] futex, x86/mce: Avoid double machine checks Tony Luck
2021-01-14 17:22 ` [PATCH v2 0/3] Fix infinite machine check loop in futex_wait_setup() Andy Lutomirski
2021-01-15 0:38 ` [PATCH v3] x86/mce: Avoid infinite loop for copy from user recovery Tony Luck
2021-01-15 15:27 ` Borislav Petkov
2021-01-15 19:34 ` Luck, Tony
2021-01-15 20:51 ` [PATCH v4] " Luck, Tony
2021-01-15 23:23 ` Luck, Tony
2021-01-19 10:56 ` Borislav Petkov
2021-01-19 23:57 ` Luck, Tony
2021-01-20 12:18 ` Borislav Petkov
2021-01-20 17:17 ` Luck, Tony
2021-01-21 21:09 ` Luck, Tony
2021-01-25 22:55 ` [PATCH v5] " Luck, Tony
2021-01-26 11:03 ` Borislav Petkov
2021-01-26 22:36 ` Luck, Tony
2021-01-28 17:57 ` Borislav Petkov
2021-02-01 18:58 ` Luck, Tony
2021-02-02 11:01 ` Borislav Petkov [this message]
2021-02-02 16:04 ` Luck, Tony
2021-02-02 21:06 ` Borislav Petkov
2021-02-02 22:12 ` Luck, Tony
2021-01-18 15:39 ` [PATCH v3] " Borislav Petkov
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