From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "Luck, Tony" <tony.luck@intel.com>,
Prarit Bhargava <prarit@redhat.com>,
Vivek Goyal <vgoyal@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Junichi Nomura <j-nomura@ce.jp.nec.com>,
Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Subject: Re: [PATCH v6] x86: mce: kexec: switch MCE handler for kexec/kdump
Date: Fri, 6 Mar 2015 09:09:30 +0000 [thread overview]
Message-ID: <20150306090930.GA14982@hori1.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20150306083421.GD3514@pd.tnic>
On Fri, Mar 06, 2015 at 09:34:21AM +0100, Borislav Petkov wrote:
> On Fri, Mar 06, 2015 at 02:59:13AM +0000, Naoya Horiguchi wrote:
> > From 8890e9976c525a4b480bf5f86008641688de8c11 Mon Sep 17 00:00:00 2001
> > From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > Date: Fri, 6 Mar 2015 11:52:10 +0900
> > Subject: [PATCH v6] x86: mce: kexec: switch MCE handler for kexec/kdump
> >
> > kexec disables (or "shoots down") all CPUs other than a crashing CPU before
> > entering the 2nd kernel. But the MCE handler is still enabled after that,
> > so if MCE happens and broadcasts over the CPUs after the main thread starts
> > the 2nd kernel (which might not initialize MCE device yet, or might decide
> > not to enable it,) MCE handler runs only on the other CPUs (not on the main
> > thread,) leading to kernel panic with MCE synchronization. The user-visible
> > effect of this bug is kdump failure.
> >
> > Our standard MCE handler do_machine_check() assumes some about system's
> > status and it's hard to alter it to cover kexec/kdump context, so let's add
> > another kdump-specific one and switch to it.
> >
> > Note that this problem exists since current MCE handler was implemented in
> > 2.6.32, and recently commit 716079f66eac ("mce: Panic when a core has reached
> > a timeout") made it more visible by changing the default behavior of the
> > synchronization timeout from "ignore" to "panic".
> >
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
>
> ...
>
> > +static void machine_check_under_kdump(struct pt_regs *regs, long error_code)
> > +{
> > + struct mce m = {};
> > + char *msg = NULL;
> > + char *nmsg = NULL;
> > + int i;
> > + int worst = 0;
> > + int severity;
> > + int ret;
>
> if you do here
>
> if (mce_cfg.disabled)
> return;
>
> you can use the simple rdmsrl variants and not the _safe() ones with
> exception handling.
I'm not sure why that works, could you elabroate it?
I feel that we need some comment about why it's OK to use rdmsrl_safe()
variant *only* in mce_rdmsrl() (other MCE registers is accessed via rdmsrl(),)
which seems not clear to me from reading current code and git history.
Thanks,
Naoya Horiguchi
next prev parent reply other threads:[~2015-03-06 9:12 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-03 9:01 [PATCH v3 1/2] x86: mce: kexec: switch MCE handler for kexec/kdump Naoya Horiguchi
2015-03-03 9:01 ` [PATCH v3 2/2] x86: mce: comment about MCE synchronization timeout on definition of tolerant Naoya Horiguchi
2015-03-03 18:09 ` [PATCH v3 1/2] x86: mce: kexec: switch MCE handler for kexec/kdump Luck, Tony
2015-03-04 7:41 ` [PATCH v4] " Naoya Horiguchi
2015-03-04 23:12 ` Luck, Tony
2015-03-05 1:24 ` Naoya Horiguchi
2015-03-05 6:45 ` [PATCH v5] " Naoya Horiguchi
2015-03-05 8:57 ` Borislav Petkov
2015-03-05 9:37 ` Naoya Horiguchi
2015-03-06 2:59 ` [PATCH v6] " Naoya Horiguchi
2015-03-06 8:34 ` Borislav Petkov
2015-03-06 9:09 ` Naoya Horiguchi [this message]
2015-03-06 9:27 ` Borislav Petkov
2015-03-06 9:32 ` Naoya Horiguchi
2015-03-06 10:22 ` [PATCH v7] " Naoya Horiguchi
2015-04-06 7:18 ` Naoya Horiguchi
2015-04-06 11:59 ` Borislav Petkov
2015-04-07 8:00 ` Naoya Horiguchi
2015-04-07 8:02 ` [PATCH v8] " Naoya Horiguchi
2015-04-09 6:13 ` Borislav Petkov
2015-04-09 6:57 ` Naoya Horiguchi
2015-04-09 7:02 ` Borislav Petkov
2015-04-09 18:07 ` Luck, Tony
2015-04-09 8:00 ` Ingo Molnar
2015-04-09 8:21 ` Borislav Petkov
2015-04-09 8:59 ` Naoya Horiguchi
2015-04-09 9:53 ` Borislav Petkov
2015-04-09 18:22 ` Luck, Tony
2015-04-09 19:05 ` Borislav Petkov
2015-04-10 0:49 ` Naoya Horiguchi
2015-04-10 4:07 ` Naoya Horiguchi
2015-04-10 7:24 ` Borislav Petkov
2015-04-28 8:41 ` Baoquan He
2015-04-09 8:39 ` Naoya Horiguchi
2015-04-09 9:13 ` Ingo Molnar
2015-04-06 11:56 ` [PATCH v7] " Borislav Petkov
2015-04-07 7:59 ` Naoya Horiguchi
2015-03-06 8:28 ` [PATCH v5] " Borislav Petkov
2015-03-06 5:44 ` [PATCH v4] " Naoya Horiguchi
2015-03-05 8:48 ` Borislav Petkov
2015-03-03 18:53 ` [PATCH v3 1/2] " Borislav Petkov
2015-03-04 7:51 ` Naoya Horiguchi
2015-03-04 9:12 ` Borislav Petkov
2015-03-05 1:27 ` Naoya Horiguchi
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20150306090930.GA14982@hori1.linux.bs1.fc.nec.co.jp \
--to=n-horiguchi@ah.jp.nec.com \
--cc=bp@alien8.de \
--cc=j-nomura@ce.jp.nec.com \
--cc=k-ueda@ct.jp.nec.com \
--cc=linux-kernel@vger.kernel.org \
--cc=prarit@redhat.com \
--cc=tony.luck@intel.com \
--cc=vgoyal@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).