From: Pingfan Liu <kernelfans@gmail.com>
To: Dave Young <dyoung@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Andy Lutomirski <luto@kernel.org>,
x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Masami Hiramatsu <mhiramat@kernel.org>, Qian Cai <cai@lca.pw>,
Vlastimil Babka <vbabka@suse.cz>,
Daniel Drake <drake@endlessm.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Michal Hocko <mhocko@suse.com>,
Eric Biederman <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org, Baoquan He <bhe@redhat.com>,
kexec@lists.infradead.org, tony.luck@intel.com,
Xunlei Pang <xlpang@linux.alibaba.com>
Subject: Re: [PATCH 0/4] x86/mce: protect nr_cpus from rebooting by broadcast mce
Date: Wed, 7 Aug 2019 15:52:26 +0800 [thread overview]
Message-ID: <20190807075226.GA10392@mypc> (raw)
In-Reply-To: <20190807025843.GA4776@dhcp-128-65.nay.redhat.com>
On Wed, Aug 07, 2019 at 11:00:41AM +0800, Dave Young wrote:
> Add Tony and Xunlei in cc.
> On 08/05/19 at 04:58pm, Pingfan Liu wrote:
> > This series include two related groups:
> > [1-3/4]: protect nr_cpus from rebooting by broadcast mce
> > [4/4]: improve "kexec -l" robustness against broadcast mce
> >
> > When I tried to fix [1], Thomas raised concern about the nr_cpus' vulnerability
> > to unexpected rebooting by broadcast mce. After analysis, I think only the
> > following first case suffers from the rebooting by broadcast mce. [1-3/4] aims
> > to fix that issue.
>
> I did not understand and read the MCE details, but we previously had a
> MCE problem, Xunlei fixed in below commit:
> commit 5bc329503e8191c91c4c40836f062ef771d8ba83
> Author: Xunlei Pang <xlpang@redhat.com>
> Date: Mon Mar 13 10:50:19 2017 +0100
>
> x86/mce: Handle broadcasted MCE gracefully with kexec
>
> I wonder if this is same issue or not. Also the old discussion is in
> below thread:
> https://lore.kernel.org/patchwork/patch/753530/
>
> Tony raised similar questions, but I'm not sure if it is still a problem
> or it has been fixed.
>
Xunlei's patch is the precondition of the stability for the case 2: boot up by "kexec -p nr_cpus="
For case1/3, extra effort is needed.
Thanks,
Pingfan
> >
> > *** Back ground ***
> >
> > On x86 it's required to have all logical CPUs set CR4.MCE=1. Otherwise, a
> > broadcast MCE observing CR4.MCE=0b on any core will shutdown the machine.
> >
> > The option 'nosmt' has already complied with the above rule by Thomas's patch.
> > For detail, refer to 506a66f3748 (Revert "x86/apic: Ignore secondary threads if
> > nosmt=force")
> >
> > But for nr_cpus option, the exposure to broadcast MCE is a little complicated,
> > and can be categorized into three cases.
> >
> > -1. boot up by BIOS. Since no one set CR4.MCE=1, nr_cpus risks rebooting by
> > broadcast MCE.
> >
> > -2. boot up by "kexec -p nr_cpus=". Since the 1st kernel has all cpus'
> > CR4.MCE=1 set before kexec -p, nr_cpus is free of rebooting by broadcast MCE.
> > Furthermore, the crashed kernel's wreckage, including page table and text, is
> > not touched by capture kernel. Hence if MCE event happens on capped cpu,
> > do_machine_check->__mc_check_crashing_cpu() runs smoothly and returns
> > immediately, the capped cpu is still pinned on "halt".
> >
> > -3. boot up by "kexec -l nr_cpus=". As "kexec -p", it is free of rebooting by
> > broadcast MCE. But the 1st kernel's wreckage is discarded and changed. when
> > capped cpus execute do_machine_check(), they may crack the new kernel. But
> > this is not related with broadcast MCE, and need an extra fix.
> >
> > *** Solution ***
> > "nr_cpus" can not follow the same way as "nosmt". Because nr_cpus limits the
> > allocation of percpu area and some other kthread memory, which is critical to
> > cpu hotplug framework. Instead, developing a dedicated SIPI callback
> > make_capped_cpu_stable() for capped cpu, which does not lean on percpu area to
> > work.
> >
> > [1]: https://lkml.org/lkml/2019/7/5/3
> >
> > To: Gleixner <tglx@linutronix.de>
> > To: Andy Lutomirski <luto@kernel.org>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > To: x86@kernel.org
> > Cc: Masami Hiramatsu <mhiramat@kernel.org>
> > Cc: Qian Cai <cai@lca.pw>
> > Cc: Vlastimil Babka <vbabka@suse.cz>
> > Cc: Daniel Drake <drake@endlessm.com>
> > Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Cc: Michal Hocko <mhocko@suse.com>
> > Cc: Eric Biederman <ebiederm@xmission.com>
> > Cc: linux-kernel@vger.kernel.org
> > Cc: Dave Young <dyoung@redhat.com>
> > Cc: Baoquan He <bhe@redhat.com>
> > Cc: kexec@lists.infradead.org
> >
> > ---
> > Pingfan Liu (4):
> > x86/apic: correct the ENO in generic_processor_info()
> > x86/apic: record capped cpu in generic_processor_info()
> > x86/smp: send capped cpus to a stable state when smp_init()
> > x86/smp: disallow MCE handler on rebooting AP
> >
> > arch/x86/include/asm/apic.h | 1 +
> > arch/x86/include/asm/smp.h | 3 ++
> > arch/x86/kernel/apic/apic.c | 23 ++++++++----
> > arch/x86/kernel/cpu/common.c | 7 ++++
> > arch/x86/kernel/smp.c | 8 +++++
> > arch/x86/kernel/smpboot.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
> > kernel/smp.c | 6 ++++
> > 7 files changed, 124 insertions(+), 7 deletions(-)
> >
> > --
> > 2.7.5
> >
>
> Thanks
> Dave
next prev parent reply other threads:[~2019-08-07 7:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-05 8:58 [PATCH 0/4] x86/mce: protect nr_cpus from rebooting by broadcast mce Pingfan Liu
2019-08-05 8:58 ` [PATCH 1/4] x86/apic: correct the ENO in generic_processor_info() Pingfan Liu
2019-08-05 8:58 ` [PATCH 2/4] x86/apic: record capped cpu " Pingfan Liu
2019-08-08 0:17 ` kbuild test robot
2019-08-08 0:17 ` [RFC PATCH] x86/apic: __cpu_capped_mask can be static kbuild test robot
2019-08-05 8:58 ` [PATCH 3/4] x86/smp: send capped cpus to a stable state when smp_init() Pingfan Liu
2019-08-08 1:20 ` kbuild test robot
2019-08-08 1:20 ` [RFC PATCH] x86/smp: __cpu_capped_done_mask can be static kbuild test robot
2019-08-08 2:36 ` [PATCH 3/4] x86/smp: send capped cpus to a stable state when smp_init() kbuild test robot
2019-08-08 5:18 ` kbuild test robot
2019-08-05 8:58 ` [PATCH 4/4] x86/smp: disallow MCE handler on rebooting AP Pingfan Liu
2019-08-07 3:00 ` [PATCH 0/4] x86/mce: protect nr_cpus from rebooting by broadcast mce Dave Young
2019-08-07 7:52 ` Pingfan Liu [this message]
2019-08-07 13:07 ` Thomas Gleixner
2019-08-08 5:41 ` Pingfan Liu
2019-08-08 6:51 ` Thomas Gleixner
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=20190807075226.GA10392@mypc \
--to=kernelfans@gmail.com \
--cc=bhe@redhat.com \
--cc=bp@alien8.de \
--cc=cai@lca.pw \
--cc=dave.hansen@linux.intel.com \
--cc=drake@endlessm.com \
--cc=dyoung@redhat.com \
--cc=ebiederm@xmission.com \
--cc=hpa@zytor.com \
--cc=jacob.jun.pan@linux.intel.com \
--cc=kexec@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mhiramat@kernel.org \
--cc=mhocko@suse.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=tony.luck@intel.com \
--cc=vbabka@suse.cz \
--cc=x86@kernel.org \
--cc=xlpang@linux.alibaba.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).