From: Borislav Petkov <bp@alien8.de>
To: Pingfan Liu <kernelfans@gmail.com>
Cc: Gleixner <tglx@linutronix.de>, Andy Lutomirski <luto@kernel.org>,
x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
"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, Dave Young <dyoung@redhat.com>,
Baoquan He <bhe@redhat.com>,
kexec@lists.infradead.org
Subject: Re: [PATCHv2 0/4] x86/mce: protect nr_cpus from rebooting by broadcast mce
Date: Fri, 30 Aug 2019 16:11:56 +0200 [thread overview]
Message-ID: <20190830141156.GB30413@zn.tnic> (raw)
In-Reply-To: <1566874943-4449-1-git-send-email-kernelfans@gmail.com>
On Tue, Aug 27, 2019 at 11:02:19AM +0800, Pingfan Liu wrote:
> v1 -> v2: fix compile warning and error on x86_32
>
>
> 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.
>
> *** 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.
One thing is not clear to me: are you "fixing" a hypothetical case here
or have you *actually* experienced an MCE happening while kdumping with
nr_cpus < num_online_cpus()?
Btw, pls do not use lkml.org to refer to previous mails but
http://lkml.kernel.org/r/<Message-ID>
Thx.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2019-08-30 14:12 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-27 3:02 [PATCHv2 0/4] x86/mce: protect nr_cpus from rebooting by broadcast mce Pingfan Liu
2019-08-27 3:02 ` [PATCHv2 1/4] x86/apic: correct the ENO in generic_processor_info() Pingfan Liu
2019-08-27 3:02 ` [PATCHv2 2/4] x86/apic: record capped cpu " Pingfan Liu
2019-08-27 3:02 ` [PATCHv2 3/4] x86/smp: send capped cpus to a stable state when smp_init() Pingfan Liu
2019-08-27 3:02 ` [PATCHv2 4/4] x86/smp: disallow MCE handler on rebooting AP Pingfan Liu
2019-08-30 14:11 ` Borislav Petkov [this message]
2019-09-02 4:26 ` [PATCHv2 0/4] x86/mce: protect nr_cpus from rebooting by broadcast mce Pingfan Liu
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