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[209.85.220.65]) by mx.google.com with SMTPS id p14sor11342050ios.125.2019.07.08.01.36.35 for (Google Transport Security); Mon, 08 Jul 2019 01:36:35 -0700 (PDT) Received-SPF: pass (google.com: domain of kernelfans@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=cOMsmIgo; spf=pass (google.com: domain of kernelfans@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=kernelfans@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5KXyzOyddJPSYupMaPtJc3n1+Qs9tx3Gcb2Q7zVo0M8=; b=cOMsmIgo9no2UIxYQtl0IEhs9cOfaY/6hH+TSNYWkEVjYrtyDyiSG+Pawi7rst84iL aYMFDkhVgQ713ZWq/WNdEtQUY3srXzZzw6MniZc45HgtCzqilWOYA4acWuiVnXpt6yCn dYF7IAD/K7goEhoSST/5CMrxkxRbHqybP9YsubSqGJ+1GueL5Ta2hGjNUlxXwFCc1BEO WZ1+QrX+fsuoq8p3EohEENriAsyZrotv0Lh+a/HQbO5y1KeHvr9lhZOUp8qSZZ5AaeL4 HN3Qosc6+tKtmoIL0erNdz9FKdlU/HmzbGtDN9Tbcxr+J5fBiL5lJMyfjeWH2F/YDbOz ajKA== X-Google-Smtp-Source: APXvYqxjK31i5rr/fwm4g6B2ljMVmD03cvBH/BrY4xuXXtnM1WvV466gG06eq12moEwOXDBhPpeTUgO7m3jJQdXjkBs= X-Received: by 2002:a6b:6f06:: with SMTP id k6mr13682792ioc.32.1562574994974; Mon, 08 Jul 2019 01:36:34 -0700 (PDT) MIME-Version: 1.0 References: <1562300143-11671-1-git-send-email-kernelfans@gmail.com> <1562300143-11671-2-git-send-email-kernelfans@gmail.com> In-Reply-To: From: Pingfan Liu Date: Mon, 8 Jul 2019 16:36:23 +0800 Message-ID: Subject: Re: [PATCH 2/2] x86/numa: instance all parsed numa node To: Thomas Gleixner Cc: x86@kernel.org, Michal Hocko , Dave Hansen , Mike Rapoport , Tony Luck , Andy Lutomirski , Peter Zijlstra , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Andrew Morton , Vlastimil Babka , Oscar Salvador , Pavel Tatashin , Mel Gorman , Benjamin Herrenschmidt , Michael Ellerman , Stephen Rothwell , Qian Cai , Barret Rhoden , Bjorn Helgaas , David Rientjes , linux-mm@kvack.org, LKML Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jul 8, 2019 at 3:44 AM Thomas Gleixner wrote: > > On Fri, 5 Jul 2019, Pingfan Liu wrote: > > > I hit a bug on an AMD machine, with kexec -l nr_cpus=4 option. nr_cpus option > > is used to speed up kdump process, so it is not a rare case. > > But fundamentally wrong, really. > > The rest of the CPUs are in a half baken state and any broadcast event, > e.g. MCE or a stray IPI, will result in a undiagnosable crash. Very appreciate if you can pay more word on it? I tried to figure out your point, but fail. For "a half baked state", I think you concern about LAPIC state, and I expand this point like the following: For IPI: when capture kernel BSP is up, the rest cpus are still loop inside crash_nmi_callback(), so there is no way to eject new IPI from these cpu. Also we disable_local_APIC(), which effectively prevent the LAPIC from responding to IPI, except NMI/INIT/SIPI, which will not occur in crash case. For MCE, I am not sure whether it can broadcast or not between cpus, but as my understanding, it can not. Then is it a problem? >From another view point, is there any difference between nr_cpus=1 and nr_cpus> 1 in crashing case? If stray IPI raises issue to nr_cpus>1, it does for nr_cpus=1. Thanks, Pingfan