From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1cqcdD-000284-0h for kexec@lists.infradead.org; Wed, 22 Mar 2017 09:32:43 +0000 Subject: Re: [PATCH v3 1/3] kexec: Move vmcoreinfo out of the kernel's .bss section References: <1489989033-1179-1-git-send-email-xlpang@redhat.com> <87pohbz4lo.fsf@xmission.com> <20170322025536.GA4424@dhcp-128-65.nay.redhat.com> <87pohaxam1.fsf@xmission.com> <20170322043004.GB4424@dhcp-128-65.nay.redhat.com> From: Xunlei Pang Message-ID: <58D24543.5020700@redhat.com> Date: Wed, 22 Mar 2017 17:34:59 +0800 MIME-Version: 1.0 In-Reply-To: <20170322043004.GB4424@dhcp-128-65.nay.redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: xlpang@redhat.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Dave Young , "Eric W. Biederman" Cc: Baoquan He , Xunlei Pang , Atsushi Kumagai , Petr Tesarik , linux-kernel@vger.kernel.org, hbathini@linux.vnet.ibm.com, akpm@linux-foundation.org, holzheu@linux.vnet.ibm.com, kexec@lists.infradead.org On 03/22/2017 at 12:30 PM, Dave Young wrote: > On 03/21/17 at 10:18pm, Eric W. Biederman wrote: >> Dave Young writes: >> >>> On 03/20/17 at 10:33pm, Eric W. Biederman wrote: >>>> Xunlei Pang writes: >>>> >>>>> As Eric said, >>>>> "what we need to do is move the variable vmcoreinfo_note out >>>>> of the kernel's .bss section. And modify the code to regenerate >>>>> and keep this information in something like the control page. >>>>> >>>>> Definitely something like this needs a page all to itself, and ideally >>>>> far away from any other kernel data structures. I clearly was not >>>>> watching closely the data someone decided to keep this silly thing >>>>> in the kernel's .bss section." >>>>> >>>>> This patch allocates extra pages for these vmcoreinfo_XXX variables, >>>>> one advantage is that it enhances some safety of vmcoreinfo, because >>>>> vmcoreinfo now is kept far away from other kernel data structures. >>>> Can you preceed this patch with a patch that removes CRASHTIME from >>>> vmcoreinfo? If someone actually cares we can add a separate note that holds >>>> a 64bit crashtime in the per cpu notes. >>> I think makedumpfile is using it, but I also vote to remove the >>> CRASHTIME. It is better not to do this while crashing and a makedumpfile >>> userspace patch is needed to drop the use of it. >>> By moving the CRASHTIME info to the cpu note of crashed cpu may be a good way. In kdump kernel, notes of vmcore elfhdr will be merged into one big note section, I don't know how makedumpfile or crash handle the big note section? If they process the note in some order, breakage will definitely happen... There is also a fadump may be affected. Regards, Xunlei >>>> As we are looking at reliability concerns removing CRASHTIME should make >>>> everything in vmcoreinfo a boot time constant. Which should simplify >>>> everything considerably. >>> It is a nice improvement.. >> We also need to take a close look at what s390 is doing with vmcoreinfo. >> As apparently it is reading it in a different kind of crashdump process. > Yes, need careful review from s390 and maybe ppc64 especially about > patch 2/3, better to have comments from IBM about s390 dump tool and ppc > fadump. Added more cc. > > Thanks > Dave > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec