From: Eric DeVolder <eric.devolder@oracle.com> To: Baoquan He <bhe@redhat.com> Cc: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [RFC v1 0/8] RFC v1: Kernel handling of CPU and memory hot un/plug for crash Date: Mon, 29 Nov 2021 13:42:13 -0600 [thread overview] Message-ID: <200f923a-d196-7475-99e3-63ff3e73b28e@oracle.com> (raw) In-Reply-To: <20211124090227.GA8026@MiWiFi-R3L-srv> Hi, see below. eric On 11/24/21 03:02, Baoquan He wrote: > Hi, > > On 11/18/21 at 12:49pm, Eric DeVolder wrote: > ...... >> This patchset introduces a generic crash hot un/plug handler that >> registers with the CPU and memory notifiers. Upon CPU or memory >> changes, this generic handler is invoked and performs important >> housekeeping, for example obtaining the appropriate lock, and then >> invokes an architecture specific handler to do the appropriate >> updates. >> >> In the case of x86_64, the arch specific handler generates a new >> elfcorehdr, which reflects the current CPUs and memory regions, into a >> buffer. Since purgatory also does an integrity check via hash digests >> of the loaded segments, purgatory must also be updated with the new > > When I tried to address this with a draft patch, I started with a > different way in which udev rule triggers reloading and only elfcorehdr > segment is updated. The update should be less time consuming. Seems > internal notifier is better in your way. But I didn't update purgatory > since I just skipped the elfcorehdr part when calculate the digest of > segments. The reason from my mind is kernel text, initrd must contribute > most part of the digest, elfcorehdr is much less, and it will simplify > code change more. Doing so let us have no need to touch purgatory at > all. What do you think? Well certainly if purgatory did not need to be updated, then that simplifies matters quite a bit! I do not have any context on the history of including elfcorehdr in the purgatory integrity check. I do agree with you that checking kernel, initrd, boot_params is most important. Perhaps allowing the elfcorehdr data structure to change isn't too bad without including in the integrity check is ok as there is some sanity checking of it by the capture kernel as it reads it for /proc/vmcore setup. > > Still reviewing. Thank you! > >> digests. The arch handler also generates a new purgatory into a >> buffer, performs the hash digests of the new memory segments, and then >> patches purgatory with the new digests. If all succeeds, then the >> elfcorehdr and purgatory buffers over write the existing buffers and >> the new kdump image is live and ready to go. No involvement with >> userspace at all. >
WARNING: multiple messages have this Message-ID (diff)
From: Eric DeVolder <eric.devolder@oracle.com> To: Baoquan He <bhe@redhat.com> Cc: linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com Subject: Re: [RFC v1 0/8] RFC v1: Kernel handling of CPU and memory hot un/plug for crash Date: Mon, 29 Nov 2021 13:42:13 -0600 [thread overview] Message-ID: <200f923a-d196-7475-99e3-63ff3e73b28e@oracle.com> (raw) In-Reply-To: <20211124090227.GA8026@MiWiFi-R3L-srv> Hi, see below. eric On 11/24/21 03:02, Baoquan He wrote: > Hi, > > On 11/18/21 at 12:49pm, Eric DeVolder wrote: > ...... >> This patchset introduces a generic crash hot un/plug handler that >> registers with the CPU and memory notifiers. Upon CPU or memory >> changes, this generic handler is invoked and performs important >> housekeeping, for example obtaining the appropriate lock, and then >> invokes an architecture specific handler to do the appropriate >> updates. >> >> In the case of x86_64, the arch specific handler generates a new >> elfcorehdr, which reflects the current CPUs and memory regions, into a >> buffer. Since purgatory also does an integrity check via hash digests >> of the loaded segments, purgatory must also be updated with the new > > When I tried to address this with a draft patch, I started with a > different way in which udev rule triggers reloading and only elfcorehdr > segment is updated. The update should be less time consuming. Seems > internal notifier is better in your way. But I didn't update purgatory > since I just skipped the elfcorehdr part when calculate the digest of > segments. The reason from my mind is kernel text, initrd must contribute > most part of the digest, elfcorehdr is much less, and it will simplify > code change more. Doing so let us have no need to touch purgatory at > all. What do you think? Well certainly if purgatory did not need to be updated, then that simplifies matters quite a bit! I do not have any context on the history of including elfcorehdr in the purgatory integrity check. I do agree with you that checking kernel, initrd, boot_params is most important. Perhaps allowing the elfcorehdr data structure to change isn't too bad without including in the integrity check is ok as there is some sanity checking of it by the capture kernel as it reads it for /proc/vmcore setup. > > Still reviewing. Thank you! > >> digests. The arch handler also generates a new purgatory into a >> buffer, performs the hash digests of the new memory segments, and then >> patches purgatory with the new digests. If all succeeds, then the >> elfcorehdr and purgatory buffers over write the existing buffers and >> the new kdump image is live and ready to go. No involvement with >> userspace at all. > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
next prev parent reply other threads:[~2021-11-29 19:45 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-11-18 17:49 [RFC v1 0/8] RFC v1: Kernel handling of CPU and memory hot un/plug for crash Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 1/8] crash: fix minor typo/bug in debug message Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-24 1:17 ` Baoquan He 2021-11-24 1:17 ` Baoquan He 2021-11-18 17:49 ` [RFC v1 2/8] crash hp: Introduce CRASH_HOTPLUG configuration options Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 3/8] crash hp: definitions and prototypes for crash hotplug support Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 4/8] crash hp: generic crash hotplug support infrastructure Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 5/8] crash hp: kexec_file changes for use by crash hotplug handler Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 6/8] crash hp: Add x86 crash hotplug state items to kimage Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 7/8] crash hp: Add x86 crash hotplug support for kexec_file_load Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-18 17:49 ` [RFC v1 8/8] crash hp: Add x86 crash hotplug support for bzImage Eric DeVolder 2021-11-18 17:49 ` Eric DeVolder 2021-11-19 2:37 ` [RFC v1 0/8] RFC v1: Kernel handling of CPU and memory hot un/plug for crash Baoquan He 2021-11-19 2:37 ` Baoquan He 2021-11-24 9:02 ` Baoquan He 2021-11-24 9:02 ` Baoquan He 2021-11-29 19:42 ` Eric DeVolder [this message] 2021-11-29 19:42 ` Eric DeVolder 2021-12-01 12:59 ` Baoquan He 2021-12-01 12:59 ` Baoquan He 2021-12-07 20:04 ` Eric DeVolder 2021-12-07 20:04 ` Eric DeVolder 2021-11-29 8:45 ` Sourabh Jain 2021-11-29 8:45 ` Sourabh Jain 2021-11-29 20:00 ` Eric DeVolder 2021-11-29 20:00 ` Eric DeVolder
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=200f923a-d196-7475-99e3-63ff3e73b28e@oracle.com \ --to=eric.devolder@oracle.com \ --cc=bhe@redhat.com \ --cc=boris.ostrovsky@oracle.com \ --cc=bp@alien8.de \ --cc=dave.hansen@linux.intel.com \ --cc=dyoung@redhat.com \ --cc=ebiederm@xmission.com \ --cc=efault@gmx.de \ --cc=hpa@zytor.com \ --cc=kexec@lists.infradead.org \ --cc=konrad.wilk@oracle.com \ --cc=linux-kernel@vger.kernel.org \ --cc=mingo@redhat.com \ --cc=nramas@linux.microsoft.com \ --cc=robh@kernel.org \ --cc=rppt@kernel.org \ --cc=tglx@linutronix.de \ --cc=thomas.lendacky@amd.com \ --cc=vgoyal@redhat.com \ --cc=x86@kernel.org \ /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: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is an external index of several public inboxes, see mirroring instructions on how to clone and mirror all data and code used by this external index.