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cpu hotplug events are independent of memory >> hotplug events, but both are written into the elfcorehdr, so in reality >> yes... The elfcorehdr contains a single list of Phdrs describing CPUs and >> crash memory ranges; the entire list is re-written on a hotplug change. > > Then technically also yes. Otherwise your crash information will contain > wrong CPU numbers. > > How has that not been a problem until now...? > > I.e., offline a bunch of CPUs and then cause a crash dump. > > Hmm. > There is a solution for updating the elfcorehdr today, for when say a bunch of CPUs are offlined. It is done via userspace udev rules to do a unload-then-reload of the entire crash kernel system (kernel, initrd, purgatory, boot_params, and of course elfcorehdr). This performs extremely poorly in highly dynamic hotplug situations (such as when adding alot of memory to a vm), and thus the attempt at this solution. But I sense I missing your point? 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charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 11/2/22 13:49, Borislav Petkov wrote: > On Wed, Nov 02, 2022 at 11:54:08AM -0500, Eric DeVolder wrote: >> Technically the answer is no; cpu hotplug events are independent of memory >> hotplug events, but both are written into the elfcorehdr, so in reality >> yes... The elfcorehdr contains a single list of Phdrs describing CPUs and >> crash memory ranges; the entire list is re-written on a hotplug change. > > Then technically also yes. Otherwise your crash information will contain > wrong CPU numbers. > > How has that not been a problem until now...? > > I.e., offline a bunch of CPUs and then cause a crash dump. > > Hmm. > There is a solution for updating the elfcorehdr today, for when say a bunch of CPUs are offlined. It is done via userspace udev rules to do a unload-then-reload of the entire crash kernel system (kernel, initrd, purgatory, boot_params, and of course elfcorehdr). This performs extremely poorly in highly dynamic hotplug situations (such as when adding alot of memory to a vm), and thus the attempt at this solution. But I sense I missing your point? Thanks! eric _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec