On 07/08/24 at 01:25pm, Sourabh Jain wrote: > Hello Baoquan, > > On 08/07/24 07:09, Baoquan He wrote: > > Hi Sourabh, > > > > On 07/07/24 at 08:54pm, Sourabh Jain wrote: > > > Kernel commit 79365026f869 (crash: add a new kexec flag for hotplug > > > support) has introduced a new kexec flag to generalize hotplug support. > > > The newly introduced kexec flags for hotplug allow architectures to > > > exclude all the required kexec segments from SHA calculation so that > > > the kernel can update them on hotplug events. This was not possible > > > earlier with the KEXEC_UPDATE_ELFCOREHDR kexec flags since it was added > > > only for the elfcorehdr segment. > > > > > > To enable architectures to control the list of kexec segments to exclude > > > when hotplug support is enabled, add a new architecture-specific > > > function named arch_do_exclude_segment. During the SHA calculation, this > > > function gets called to let the architecture decide whether a specific > > > kexec segment should be considered for SHA calculation or not. > > > > > > Note: To avoid breaking backward compatibility, the new kexec flag > > > KEXEC_CRASH_HOTPLUG_SUPPORT is not used for x86 for now. > > For x86, both KEXEC_UPDATE_ELFCOREHDR and KEXEC_CRASH_HOTPLUG_SUPPORT > > should be OK for kexec_file_load. > > Do we even need these flags for kexec_file_load at all? > My understanding is that these flags are only needed for the kexec_load > system call. Oh, sorry, my bad, I must have mixed this with KEXEC_FILE_DEBUG I earlier added when I checked this patchset. I think everything is like what you said. > > > > Your change will make a difference > > between kexec_load and kexec_file_load. > > I am confused by the above statement. > > Given that we don't even send any of the above flags for kexec_file_load, I > am not > sure how these changes make a difference between the two system calls. > > > But I agree with you on the > > backward cmpatibility with KEXEC_CRASH_HOTPLUG_SUPPORT flag. > > > > Anyway, if it's in a hurry to catch up with Simon's new release, this is > > fine, we can change it later. > > It would be great if we could consider this patch series for the next > release, but not at > the cost of breaking any backward compatibility for x86. If you think these > changes are > breaking anything for any kernel version, I would prefer to update my patch > series. > > > Otherwise, we may be better to remove the > > difference, namely, not making x86 only be able to accept > > KEXEC_UPDATE_ELFCOREHDR flag on kexec_load. My personal opinion > > On x86, passing the KEXEC_CRASH_HOTPLUG_SUPPORT kexec bit to kernel versions > 6.5 to 6.9 > with the kexec_load system call will fail with -EINVAL. However, from kernel > 6.10 onward, > both KEXEC_UPDATE_ELFCOREHDR and KEXEC_CRASH_HOTPLUG_SUPPORT kexec bits are > acceptable for x86. > > My proposal is to use KEXEC_UPDATE_ELFCOREHDR on x86 for some time (maybe a > couple of kernel releases), > and eventually switch to KEXEC_CRASH_HOTPLUG_SUPPORT for x86 as well. > > This proposal of shifting to the KEXEC_CRASH_HOTPLUG_SUPPORT kexec bit for > x86 is also mentioned in the > comment for the get_hotplug_kexec_flag function. > > Please let me know your opinion. It sounds like a good plan, thanks for the effort. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
