Messages in this thread | | | Date | Thu, 17 Mar 2022 16:16:07 +0530 | Subject | Re: [PATCH v5 4/8] crash: generic crash hotplug support infrastructure | From | Sourabh Jain <> |
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On 15/03/22 19:42, Eric DeVolder wrote: > > > On 3/15/22 07:08, Sourabh Jain wrote: >> Hello Eric, >> >> On 03/03/22 21:57, Eric DeVolder wrote: >>> This patch introduces a generic crash hot plug/unplug infrastructure >>> for CPU and memory changes. Upon CPU and memory changes, a generic >>> crash_hotplug_handler() obtains the appropriate lock, does some >>> important house keeping and then dispatches the hot plug/unplug event >>> to the architecture specific arch_crash_hotplug_handler(), and when >>> that handler returns, the lock is released. >>> >>> This patch modifies crash_core.c to implement a subsys_initcall() >>> function that installs handlers for hot plug/unplug events. If CPU >>> hotplug is enabled, then cpuhp_setup_state() is invoked to register a >>> handler for CPU changes. Similarly, if memory hotplug is enabled, then >>> register_memory_notifier() is invoked to install a handler for memory >>> changes. These handlers in turn invoke the common generic handler >>> crash_hotplug_handler(). >>> >>> On the CPU side, cpuhp_setup_state_nocalls() is invoked with parameter >>> CPUHP_AP_ONLINE_DYN. While this works, when a CPU is being unplugged, >>> the CPU still shows up in foreach_present_cpu() during the regeneration >>> of the new CPU list, thus the need to explicitly check and exclude the >>> soon-to-be offlined CPU in crash_prepare_elf64_headers(). >>> >>> On the memory side, each un/plugged memory block passes through the >>> handler. For example, if a 1GiB DIMM is hotplugged, that generate 8 >>> memory events, one for each 128MiB memblock. >>> >>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> >>> --- >>> include/linux/kexec.h | 16 +++++++ >>> kernel/crash_core.c | 108 >>> ++++++++++++++++++++++++++++++++++++++++++ >>> 2 files changed, 124 insertions(+) >>> >>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >>> index d7b59248441b..b11d75a6b2bc 100644 >>> --- a/include/linux/kexec.h >>> +++ b/include/linux/kexec.h >>> @@ -300,6 +300,13 @@ struct kimage { >>> /* Information for loading purgatory */ >>> struct purgatory_info purgatory_info; >>> + >>> +#ifdef CONFIG_CRASH_HOTPLUG >>> + bool hotplug_event; >>> + int offlinecpu; >>> + bool elf_index_valid; >>> + int elf_index; >> >> How about keeping an array to track all kexec segment index need to >> be updated in >> crash hotplug handler. >> >> struct hp_segment { >> name; >> index; >> is_valid; >> } >> >> It will be helpful if architecture need to updated multiple kexec >> segments for a hotplug event. >> >> For example, on PowerPC, we might need to update FDT and elfcorehdr >> on memory hot plug/unplug. >> >> Thanks, >> Sourabh Jain > > Sourabh, > I'm OK with that. Another idea might be if there are just two, and one > of them is elfcorehdr, then perhaps in addition to elf_index and > elf_index_valid, maybe we add an arch_index and arch_index_valid? In > the case of PPC, the FDT would be stored in arch_index?
Yes it seems like we might not need to keep more than two kexec indexes. Since this indexes are arch specific lets push them to struct kimage_arch (part of kimage). So for now I will push fdt_index to struct kimage_arch.
Thanks, Sourabh Jain
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