Hi Eric, On 02/09/22 at 02:56pm, Eric DeVolder wrote: > When the kdump service is loaded, if a CPU or memory is hot > un/plugged, the crash elfcorehdr (for x86), which describes the CPUs > and memory in the system, must also be updated, else the resulting > vmcore is inaccurate (eg. missing either CPU context or memory > regions). This version looks much better. I am gonna to review this week and give it a shot on a machine. Can you share your test steps? I have knowledge about mem hotplug, but haven't tried cpu hotplug yet. Thanks Baoquan > > The current solution utilizes udev to initiate an unload-then-reload > of the kdump image (e. kernel, initrd, boot_params, puratory and > elfcorehdr) by the userspace kexec utility. In previous posts I have > outlined the significant performance problems related to offloading > this activity to userspace. > > 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, and overwrites the old one in memory. No involvement > with userspace needed. > > To realize the benefits/test this patchset, one must make a couple > of minor changes to userspace: > > - Disable the udev rule for updating kdump on hot un/plug changes > Eg. on RHEL: rm -f /usr/lib/udev/rules.d/98-kexec.rules > or other technique to neuter the rule. > > - Change to the kexec_file_load for loading the kdump kernel: > Eg. on RHEL: in /usr/bin/kdumpctl, change to: > standard_kexec_args="-p -d -s" > which adds the -s to select kexec_file_load syscall. > > This patchset supports kexec_load with a modified kexec userspace > utility, and a working changeset to the kexec userspace utility > is provided here (and to use, the above change to standard_kexec_args > would be, for example, to append --hotplug-size=262144 instead of -s). > > diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c > index 9826f6d..06adb7e 100644 > --- a/kexec/arch/i386/crashdump-x86.c > +++ b/kexec/arch/i386/crashdump-x86.c > @@ -48,6 +48,7 @@ > #include <x86/x86-linux.h> > > extern struct arch_options_t arch_options; > +extern unsigned long long hotplug_size; > > static int get_kernel_page_offset(struct kexec_info *UNUSED(info), > struct crash_elf_info *elf_info) > @@ -975,6 +976,13 @@ int load_crashdump_segments(struct kexec_info *info, char* mod_cmdline, > } else { > memsz = bufsz; > } > + > + /* If hotplug support enabled, use that size */ > + if (hotplug_size) { > + memsz = hotplug_size; > + } > + > + info->elfcorehdr = > elfcorehdr = add_buffer(info, tmp, bufsz, memsz, align, min_base, > max_addr, -1); > dbgprintf("Created elf header segment at 0x%lx\n", elfcorehdr); > diff --git a/kexec/kexec.c b/kexec/kexec.c > index f63b36b..9569d9a 100644 > --- a/kexec/kexec.c > +++ b/kexec/kexec.c > @@ -58,6 +58,7 @@ > > unsigned long long mem_min = 0; > unsigned long long mem_max = ULONG_MAX; > +unsigned long long hotplug_size = 0; > static unsigned long kexec_flags = 0; > /* Flags for kexec file (fd) based syscall */ > static unsigned long kexec_file_flags = 0; > @@ -672,6 +673,12 @@ static void update_purgatory(struct kexec_info *info) > if (info->segment[i].mem == (void *)info->rhdr.rel_addr) { > continue; > } > + /* Don't include elfcorehdr in the checksum, if hotplug > + * support enabled. > + */ > + if (hotplug_size && (info->segment[i].mem == (void *)info->elfcorehdr)) { > + continue; > + } > sha256_update(&ctx, info->segment[i].buf, > info->segment[i].bufsz); > nullsz = info->segment[i].memsz - info->segment[i].bufsz; > @@ -1504,6 +1511,17 @@ int main(int argc, char *argv[]) > case OPT_PRINT_CKR_SIZE: > print_crashkernel_region_size(); > return 0; > + case OPT_HOTPLUG_SIZE: > + /* Reserved the specified size for hotplug growth */ > + hotplug_size = strtoul(optarg, &endptr, 0); > + if (*endptr) { > + fprintf(stderr, > + "Bad option value in --hotplug-size=%s\n", > + optarg); > + usage(); > + return 1; > + } > + break; > default: > break; > } > diff --git a/kexec/kexec.h b/kexec/kexec.h > index 595dd68..b30dda4 100644 > --- a/kexec/kexec.h > +++ b/kexec/kexec.h > @@ -169,6 +169,7 @@ struct kexec_info { > int command_line_len; > > int skip_checks; > + unsigned long elfcorehdr; > }; > > struct arch_map_entry { > @@ -231,7 +232,8 @@ extern int file_types; > #define OPT_PRINT_CKR_SIZE 262 > #define OPT_LOAD_LIVE_UPDATE 263 > #define OPT_EXEC_LIVE_UPDATE 264 > -#define OPT_MAX 265 > +#define OPT_HOTPLUG_SIZE 265 > +#define OPT_MAX 266 > #define KEXEC_OPTIONS \ > { "help", 0, 0, OPT_HELP }, \ > { "version", 0, 0, OPT_VERSION }, \ > @@ -258,6 +260,7 @@ extern int file_types; > { "debug", 0, 0, OPT_DEBUG }, \ > { "status", 0, 0, OPT_STATUS }, \ > { "print-ckr-size", 0, 0, OPT_PRINT_CKR_SIZE }, \ > + { "hotplug-size", 2, 0, OPT_HOTPLUG_SIZE }, \ > > #define KEXEC_OPT_STR "h?vdfixyluet:pscaS" > > > Regards, > eric > --- > v4: 9feb2022 > - Refactored patches per Baoquan suggestsions. > - A few corrections, per Baoquan. > > v3: 10jan2022 > https://lkml.org/lkml/2022/1/10/1212 > - Rebasing per Baoquan He request. > - Changed memory notifier per David Hildenbrand. > - Providing example kexec userspace change in cover letter. > > RFC v2: 7dec2021 > https://lkml.org/lkml/2021/12/7/1088 > - Acting upon Baoquan He suggestion of removing elfcorehdr from > the purgatory list of segments, removed purgatory code from > patchset, and it is signficiantly simpler now. > > RFC v1: 18nov2021 > https://lkml.org/lkml/2021/11/18/845 > - working patchset demonstrating kernel handling of hotplug > updates to x86 elfcorehdr for kexec_file_load > > RFC: 14dec2020 > https://lkml.org/lkml/2020/12/14/532 > - proposed concept of allowing kernel to handle hotplug update > of elfcorehdr > --- > > Eric DeVolder (10): > crash: fix minor typo/bug in debug message > crash hp: Introduce CRASH_HOTPLUG configuration options > crash hp: definitions and prototype changes > crash hp: prototype change for crash_prepare_elf64_headers > crash hp: introduce helper functions un/map_crash_pages > crash hp: generic crash hotplug support infrastructure > crash hp: exclude elfcorehdr from the segment digest > crash hp: exclude hot remove cpu from elfcorehdr notes > crash hp: Add x86 crash hotplug support for kexec_file_load > crash hp: Add x86 crash hotplug support for kexec_load > > arch/arm64/kernel/machine_kexec_file.c | 6 +- > arch/powerpc/kexec/file_load_64.c | 2 +- > arch/x86/Kconfig | 26 +++++ > arch/x86/kernel/crash.c | 123 ++++++++++++++++++++- > include/linux/kexec.h | 23 +++- > kernel/crash_core.c | 146 +++++++++++++++++++++++++ > kernel/kexec_file.c | 15 ++- > 7 files changed, 331 insertions(+), 10 deletions(-) > > -- > 2.27.0 > _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec