Messages in this thread | | | Date | Fri, 10 Feb 2023 10:51:14 -0600 | Subject | Re: [PATCH v18 3/7] crash: add generic infrastructure for crash hotplug support | From | Eric DeVolder <> |
| |
On 2/9/23 13:10, Sourabh Jain wrote: > Hello Eric, > > On 01/02/23 04:12, Eric DeVolder wrote: >> To support crash hotplug, a mechanism is needed to update the crash >> elfcorehdr upon CPU or memory changes (eg. hot un/plug or off/ >> onlining). >> >> To track CPU changes, callbacks are registered with the cpuhp >> mechanism via cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN). The >> crash hotplug elfcorehdr update has no explicit ordering requirement >> (relative to other cpuhp states), so meets the criteria for >> utilizing CPUHP_BP_PREPARE_DYN. CPUHP_BP_PREPARE_DYN is a dynamic >> state and avoids the need to introduce a new state for crash >> hotplug. Also, this is the last state in the PREPARE group, just >> prior to the STARTING group, which is very close to the CPU >> starting up in an plug/online situation, or stopping in a unplug/ >> offline situation. This minimizes the window of time during an >> actual plug/online or unplug/offline situation in which the >> elfcorehdr would be inaccurate. >> >> Note, that when a CPU is being unplugged/offlined, the CPU is still >> in the foreach_present_cpu() during the regeneration of the >> elfcorehdr. Thus there is a need to explicitly check and exclude >> the soon-to-be offlined CPU. See patch 'kexec: exclude hot remove >> cpu from elfcorehdr notes'. >> >> To track memory changes, a notifier is registered to capture the >> memblock MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier(). >> >> The cpu callbacks and memory notifiers invoke handle_hotplug_event() >> which performs needed tasks and then dispatches the event to the >> architecture specific arch_crash_handle_hotplug_event() to update the >> elfcorehdr with the current state of CPUs and memory. During the >> process, the kexec_lock is held. >> >> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> >> Acked-by: Baoquan He <bhe@redhat.com> >> --- >> include/linux/crash_core.h | 9 +++ >> include/linux/kexec.h | 12 ++++ >> kernel/crash_core.c | 139 +++++++++++++++++++++++++++++++++++++ >> 3 files changed, 160 insertions(+) >> >> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h >> index de62a722431e..ed868d237c07 100644 >> --- a/include/linux/crash_core.h >> +++ b/include/linux/crash_core.h >> @@ -84,4 +84,13 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram, >> int parse_crashkernel_low(char *cmdline, unsigned long long system_ram, >> unsigned long long *crash_size, unsigned long long *crash_base); >> +#define KEXEC_CRASH_HP_NONE 0 >> +#define KEXEC_CRASH_HP_REMOVE_CPU 1 >> +#define KEXEC_CRASH_HP_ADD_CPU 2 >> +#define KEXEC_CRASH_HP_REMOVE_MEMORY 3 >> +#define KEXEC_CRASH_HP_ADD_MEMORY 4 >> +#define KEXEC_CRASH_HP_INVALID_CPU -1U >> + >> +struct kimage; >> + >> #endif /* LINUX_CRASH_CORE_H */ >> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >> index 27ef420c7a45..a52624ae4452 100644 >> --- a/include/linux/kexec.h >> +++ b/include/linux/kexec.h >> @@ -33,6 +33,7 @@ extern note_buf_t __percpu *crash_notes; >> #include <linux/compat.h> >> #include <linux/ioport.h> >> #include <linux/module.h> >> +#include <linux/highmem.h> >> #include <asm/kexec.h> >> /* Verify architecture specific macros are defined */ >> @@ -371,6 +372,13 @@ struct kimage { >> struct purgatory_info purgatory_info; >> #endif >> +#ifdef CONFIG_CRASH_HOTPLUG >> + int hp_action; >> + unsigned int offlinecpu; >> + bool elfcorehdr_index_valid; >> + int elfcorehdr_index; > > May be I am reiterating myself but I think we can manage without elfcorehdr_index_valid. > > Here is how: > Initialize the elfcorehdr_index with a negative value in do_kimage_alloc_init > function (it is called for both kexec_load and kexec_file_load). > > Now when the control reaches to handle_hotplug_event function and if elfcorehdr_index > has negative value find the correct index and re-initialize the elfcorehdr_index. > > Thoughts? > > Thanks, > Sourabh Jain > ok, I'll eliminate elfcorehdr_index_valid. eric
| |