Messages in this thread | | | Date | Tue, 26 Apr 2022 09:36:59 +0530 | Subject | Re: [PATCH v7 4/8] crash: add generic infrastructure for crash hotplug support | From | Sourabh Jain <> |
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On 15/04/22 03:59, Eric DeVolder wrote: > Hi Baoquan, > Inline comments below. > Thanks! > eric > > On 4/13/22 21:45, Baoquan He wrote: >> On 04/13/22 at 12:42pm, Eric DeVolder wrote: >>> Upon CPU and memory changes, a generic crash_hotplug_handler() >>> dispatches the hot plug/unplug event to the architecture specific >>> arch_crash_hotplug_handler(). During the process, the kexec_mutex >>> is held. >>> >>> To support cpu hotplug, a callback is registered to capture the >>> CPUHP_AP_ONLINE_DYN online and ofline events via >>> cpuhp_setup_state_nocalls(). >>> >>> To support memory hotplug, a notifier is registered to capture the >>> MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier(). >>> >>> The cpu callback and memory notifier then call crash_hotplug_handler() >>> to handle the hot plug/unplug event. >>> >>> Signed-off-by: Eric DeVolder <eric.devolder@oracle.com> >>> --- >>> include/linux/kexec.h | 16 +++++++ >>> kernel/crash_core.c | 101 >>> ++++++++++++++++++++++++++++++++++++++++++ >>> 2 files changed, 117 insertions(+) >>> >>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >>> index f93f2591fc1e..02daff1f47dd 100644 >>> --- a/include/linux/kexec.h >>> +++ b/include/linux/kexec.h >>> @@ -306,6 +306,13 @@ struct kimage { >>> /* Information for loading purgatory */ >>> struct purgatory_info purgatory_info; >>> + >>> +#ifdef CONFIG_CRASH_HOTPLUG >>> + bool hotplug_event; >>> + unsigned int offlinecpu; >>> + bool elfcorehdr_index_valid; >>> + int elfcorehdr_index; >>> +#endif >>> #endif >>> #ifdef CONFIG_IMA_KEXEC >>> @@ -322,6 +329,15 @@ struct kimage { >>> unsigned long elf_load_addr; >>> }; >>> +#ifdef CONFIG_CRASH_HOTPLUG >>> +void arch_crash_hotplug_handler(struct kimage *image, >>> + unsigned int hp_action, unsigned int cpu); >>> +#define KEXEC_CRASH_HP_REMOVE_CPU 0 >>> +#define KEXEC_CRASH_HP_ADD_CPU 1 >>> +#define KEXEC_CRASH_HP_REMOVE_MEMORY 2 >>> +#define KEXEC_CRASH_HP_ADD_MEMORY 3 >>> +#endif /* CONFIG_CRASH_HOTPLUG */ >>> + >>> /* kexec interface functions */ >>> extern void machine_kexec(struct kimage *image); >>> extern int machine_kexec_prepare(struct kimage *image); >>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >>> index 256cf6db573c..ecf746243ab2 100644 >>> --- a/kernel/crash_core.c >>> +++ b/kernel/crash_core.c >>> @@ -9,12 +9,17 @@ >>> #include <linux/init.h> >>> #include <linux/utsname.h> >>> #include <linux/vmalloc.h> >>> +#include <linux/highmem.h> >>> +#include <linux/memory.h> >>> +#include <linux/cpuhotplug.h> >>> #include <asm/page.h> >>> #include <asm/sections.h> >>> #include <crypto/sha1.h> >>> +#include "kexec_internal.h" >>> + >>> /* vmcoreinfo stuff */ >>> unsigned char *vmcoreinfo_data; >>> size_t vmcoreinfo_size; >>> @@ -491,3 +496,99 @@ static int __init crash_save_vmcoreinfo_init(void) >>> } >>> subsys_initcall(crash_save_vmcoreinfo_init); >>> + >>> +#ifdef CONFIG_CRASH_HOTPLUG >>> +void __weak arch_crash_hotplug_handler(struct kimage *image, >>> + unsigned int hp_action, unsigned int cpu) >>> +{ >>> + pr_warn("crash hp: %s not implemented", __func__); >>> +} >>> + >>> +static void crash_hotplug_handler(unsigned int hp_action, >>> + unsigned int cpu) >>> +{ >>> + /* Obtain lock while changing crash information */ >>> + if (!mutex_trylock(&kexec_mutex)) >>> + return; >>> + >>> + /* Check kdump is loaded */ >>> + if (kexec_crash_image) { >>> + pr_debug("crash hp: hp_action %u, cpu %u", hp_action, cpu); >>> + >>> + /* Needed in order for the segments to be updated */ >>> + arch_kexec_unprotect_crashkres(); >>> + >>> + /* Flag to differentiate between normal load and hotplug */ >>> + kexec_crash_image->hotplug_event = true; >>> + >>> + /* Now invoke arch-specific update handler */ >>> + arch_crash_hotplug_handler(kexec_crash_image, hp_action, cpu); >>> + >>> + /* No longer handling a hotplug event */ >>> + kexec_crash_image->hotplug_event = false; >>> + >>> + /* Change back to read-only */ >>> + arch_kexec_protect_crashkres(); >>> + } >>> + >>> + /* Release lock now that update complete */ >>> + mutex_unlock(&kexec_mutex); >>> +} >>> + >>> +#if defined(CONFIG_MEMORY_HOTPLUG) >>> +static int crash_memhp_notifier(struct notifier_block *nb, >>> + unsigned long val, void *v) >>> +{ >>> + struct memory_notify *mhp = v; >>> + >>> + switch (val) { >>> + case MEM_ONLINE: >>> + crash_hotplug_handler(KEXEC_CRASH_HP_ADD_MEMORY, -1U); >> We don't differentiate the memory add/remove, cpu add, except of cpu >> remove. Means the hp_action only differentiate cpu remove from the other >> action. Maybe only making two types? >> >> #define KEXEC_CRASH_HP_REMOVE_CPU 0 >> #define KEXEC_CRASH_HP_UPDATE_OTHER 1 >> > Sourabh Jain's work with PPC uses REMOVE_CPU, REMOVE_MEMORY, and > ADD_MEMORY. > Do you still want to consolidate these?
On PowerPC different actions are needed for CPU add and memory add/remove. For CPU add case only FDT is updated whereas for the memory hotplug we will be updating FDT and elfcorehdr.
Ideally, I would prefer the crash hotplug handler to report all four actions separately.
Thanks, Sourabh Jain
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