Messages in this thread | | | Date | Mon, 28 Nov 2022 09:46:34 -0600 | Subject | Re: [PATCH v14 3/7] crash: add generic infrastructure for crash hotplug support | From | Eric DeVolder <> |
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On 11/24/22 21:26, Baoquan He wrote: > On 11/16/22 at 04:46pm, Eric DeVolder wrote: > ...... >> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >> index ebf46c3b8f8b..b4dbc21f9081 100644 >> --- a/include/linux/kexec.h >> +++ b/include/linux/kexec.h >> @@ -32,6 +32,7 @@ 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 */ >> @@ -374,6 +375,13 @@ struct kimage { >> struct purgatory_info purgatory_info; >> #endif >> >> +#ifdef CONFIG_CRASH_HOTPLUG > > This kernel config CRASH_HOTPLUG is added in patch 7, but we have used > it in the previous patch, not sure if this is acceptable. > I wasn't sure what to do here either. Patch 7 is the x86 arch-specific support patch, and CRASH_HOTPLUG is introduced in arch/x86/Kconfig. I did look at introducing CRASH_HOTPLUG as a generic/non-arch-specific option, but no location seemed appropriate given HOTPLUG_CPU is arch-specific and MEMORY_HOTPLUG is in mm/Kconfig.
This doesn't break bisect, but as you point out, not sure if the location in patch 7 is acceptable. I'm not really sure how to resolve the question.
eric
>> + bool hotplug_event; >> + unsigned int offlinecpu; >> + bool elfcorehdr_index_valid; >> + int elfcorehdr_index; >> +#endif >> + >> #ifdef CONFIG_IMA_KEXEC >> /* Virtual address of IMA measurement buffer for kexec syscall */ >> void *ima_buffer; >> @@ -503,6 +511,34 @@ static inline int arch_kexec_post_alloc_pages(void *vaddr, unsigned int pages, g >> static inline void arch_kexec_pre_free_pages(void *vaddr, unsigned int pages) { } >> #endif >> >> +#ifndef arch_map_crash_pages >> +/* >> + * NOTE: The addresses and sizes passed to this routine have >> + * already been fully aligned on page boundaries. There is no >> + * need for massaging the address or size. >> + */ >> +static inline void *arch_map_crash_pages(unsigned long paddr, >> + unsigned long size) >> +{ >> + if (size > 0) >> + return kmap_local_page(pfn_to_page(paddr >> PAGE_SHIFT)); >> + else >> + return NULL; >> +} >> +#endif >> + >> +#ifndef arch_unmap_crash_pages >> +static inline void arch_unmap_crash_pages(void *ptr) >> +{ >> + if (ptr) >> + kunmap_local(ptr); >> +} >> +#endif >> + >> +#ifndef arch_crash_handle_hotplug_event >> +static inline void arch_crash_handle_hotplug_event(struct kimage *image) { } >> +#endif >> + >> #else /* !CONFIG_KEXEC_CORE */ >> struct pt_regs; >> struct task_struct; >> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >> index 8c648fd5897a..4e7221226976 100644 >> --- a/kernel/crash_core.c >> +++ b/kernel/crash_core.c >> @@ -11,6 +11,8 @@ >> #include <linux/vmalloc.h> >> #include <linux/sizes.h> >> #include <linux/kexec.h> >> +#include <linux/memory.h> >> +#include <linux/cpuhotplug.h> >> >> #include <asm/page.h> >> #include <asm/sections.h> >> @@ -18,6 +20,7 @@ >> #include <crypto/sha1.h> >> >> #include "kallsyms_internal.h" >> +#include "kexec_internal.h" >> >> /* vmcoreinfo stuff */ >> unsigned char *vmcoreinfo_data; >> @@ -612,3 +615,139 @@ static int __init crash_save_vmcoreinfo_init(void) >> } >> >> subsys_initcall(crash_save_vmcoreinfo_init); >> + >> +#ifdef CONFIG_CRASH_HOTPLUG >> +#undef pr_fmt >> +#define pr_fmt(fmt) "crash hp: " fmt >> +/* >> + * To accurately reflect hot un/plug changes, the elfcorehdr (which >> + * is passed to the crash kernel via the elfcorehdr= parameter) >> + * must be updated with the new list of CPUs and memories. >> + * >> + * In order to make changes to elfcorehdr, two conditions are needed: >> + * First, the segment containing the elfcorehdr must be large enough >> + * to permit a growing number of resources; the elfcorehdr memory size >> + * is based on NR_CPUS_DEFAULT and CRASH_MAX_MEMORY_RANGES. >> + * Second, purgatory must explicitly exclude the elfcorehdr from the >> + * list of segments it checks (since the elfcorehdr changes and thus >> + * would require an update to purgatory itself to update the digest). >> + */ >> +static void handle_hotplug_event(unsigned int hp_action, unsigned int cpu) >> +{ >> + /* Obtain lock while changing crash information */ >> + if (kexec_trylock()) { >> + >> + /* Check kdump is loaded */ >> + if (kexec_crash_image) { >> + struct kimage *image = kexec_crash_image; >> + >> + if (hp_action == KEXEC_CRASH_HP_ADD_CPU || >> + hp_action == KEXEC_CRASH_HP_REMOVE_CPU) >> + pr_debug("hp_action %u, cpu %u\n", hp_action, cpu); >> + else >> + pr_debug("hp_action %u\n", hp_action); >> + >> + /* >> + * When the struct kimage is allocated, it is wiped to zero, so >> + * the elfcorehdr_index_valid defaults to false. Find the >> + * segment containing the elfcorehdr, if not already found. >> + * This works for both the kexec_load and kexec_file_load paths. >> + */ >> + if (!image->elfcorehdr_index_valid) { >> + unsigned long mem, memsz; >> + unsigned char *ptr; >> + unsigned int n; >> + >> + for (n = 0; n < image->nr_segments; n++) { >> + mem = image->segment[n].mem; >> + memsz = image->segment[n].memsz; >> + ptr = arch_map_crash_pages(mem, memsz); >> + if (ptr) { >> + /* The segment containing elfcorehdr */ >> + if (memcmp(ptr, ELFMAG, SELFMAG) == 0) { >> + image->elfcorehdr_index = (int)n; >> + image->elfcorehdr_index_valid = true; >> + } >> + } >> + arch_unmap_crash_pages((void *)ptr); >> + } >> + } >> + >> + if (!image->elfcorehdr_index_valid) { >> + pr_err("unable to locate elfcorehdr segment"); >> + goto out; >> + } >> + >> + /* Needed in order for the segments to be updated */ >> + arch_kexec_unprotect_crashkres(); >> + >> + /* Flag to differentiate between normal load and hotplug */ >> + image->hotplug_event = true; >> + >> + /* Now invoke arch-specific update handler */ >> + arch_crash_handle_hotplug_event(image); >> + >> + /* No longer handling a hotplug event */ >> + image->hotplug_event = false; >> + >> + /* Change back to read-only */ >> + arch_kexec_protect_crashkres(); >> + } >> + >> +out: >> + /* Release lock now that update complete */ >> + kexec_unlock(); >> + } >> +} >> + >> +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v) >> +{ >> + switch (val) { >> + case MEM_ONLINE: >> + handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY, >> + KEXEC_CRASH_HP_INVALID_CPU); >> + break; >> + >> + case MEM_OFFLINE: >> + handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY, >> + KEXEC_CRASH_HP_INVALID_CPU); >> + break; >> + } >> + return NOTIFY_OK; >> +} >> + >> +static struct notifier_block crash_memhp_nb = { >> + .notifier_call = crash_memhp_notifier, >> + .priority = 0 >> +}; >> + >> +static int crash_cpuhp_online(unsigned int cpu) >> +{ >> + handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu); >> + return 0; >> +} >> + >> +static int crash_cpuhp_offline(unsigned int cpu) >> +{ >> + handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu); >> + return 0; >> +} >> + >> +static int __init crash_hotplug_init(void) >> +{ >> + int result = 0; >> + >> + if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) >> + register_memory_notifier(&crash_memhp_nb); >> + >> + if (IS_ENABLED(CONFIG_HOTPLUG_CPU)) >> + result = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, >> + "crash/cpuhp", >> + crash_cpuhp_online, >> + crash_cpuhp_offline); >> + >> + return result; >> +} >> + >> +subsys_initcall(crash_hotplug_init); >> +#endif >> -- >> 2.31.1 >> >
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