Re: [PATCH v8 3/7] crash: add generic infrastructure for crash hotplug support

Baoquan He
2022-05-06T07:13:25Z

On 05/05/22 at 02:45pm, Eric DeVolder wrote:
......
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 256cf6db573c..f197af50def6 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>

Wondering where highmem.h is needed. Just curious.

> +#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 +496,90 @@ static int __init crash_save_vmcoreinfo_init(void)
> }
>
> subsys_initcall(crash_save_vmcoreinfo_init);
> +
> +#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
> +void __weak arch_crash_handle_hotplug_event(struct kimage *image,
> + unsigned int hp_action, unsigned int cpu)
> +{
> + WARN(1, "crash hotplug handler not implemented");
> +}
> +
> +static void handle_hotplug_event(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_handle_hotplug_event(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);
> +}
> +
> +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, 0);
> + break;
> +
> + case MEM_OFFLINE:
> + handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY, 0);
> + 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
> --
> 2.27.0
>