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

Eric DeVolder
2022-05-09T15:44:03Z

On 5/6/22 02:12, Baoquan He wrote:
> 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.

Ahh, I missed that. At one point in time we moved map_crash_pages() into this file, which brought
highmem.h along with it. But we have since moved map_crash_pages() into x86/crash.c. And I missed
eliminating highmem.h at that time.

I have removed this for v9.

eric

>
>> +#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
>>
>