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

[Eric DeVolder]

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