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Date:   Mon, 9 May 2022 10:43:15 -0500
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Subject: Re: [PATCH v8 3/7] crash: add generic infrastructure for crash
 hotplug support
Content-Language: en-US
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        kexec@lists.infradead.org, ebiederm@xmission.com,
        dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de,
        mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com,
        hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com,
        robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com,
        konrad.wilk@oracle.com, boris.ostrovsky@oracle.com
References: <20220505184603.1548-1-eric.devolder@oracle.com>
 <20220505184603.1548-4-eric.devolder@oracle.com>
 <YnTKcvkCoRBxqGSW@MiWiFi-R3L-srv>
From:   Eric DeVolder <eric.devolder@oracle.com>
In-Reply-To: <YnTKcvkCoRBxqGSW@MiWiFi-R3L-srv>
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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
>>
>