crash: forward memory_notify arg to arch crash hotplug handler

In the event of memory hotplug or online/offline events, the crash
memory hotplug notifier `crash_memhp_notifier()` receives a
`memory_notify` object but doesn't forward that object to the
generic and architecture-specific crash hotplug handler.

The `memory_notify` object contains the starting PFN (Page Frame Number)
and the number of pages in the hot-removed memory. This information is
necessary for architectures like PowerPC to update/recreate the kdump
image, specifically `elfcorehdr`.

So update the function signature of `crash_handle_hotplug_event()` and
`arch_crash_handle_hotplug_event()` to accept the `memory_notify` object
as an argument from crash memory hotplug notifier.

Since no such object is available in the case of CPU hotplug event, the
crash CPU hotplug notifier `crash_cpuhp_online()` passes NULL to the
crash hotplug handler.
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240326055413.186534-2-sourabhjain@linux.ibm.com

arch/x86/include/asm/kexec.h

@@ -207,7 +207,7 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image);
 extern void kdump_nmi_shootdown_cpus(void);
 
 #ifdef CONFIG_CRASH_HOTPLUG
-void arch_crash_handle_hotplug_event(struct kimage *image);
+void arch_crash_handle_hotplug_event(struct kimage *image, void *arg);
 #define arch_crash_handle_hotplug_event arch_crash_handle_hotplug_event
 
 #ifdef CONFIG_HOTPLUG_CPU

arch/x86/kernel/crash.c

@@ -432,10 +432,12 @@ unsigned int arch_crash_get_elfcorehdr_size(void)
 /**
  * arch_crash_handle_hotplug_event() - Handle hotplug elfcorehdr changes
  * @image: a pointer to kexec_crash_image
+ * @arg: struct memory_notify handler for memory hotplug case and
+ *       NULL for CPU hotplug case.
  *
  * Prepare the new elfcorehdr and replace the existing elfcorehdr.
  */
-void arch_crash_handle_hotplug_event(struct kimage *image)
+void arch_crash_handle_hotplug_event(struct kimage *image, void *arg)
 {
 	void *elfbuf = NULL, *old_elfcorehdr;
 	unsigned long nr_mem_ranges;

include/linux/crash_core.h

@@ -37,7 +37,7 @@ static inline void arch_kexec_unprotect_crashkres(void) { }
 
 
 #ifndef arch_crash_handle_hotplug_event
-static inline void arch_crash_handle_hotplug_event(struct kimage *image) { }
+static inline void arch_crash_handle_hotplug_event(struct kimage *image, void *arg) { }
 #endif
 
 int crash_check_update_elfcorehdr(void);

kernel/crash_core.c

@@ -534,7 +534,7 @@ int crash_check_update_elfcorehdr(void)
  * list of segments it checks (since the elfcorehdr changes and thus
  * would require an update to purgatory itself to update the digest).
  */
-static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
+static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu, void *arg)
 {
 	struct kimage *image;
 
@@ -596,7 +596,7 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
 	image->hp_action = hp_action;
 
 	/* Now invoke arch-specific update handler */
-	arch_crash_handle_hotplug_event(image);
+	arch_crash_handle_hotplug_event(image, arg);
 
 	/* No longer handling a hotplug event */
 	image->hp_action = KEXEC_CRASH_HP_NONE;
@@ -612,17 +612,17 @@ static void crash_handle_hotplug_event(unsigned int hp_action, unsigned int cpu)
 	crash_hotplug_unlock();
 }
 
-static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
+static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *arg)
 {
 	switch (val) {
 	case MEM_ONLINE:
 		crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
-			KEXEC_CRASH_HP_INVALID_CPU);
+			KEXEC_CRASH_HP_INVALID_CPU, arg);
 		break;
 
 	case MEM_OFFLINE:
 		crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
-			KEXEC_CRASH_HP_INVALID_CPU);
+			KEXEC_CRASH_HP_INVALID_CPU, arg);
 		break;
 	}
 	return NOTIFY_OK;
@@ -635,13 +635,13 @@ static struct notifier_block crash_memhp_nb = {
 
 static int crash_cpuhp_online(unsigned int cpu)
 {
-	crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu);
+	crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_CPU, cpu, NULL);
 	return 0;
 }
 
 static int crash_cpuhp_offline(unsigned int cpu)
 {
-	crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu);
+	crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_CPU, cpu, NULL);
 	return 0;
 }