Re: [PATCH v17 1/6] crash: forward memory_notify arg to arch crash hotplug handler

[Hari Bathini]

On 26/02/24 2:11 pm, Sourabh Jain wrote:

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.

Acked-by: Hari Bathini <hbath...@linux.ibm.com>

Signed-off-by: Sourabh Jain <sourabhj...@linux.ibm.com>
Acked-by: Baoquan He <b...@redhat.com>
Cc: Akhil Raj <lf32....@gmail.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Aneesh Kumar K.V <aneesh.ku...@kernel.org>
Cc: Borislav Petkov (AMD) <b...@alien8.de>
Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
Cc: Christophe Leroy <christophe.le...@csgroup.eu>
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: Dave Young <dyo...@redhat.com>
Cc: David Hildenbrand <da...@redhat.com>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: Hari Bathini <hbath...@linux.ibm.com>
Cc: Laurent Dufour <laurent.duf...@fr.ibm.com>
Cc: Mahesh Salgaonkar <mah...@linux.ibm.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Mimi Zohar <zo...@linux.ibm.com>
Cc: Naveen N Rao <nav...@kernel.org>
Cc: Oscar Salvador <osalva...@suse.de>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Valentin Schneider <vschn...@redhat.com>
Cc: Vivek Goyal <vgo...@redhat.com>
Cc: ke...@lists.infradead.org
Cc: x...@kernel.org
---
  arch/x86/include/asm/kexec.h |  2 +-
  arch/x86/kernel/crash.c      |  4 +++-
  include/linux/crash_core.h   |  2 +-
  kernel/crash_core.c          | 14 +++++++-------
  4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 91ca9a9ee3a2..cb1320ebbc23 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/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

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index e74d0c4286c1..2a682fe86352 100644
--- a/arch/x86/kernel/crash.c
+++ b/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;
diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
index d33352c2e386..647e928efee8 100644
--- a/include/linux/crash_core.h
+++ b/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);

diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 78b5dc7cee3a..70fa8111a9d6 100644
--- a/kernel/crash_core.c
+++ b/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;
  }