Re: [PATCH v2] ppc/fadump: invoke kmsg_dump in fadump panic path

[Shirisha ganta <shirisha@linux.ibm.com>]

On Sun, 2026-04-12 at 17:00 +0530, Shivang Upadhyay wrote:
> fadump is registered in panic_notifier_list and gets triggered before
> kmsg_dump_desc() in the panic path. As a result, kmsg_dumpers such as
> pstore are not executed during fadump crashes.
> 
> This is problematic because pstore provides a critical fallback
> mechanism
> for crash analysis. When fadump fails to successfully reboot the
> system
> or capture a dump, pstore logs may be the only available information
> from
> the crashed kernel. Without invoking kmsg_dump_desc() in the fadump
> path,
> we lose this valuable diagnostic data.
> 
> Invoke kmsg_dump_desc() from the fadump panic handler, but only when
> fadump is actually registered (checked via should_fadump_crash()).
> This
> ensures kmsg_dumpers are called without duplicating the call that
> occurs
> later in panic() when fadump is not active.
> 
> The call is placed before crash_fadump() to ensure logs are captured
> before the system attempts to trigger the firmware-assisted dump.
> 
> Cc: Hari Bathini <hbathini@linux.ibm.com>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> Reported-by: Shirisha G <shirisha@linux.ibm.com>
> Suggested-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> Signed-off-by: Shivang Upadhyay <shivangu@linux.ibm.com>
> ---

Hi,
Tested this patch and dmesg-nvram file under /sys/fs/pstore is
getting updated with this patch after triggering dump with fadump

without this patch:
# ls -ltrh
total 0
-r--r--r--. 1 root root 6.5K Apr  2 06:22 dmesg-nvram-1
-r--r--r--. 1 root root 2.6K Apr 15 00:07 powerpc-common-nvram-6
-r--r--r--. 1 root root 2.1K Apr 15 00:07 rtas-nvram-1
-r--r--r--. 1 root root  688 Apr 15 00:07 powerpc-ofw-nvram-5

With this patch:
# ls -ltrh
total 0
-r--r--r--. 1 root root 6.4K Apr 15
00:36 dmesg-nvram-1
-r--r--r--. 1 root root 2.6K Apr 15 00:37 powerpc-
common-nvram-6
-r--r--r--. 1 root root 2.1K Apr 15 00:37 rtas-nvram-1
-r-
-r--r--. 1 root root  688 Apr 15 00:37 powerpc-ofw-nvram-5


Please add
below tag
Tested-by: Shirisha G <shirisha@linux.ibm.com>
> Changelog:
> 
> v2:
>   address comments from Sourabh, and sashikio-ai
>   added should_fadump_crash()
> 
> v1:
>   
> https://lore.kernel.org/all/20260407054341.308710-1-shivangu@linux.ibm.com/
> ---
>  arch/powerpc/kernel/setup-common.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/setup-common.c
> b/arch/powerpc/kernel/setup-common.c
> index b1761909c23f..87afc8003a03 100644
> --- a/arch/powerpc/kernel/setup-common.c
> +++ b/arch/powerpc/kernel/setup-common.c
> @@ -68,6 +68,7 @@
>  #include <asm/kasan.h>
>  #include <asm/mce.h>
>  #include <asm/systemcfg.h>
> +#include <linux/kmsg_dump.h>
>  
>  #include "setup.h"
>  
> @@ -744,6 +745,13 @@ static int ppc_panic_fadump_handler(struct
> notifier_block *this,
>  	 */
>  	hard_irq_disable();
>  
> +	/*
> +	 * Invoke kmsg_dump (e.g., pstore) before crash_fadump() as
> fadump
> +	 * runs before panic()'s kmsg_dump_desc() call.
> +	 */
> +	if (should_fadump_crash())
> +		kmsg_dump_desc(KMSG_DUMP_PANIC, (char *)ptr);
> +
>  	/*
>  	 * If firmware-assisted dump has been registered then trigger
>  	 * its callback and let the firmware handles everything else.