Re: [PATCH] acpi/ghes: Make ghes_panic_timeout adjustable as a parameter

["Huang, Ying" <ying.huang@linux.alibaba.com>]

Borislav Petkov <bp@alien8.de> writes:

> On Tue, Dec 31, 2024 at 06:15:59PM +0800, Feng Tang wrote:
>> Thanks for the hint! IIUC, you are mentioning the set_arch_panic_timeout().
>> One thing is, most ARCHs' default timeout is 0, while in our case, the user
>> will also set 'panic=0' :), so we can't easily detect if the 0 is the user-set
>> value or the OS default one. Originally I even thought about adding a flag
>> of 'timeout_user_changed'.  Any suggestion?
>
> Ok, enough talking. Let's get concrete:
>
> From: "Borislav Petkov (AMD)" <bp@alien8.de>
> Date: Tue, 31 Dec 2024 12:03:55 +0100
> Subject: [PATCH] APEI: GHES: Have GHES honor the panic= setting
>
> The GHES driver overrides the panic= setting by rebooting the system
> after a fatal hw error has been reported. The intent being that such an
> error would be hopefully written out faster on non-volatile storage for
> later inspection.

IIUC, the hardware error will be written out on non-volatile storage at
the same time with or without ghes_panic_timeout overriding.  The
difference is that after rebooting, the error information in
non-volatile storage can be extracted and reported via UI, SNMP, or
MCTP earlier.

> However, this is not optimal when a hard-to-debug issue requires long
> time to reproduce and when that happens, the box will get rebooted after
> 30 seconds and thus destroy the whole hw context of when the error
> happened.
>
> So rip out the default GHES panic timeout and honor the global one.
>
> In the panic disabled (panic=0) case, the error will still be logged to
> dmesg for later inspection and if panic after a hw error is really
> required, then that can be controlled the usual way - use panic= on the
> cmdline or set it in the kernel .config's CONFIG_PANIC_TIMEOUT.
>
> Reported-by: Feng Tang <feng.tang@linux.alibaba.com>
> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
> ---
>  drivers/acpi/apei/ghes.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 07789f0b59bc..b72772494655 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -173,8 +173,6 @@ static struct gen_pool *ghes_estatus_pool;
>  static struct ghes_estatus_cache __rcu *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
>  static atomic_t ghes_estatus_cache_alloced;
>  
> -static int ghes_panic_timeout __read_mostly = 30;
> -
>  static void __iomem *ghes_map(u64 pfn, enum fixed_addresses fixmap_idx)
>  {
>  	phys_addr_t paddr;
> @@ -983,14 +981,16 @@ static void __ghes_panic(struct ghes *ghes,
>  			 struct acpi_hest_generic_status *estatus,
>  			 u64 buf_paddr, enum fixed_addresses fixmap_idx)
>  {
> +	const char *msg = GHES_PFX "Fatal hardware error";
> +
>  	__ghes_print_estatus(KERN_EMERG, ghes->generic, estatus);
>  
>  	ghes_clear_estatus(ghes, estatus, buf_paddr, fixmap_idx);
>  
> -	/* reboot to log the error! */
>  	if (!panic_timeout)
> -		panic_timeout = ghes_panic_timeout;
> -	panic("Fatal hardware error!");
> +		pr_emerg("%s but panic disabled\n", msg);
> +
> +	panic(msg);
>  }
>  
>  static int ghes_proc(struct ghes *ghes)

---
Best Regards,
Huang, Ying