Re: [PATCH] s390/pai: Reduce excessive debug feature size

[Thomas Richter <tmricht@linux.ibm.com>]

On 8/25/26 11:49, Heiko Carstens wrote:
> The pai debug feature is registered with 256 areas, where each area
> contains 32 pages. This sums up to a total of 32MiB. The code does not use
> any debug exceptions, which means that 255 of those areas are never
> used. In addition all existing debug feature calls have a lower level (5)
> than the default level (3).
> 
> This in turn means that without user interaction the debug feature is
> unused.
> 
> Reduce the number of areas to 1, and also reduce the number of pages for
> the remaining area to 1. Since user interaction is required, the user can
> also increase the size of the remaining area, instead of wasting memory by
> default.
> 
> This reduces the total size of the debug feature to 4KiB.
> 
> Fixes: a3f8423622ef ("s390/pai_crypto: Add PAI crypto characteristics table for parameters")
> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
> ---
>  arch/s390/kernel/perf_pai.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/s390/kernel/perf_pai.c b/arch/s390/kernel/perf_pai.c
> index cdb8006220ca..ab76ed7ad791 100644
> --- a/arch/s390/kernel/perf_pai.c
> +++ b/arch/s390/kernel/perf_pai.c
> @@ -1221,7 +1221,7 @@ static int __init paipmu_setup(void)
>  static int __init pai_init(void)
>  {
>  	/* Setup s390dbf facility */
> -	paidbg = debug_register("pai", 32, 256, 128);
> +	paidbg = debug_register("pai", 1, 1, 128);
>  	if (!paidbg) {
>  		pr_err("Registration of s390dbf pai failed\n");
>  		return -ENOMEM;

Reviewed-by: Thomas Richter <tmricht@linux.ibm.com>

-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
IBM Deutschland Research & Development GmbH

Vorsitzender des Aufsichtsrats: Wolfgang Wendt

Geschäftsführung: David Faller

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