Re: [PATCH v5 06/25] s390/zcrypt: Introduce cprb mempool for cca misc functions

[Holger Dengler <dengler@linux.ibm.com>]

On 15/04/2025 16:24, Harald Freudenberger wrote:
> Introduce a new module parameter "zcrypt_mempool_threshold"
> for the zcrypt module. This parameter controls the minimal
> amount of mempool items which are pre-allocated for urgent
> requests/replies and will be used with the support for the
> new xflag ZCRYPT_XFLAG_NOMEMALLOC. The default value of 5
> shall provide enough memory items to support up to 5 requests
> (and their associated reply) in parallel. The minimum value
> is 1 and is checked and in zcrypt module init().

typo: remove the second "and"

> 
> If the mempool is depleted upon one cca misc functions is called
> with the named xflag set, the function will fail with -ENOMEM
> and the caller is responsible for taking further actions.
> 
> For CCA each mempool item is 16KB, as a CCA CPRB needs to
> hold the request and the reply. The pool items only support
> requests/replies with a limit of about 8KB.
> So by default the CCA mempool consumes
>   5 * 16KB = 80KB
> 
> This is only part of an rework to support a new xflag
> ZCRYPT_XFLAG_NOMEMALLOC but not yet complete.
> 
> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
> Reviewed-by: Holger Dengler <dengler@linux.ibm.com>

--
Mit freundlichen Grüßen / Kind regards
Holger Dengler
--
IBM Systems, Linux on IBM Z Development
dengler@linux.ibm.com