Re: [PATCH v3 2/2] s390/ap: Cap AP maximum message size adjustable via module parameter

[sashiko-bot@kernel.org]

> With AP bus now supporting the new APMLM field with PQAP/TAPQ the AP
> max message size could be raised up to 960KB. As this amount of memory
> is tried to get allocated on each AP request/reply it would quickly
> cause some memory problems.
> 
> Introduce a reasonable default upper limit
> AP_DEFAULT_MAX_MSG_SIZE_LIMIT (72KB) and expose it via a read-only
> module parameter 'max_msg_size_limit'. When creating an AP card, clip
> the calculated AP max message size from the hardware info fetched via
> PQAP/TAPQ to this upper limit and log a debug feature warning
> (AP_DBF_WARN) if the card's reported limit exceeds it.
> 
> Also define some lower limit AP_MIN_MSG_SIZE (12KB) and ensure during
> module init that a user-supplied max_msg_size_limit parameter is not
> lower than this minimum, adjusting it with a warning if necessary.
> 
> Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261013134422.64155-1-freude@linux.ibm.com?part=2