s390/ap: Fix MAPML computation

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When the TAPQ subfunction of PQAP returns a value between 0 and 3 in the
ml field, the Principles of Operation states that the Maximum AP Message
Length (MAPML) must be 12 KB.

The previous code incorrectly calculated smaller sizes for ml values 1-2:
- ml=1: 4 KB instead of 12 KB
- ml=2: 8 KB instead of 12 KB

While no current hardware reports ml=1 or ml=2, this fix ensures correct
behavior for specification compliance and future-proofing.

The fix ensures all ml values 0-3 correctly use the 12 KB default, with
only values 4+ using the formula ml * 4096.

Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Finn Callies <fcallies@linux.ibm.com>
Acked-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

...

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Finn Callies 2026-08-05 11:29:28 +02:00 • committed by Vasily Gorbik

parent 5ddf6f12dc

commit 0de29a313c

1 changed files with 1 additions and 1 deletions

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drivers/s390/crypto/ap_card.c

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