s390/ap: Fix wrong APQN fill calculation

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commit 3317785a88 upstream.

The upper limit of the firmware queue fill state for each APQN
is reported by the hwinfo.qd field. This field shows the
numbers 0-7 for 1-8 queue spaces available. But the exploiting
code assumed the real boundary is stored there and thus stoppes
queuing in messages one tick too early.

Correct the limit calculation and thus offer a boost
of 12.5% performance for high traffic on one APQN.

Fixes: d4c53ae8e4 ("s390/ap: store TAPQ hwinfo in struct ap_card")
Cc: stable@vger.kernel.org
Reported-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Ingo Franzki <ifranzki@linux.ibm.com>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Harald Freudenberger 2026-01-19 10:37:28 +01:00 • committed by Greg Kroah-Hartman

parent f609d3491a

commit e01f18c5af

2 changed files with 2 additions and 2 deletions

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2

drivers/s390/crypto/ap_card.c

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2

drivers/s390/crypto/ap_queue.c

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