s390/cio: Check pmcw.dnv before pmcw.ena in I/O entry points

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The device number valid (dnv) bit in the PMCW must be checked before
acting on any other PMCW fields for IO-type subchannels. A subchannel
with dnv=0 has no valid device number associated, making it meaningless
to evaluate the enabled (ena) state or issue any I/O instruction against
it.

Reported-by: William Bezenah <wbezenah@linux.ibm.com>
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Fixes: 8c58a22968 ("s390/cio: Do not unregister the subchannel based on DNV")
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

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Vineeth Vijayan 2026-09-10 11:32:02 +02:00 • committed by Heiko Carstens

parent 29d9e5835d

commit f6f2985eab

1 changed files with 12 additions and 0 deletions

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drivers/s390/cio/device_ops.c

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