s390/smp: Fix fallback CPU detection

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[ Upstream commit 07a75d08cf ]

In case SCLP CPU detection does not work a fallback mechanism using SIGP is
in place. Since a cleanup this does not work correctly anymore: new CPUs
are only considered if their type matches the boot CPU.

Before the cleanup the information if a CPU type should be considered was
also part of a structure generated by the fallback mechanism and indicated
that a CPU type should not be considered when adding CPUs.

Since the rework a global SCLP state is used instead. If the global SCLP
state indicates that the CPU type should be considered and the fallback
mechanism is used, there may be a mismatch with CPU types if CPUs are
added. This can lead to a system with only a single CPU even tough there
are many more CPUs.

Address this by simply copying the boot cpu type into the generated data
structure from the fallback mechanism.

Reported-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Fixes: d08d94306e ("s390/smp: cleanup core vs. cpu in the SCLP interface")
Reviewed-by: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Heiko Carstens 2025-10-20 16:17:54 +02:00 • committed by Greg Kroah-Hartman

parent 097c870b91

commit ecb0b9f925

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arch/s390/kernel/smp.c

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