After applying "nosmt" to disable SMT threads, we are unable to enable the CPUs at a later date

Solution Unverified - Updated -

Issue

  • We disabled SMT via the nosmt kernel boot parameter, but now we are unable to re-enable the CPUs. The cpus should be able to be enabled since we didn't use the nosmt=force boot parameter.
# for IDX in {1,3,5,7}; do echo 1 > /sys/devices/system/cpu/cpu$IDX/online; done
bash: echo: write error: Operation not permitted
bash: echo: write error: Operation not permitted
bash: echo: write error: Operation not permitted
bash: echo: write error: Operation not permitted

Environment

  • Red Hat Enterprise Linux 7

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