x86/smp: Enforce CONFIG_HOTPLUG_CPU when SMP=y

The SMT disable 'nosmt' command line argument is not working properly when
CONFIG_HOTPLUG_CPU is disabled. The teardown of the sibling CPUs which are
required to be brought up due to the MCE issues, cannot work. The CPUs are
then kept in a half dead state.

As the 'nosmt' functionality has become popular due to the speculative
hardware vulnerabilities, the half torn down state is not a proper solution
to the problem.

Enforce CONFIG_HOTPLUG_CPU=y when SMP is enabled so the full operation is
possible.

Reported-by: Tianyu Lan <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Cc: Konrad Wilk <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Mukesh Ojha <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Micheal Kelley <[email protected]>
Cc: "K. Y. Srinivasan" <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: K. Y. Srinivasan <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

0 files changed, 0 insertions, 0 deletions