x86/cpu/topology: Make primary thread mask available with SMP=n

Browse source

cpu_primary_thread_mask is only defined when CONFIG_SMP=y. However, even
in UP kernels there is always exactly one CPU, which can reasonably be
treated as the primary thread.

Historically, topology_is_primary_thread() always returned true with
CONFIG_SMP=n. A recent commit:

  4b455f5994 ("cpu/SMT: Provide a default topology_is_primary_thread()")

replaced it with a generic implementation with the note:

  "When disabling SMT, the primary thread of the SMT will remain
   enabled/active. Architectures that have a special primary thread (e.g.
   x86) need to override this function. ..."

For consistency and clarity, make the primary thread mask available
regardless of SMP, similar to cpu_possible_mask and cpu_present_mask.

Move __cpu_primary_thread_mask into common code to prevent build issues.
Let cpu_mark_primary_thread() configure the mask even for UP kernels,
alongside other masks. Then, topology_is_primary_thread() can
consistently reference it.

Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20250320234104.8288-1-chang.seok.bae@intel.com

...

This commit is contained in:

Chang S. Bae 2025-09-21 15:48:35 -07:00 • committed by Borislav Petkov (AMD)

parent 3a86608788

commit ed44a5625f

4 changed files with 9 additions and 13 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

12

arch/x86/include/asm/topology.h

View file

4

arch/x86/kernel/cpu/topology.c

View file

3

arch/x86/kernel/cpu/topology_common.c

View file

3

arch/x86/kernel/smpboot.c

View file