arm64: fix bug for reloading FPSIMD state after CPU hotplug.

Now FPSIMD don't handle HOTPLUG_CPU. This introduces bug after cpu down/up process.

After cpu down/up process, the FPSMID hardware register is default value, not any
process's fpsimd context. when CPU_DEAD set cpu's fpsimd_state to NULL, it will force
to load the fpsimd context for the thread, to avoid the chance to skip to load the context.
If process A is the last user process on CPU N before cpu down, and the first user process
on the same CPU N after cpu up, A's fpsimd_state.cpu is the current cpu id,
and per_cpu(fpsimd_last_state) points A's fpsimd_state, so kernel will not reload the
context during it return to user space.

Signed-off-by: Janet Liu <[email protected]>
Signed-off-by: Xiongshan An <[email protected]>
Signed-off-by: Chunyan Zhang <[email protected]>
[[email protected]: some mostly cosmetic clean-ups]
Signed-off-by: Catalin Marinas <[email protected]>

0 files changed, 0 insertions, 0 deletions