arm64: fix bug for reloading FPSIMD state after CPU hotplug.
authorJanet Liu <janet.liu@spreadtrum.com>
Thu, 11 Jun 2015 04:02:45 +0000 (12:02 +0800)
committerCatalin Marinas <catalin.marinas@arm.com>
Thu, 11 Jun 2015 16:08:11 +0000 (17:08 +0100)
commit32365e64a20edcc783137ad17fdd951ab814a2fe
tree68245a2a02b0c86ee09bd6640032018f87d2b6aa
parent6eb6c80187c55b7f95683bc6502dccac54b95b92
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 <janet.liu@spreadtrum.com>
Signed-off-by: Xiongshan An <xiongshan.an@spreadtrum.com>
Signed-off-by: Chunyan Zhang <chunyan.zhang@spreadtrum.com>
[catalin.marinas@arm.com: some mostly cosmetic clean-ups]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
arch/arm64/kernel/fpsimd.c