arm64: defer reloading a task's FPSIMD state to userland resume

Browse source

If a task gets scheduled out and back in again and nothing has touched
its FPSIMD state in the mean time, there is really no reason to reload
it from memory. Similarly, repeated calls to kernel_neon_begin() and
kernel_neon_end() will preserve and restore the FPSIMD state every time.

This patch defers the FPSIMD state restore to the last possible moment,
i.e., right before the task returns to userland. If a task does not return to
userland at all (for any reason), the existing FPSIMD state is preserved
and may be reused by the owning task if it gets scheduled in again on the
same CPU.

This patch adds two more functions to abstract away from straight FPSIMD
register file saves and restores:
- fpsimd_restore_current_state -> ensure current's FPSIMD state is loaded
- fpsimd_flush_task_state -> invalidate live copies of a task's FPSIMD state

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

...

This commit is contained in:

Ard Biesheuvel 2014-05-08 11:20:23 +02:00

parent c51f92693c

commit 005f78cd88

6 changed files with 143 additions and 18 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

5

arch/arm64/include/asm/fpsimd.h

View file

4

arch/arm64/include/asm/thread_info.h

View file

2

arch/arm64/kernel/entry.S

View file

142

arch/arm64/kernel/fpsimd.c

View file

2

arch/arm64/kernel/ptrace.c

View file

4

arch/arm64/kernel/signal.c

View file