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| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2014-05-08 11:20:23 +0200 |
|---|---|---|
| committer | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2014-05-08 11:31:57 +0200 |
| commit | 005f78cd88494457ed38ce817f4e3fe5d372f0cb (patch) | |
| tree | f41fff97609ae7c98bc9841bd85b60a3aa892c08 /arch/arm64/kernel/entry.S | |
| parent | c51f92693c35c141cf7d9b7e2fcbb81128324eb4 (diff) | |
| download | blackbird-op-linux-005f78cd88494457ed38ce817f4e3fe5d372f0cb.tar.gz blackbird-op-linux-005f78cd88494457ed38ce817f4e3fe5d372f0cb.zip | |
arm64: defer reloading a task's FPSIMD state to userland resume
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>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 39ac630d83de..80464e2fb1a5 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -576,7 +576,7 @@ fast_work_pending: str x0, [sp, #S_X0] // returned x0 work_pending: tbnz x1, #TIF_NEED_RESCHED, work_resched - /* TIF_SIGPENDING or TIF_NOTIFY_RESUME case */ + /* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */ ldr x2, [sp, #S_PSTATE] mov x0, sp // 'regs' tst x2, #PSR_MODE_MASK // user mode regs? |
