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| author | Dave Martin <Dave.Martin@arm.com> | 2017-08-03 17:23:23 +0100 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2017-08-04 15:00:57 +0100 |
| commit | cb84d11e1625aa3a081d898ca2640bf3a9ca0e96 (patch) | |
| tree | 514af7380143b4950fd3a158d5c0b0d2a90cc56b /arch/arm64/kernel/entry-fpsimd.S | |
| parent | 4328825d4fdc185d365d8e858cace8b324198a70 (diff) | |
| download | linux-stable-cb84d11e1625aa3a081d898ca2640bf3a9ca0e96.tar.gz linux-stable-cb84d11e1625aa3a081d898ca2640bf3a9ca0e96.tar.bz2 linux-stable-cb84d11e1625aa3a081d898ca2640bf3a9ca0e96.zip | |
arm64: neon: Remove support for nested or hardirq kernel-mode NEON
Support for kernel-mode NEON to be nested and/or used in hardirq
context adds significant complexity, and the benefits may be
marginal. In practice, kernel-mode NEON is not used in hardirq
context, and is rarely used in softirq context (by certain mac80211
drivers).
This patch implements an arm64 may_use_simd() function to allow
clients to check whether kernel-mode NEON is usable in the current
context, and simplifies kernel_neon_{begin,end}() to handle only
saving of the task FPSIMD state (if any). Without nesting, there
is no other state to save.
The partial fpsimd save/restore functions become redundant as a
result of these changes, so they are removed too.
The save/restore model is changed to operate directly on
task_struct without additional percpu storage. This simplifies the
code and saves a bit of memory, but means that softirqs must now be
disabled when manipulating the task fpsimd state from task context:
correspondingly, preempt_{en,dis}sable() calls are upgraded to
local_bh_{en,dis}able() as appropriate. fpsimd_thread_switch()
already runs with hardirqs disabled and so is already protected
from softirqs.
These changes should make it easier to support kernel-mode NEON in
the presence of the Scalable Vector extension in the future.
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry-fpsimd.S')
| -rw-r--r-- | arch/arm64/kernel/entry-fpsimd.S | 24 |
1 files changed, 0 insertions, 24 deletions
diff --git a/arch/arm64/kernel/entry-fpsimd.S b/arch/arm64/kernel/entry-fpsimd.S index c44a82f146b1..6a27cd6dbfa6 100644 --- a/arch/arm64/kernel/entry-fpsimd.S +++ b/arch/arm64/kernel/entry-fpsimd.S @@ -41,27 +41,3 @@ ENTRY(fpsimd_load_state) fpsimd_restore x0, 8 ret ENDPROC(fpsimd_load_state) - -#ifdef CONFIG_KERNEL_MODE_NEON - -/* - * Save the bottom n FP registers. - * - * x0 - pointer to struct fpsimd_partial_state - */ -ENTRY(fpsimd_save_partial_state) - fpsimd_save_partial x0, 1, 8, 9 - ret -ENDPROC(fpsimd_save_partial_state) - -/* - * Load the bottom n FP registers. - * - * x0 - pointer to struct fpsimd_partial_state - */ -ENTRY(fpsimd_load_partial_state) - fpsimd_restore_partial x0, 8, 9 - ret -ENDPROC(fpsimd_load_partial_state) - -#endif |