From cb84d11e1625aa3a081d898ca2640bf3a9ca0e96 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Thu, 3 Aug 2017 17:23:23 +0100 Subject: 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 Reviewed-by: Ard Biesheuvel Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/neon.h | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) (limited to 'arch/arm64/include/asm/neon.h') diff --git a/arch/arm64/include/asm/neon.h b/arch/arm64/include/asm/neon.h index 5368bd04fe7b..fb9d137256a6 100644 --- a/arch/arm64/include/asm/neon.h +++ b/arch/arm64/include/asm/neon.h @@ -16,9 +16,7 @@ #define cpu_has_neon() system_supports_fpsimd() -#define kernel_neon_begin() kernel_neon_begin_partial(32) - -void kernel_neon_begin_partial(u32 num_regs); +void kernel_neon_begin(void); void kernel_neon_end(void); #endif /* ! __ASM_NEON_H */ -- cgit