forked from Minki/linux
cb84d11e16
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>
77 lines
2.0 KiB
C
77 lines
2.0 KiB
C
/*
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* Copyright (C) 2012 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef __ASM_FP_H
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#define __ASM_FP_H
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#include <asm/ptrace.h>
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#ifndef __ASSEMBLY__
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/*
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* FP/SIMD storage area has:
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* - FPSR and FPCR
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* - 32 128-bit data registers
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*
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* Note that user_fpsimd forms a prefix of this structure, which is
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* relied upon in the ptrace FP/SIMD accessors.
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*/
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struct fpsimd_state {
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union {
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struct user_fpsimd_state user_fpsimd;
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struct {
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__uint128_t vregs[32];
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u32 fpsr;
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u32 fpcr;
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};
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};
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/* the id of the last cpu to have restored this state */
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unsigned int cpu;
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};
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#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
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/* Masks for extracting the FPSR and FPCR from the FPSCR */
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#define VFP_FPSCR_STAT_MASK 0xf800009f
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#define VFP_FPSCR_CTRL_MASK 0x07f79f00
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/*
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* The VFP state has 32x64-bit registers and a single 32-bit
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* control/status register.
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*/
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#define VFP_STATE_SIZE ((32 * 8) + 4)
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#endif
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struct task_struct;
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extern void fpsimd_save_state(struct fpsimd_state *state);
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extern void fpsimd_load_state(struct fpsimd_state *state);
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extern void fpsimd_thread_switch(struct task_struct *next);
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extern void fpsimd_flush_thread(void);
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extern void fpsimd_preserve_current_state(void);
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extern void fpsimd_restore_current_state(void);
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extern void fpsimd_update_current_state(struct fpsimd_state *state);
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extern void fpsimd_flush_task_state(struct task_struct *target);
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/* For use by EFI runtime services calls only */
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extern void __efi_fpsimd_begin(void);
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extern void __efi_fpsimd_end(void);
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#endif
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#endif
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