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Commit 190f1ca8 authored by Ard Biesheuvel's avatar Ard Biesheuvel
Browse files

arm64: add support for kernel mode NEON in interrupt context 



This patch modifies kernel_neon_begin() and kernel_neon_end(), so
they may be called from any context. To address the case where only
a couple of registers are needed, kernel_neon_begin_partial(u32) is
introduced which takes as a parameter the number of bottom 'n' NEON
q-registers required. To mark the end of such a partial section, the
regular kernel_neon_end() should be used.

Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
parent 005f78cd

arch/arm64/include/asm/fpsimd.h

+15 −0
Original line number Diff line number Diff line
@@ -41,6 +41,17 @@ struct fpsimd_state { 
	unsigned int cpu;

};



/*

 * Struct for stacking the bottom 'n' FP/SIMD registers.

 */

struct fpsimd_partial_state {

	u32		fpsr;

	u32		fpcr;

	u32		num_regs;

	__uint128_t	vregs[32];

};





#if defined(__KERNEL__) && defined(CONFIG_COMPAT)

/* Masks for extracting the FPSR and FPCR from the FPSCR */

#define VFP_FPSCR_STAT_MASK	0xf800009f
@@ -66,6 +77,10 @@ extern void fpsimd_update_current_state(struct fpsimd_state *state); 


extern void fpsimd_flush_task_state(struct task_struct *target);



extern void fpsimd_save_partial_state(struct fpsimd_partial_state *state,

				      u32 num_regs);

extern void fpsimd_load_partial_state(struct fpsimd_partial_state *state);



#endif



#endif

arch/arm64/include/asm/fpsimdmacros.h

+35 −0
Original line number Diff line number Diff line
@@ -62,3 +62,38 @@ 
	ldr	w\tmpnr, [\state, #16 * 2 + 4]

	msr	fpcr, x\tmpnr

.endm



.altmacro

.macro fpsimd_save_partial state, numnr, tmpnr1, tmpnr2

	mrs	x\tmpnr1, fpsr

	str	w\numnr, [\state, #8]

	mrs	x\tmpnr2, fpcr

	stp	w\tmpnr1, w\tmpnr2, [\state]

	adr	x\tmpnr1, 0f

	add	\state, \state, x\numnr, lsl #4

	sub	x\tmpnr1, x\tmpnr1, x\numnr, lsl #1

	br	x\tmpnr1

	.irp	qa, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, 0

	.irp	qb, %(qa + 1)

	stp	q\qa, q\qb, [\state, # -16 * \qa - 16]

	.endr

	.endr

0:

.endm



.macro fpsimd_restore_partial state, tmpnr1, tmpnr2

	ldp	w\tmpnr1, w\tmpnr2, [\state]

	msr	fpsr, x\tmpnr1

	msr	fpcr, x\tmpnr2

	adr	x\tmpnr1, 0f

	ldr	w\tmpnr2, [\state, #8]

	add	\state, \state, x\tmpnr2, lsl #4

	sub	x\tmpnr1, x\tmpnr1, x\tmpnr2, lsl #1

	br	x\tmpnr1

	.irp	qa, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, 0

	.irp	qb, %(qa + 1)

	ldp	q\qa, q\qb, [\state, # -16 * \qa - 16]

	.endr

	.endr

0:

.endm

arch/arm64/include/asm/neon.h

+5 −1
Original line number Diff line number Diff line
@@ -8,7 +8,11 @@ 
 * published by the Free Software Foundation.

 */



#include <linux/types.h>



#define cpu_has_neon()		(1)



void kernel_neon_begin(void);

#define kernel_neon_begin()	kernel_neon_begin_partial(32)



void kernel_neon_begin_partial(u32 num_regs);

void kernel_neon_end(void);

arch/arm64/kernel/entry-fpsimd.S

+24 −0
Original line number Diff line number Diff line
@@ -41,3 +41,27 @@ 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_load_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

arch/arm64/kernel/fpsimd.c

+30 −14
Original line number Diff line number Diff line
@@ -218,30 +218,46 @@ void fpsimd_flush_task_state(struct task_struct *t) 


#ifdef CONFIG_KERNEL_MODE_NEON



static DEFINE_PER_CPU(struct fpsimd_partial_state, hardirq_fpsimdstate);

static DEFINE_PER_CPU(struct fpsimd_partial_state, softirq_fpsimdstate);



/*

 * Kernel-side NEON support functions

 */

void kernel_neon_begin(void)

void kernel_neon_begin_partial(u32 num_regs)

{

	/* Avoid using the NEON in interrupt context */

	BUG_ON(in_interrupt());

	preempt_disable();

	if (in_interrupt()) {

		struct fpsimd_partial_state *s = this_cpu_ptr(

			in_irq() ? &hardirq_fpsimdstate : &softirq_fpsimdstate);



		BUG_ON(num_regs > 32);

		fpsimd_save_partial_state(s, roundup(num_regs, 2));

	} else {

		/*

	 * Save the userland FPSIMD state if we have one and if we haven't done

	 * so already. Clear fpsimd_last_state to indicate that there is no

	 * longer userland FPSIMD state in the registers.

		 * Save the userland FPSIMD state if we have one and if we

		 * haven't done so already. Clear fpsimd_last_state to indicate

		 * that there is no longer userland FPSIMD state in the

		 * registers.

		 */

	if (current->mm && !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))

		preempt_disable();

		if (current->mm &&

		    !test_and_set_thread_flag(TIF_FOREIGN_FPSTATE))

			fpsimd_save_state(&current->thread.fpsimd_state);

		this_cpu_write(fpsimd_last_state, NULL);

	}

EXPORT_SYMBOL(kernel_neon_begin);

}

EXPORT_SYMBOL(kernel_neon_begin_partial);



void kernel_neon_end(void)

{

	if (in_interrupt()) {

		struct fpsimd_partial_state *s = this_cpu_ptr(

			in_irq() ? &hardirq_fpsimdstate : &softirq_fpsimdstate);

		fpsimd_load_partial_state(s);

	} else {

		preempt_enable();

	}

}

EXPORT_SYMBOL(kernel_neon_end);



#endif /* CONFIG_KERNEL_MODE_NEON */