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arm64: Floating point and SIMD 

This patch adds support for FP/ASIMD register bank saving and restoring
during context switch and FP exception handling to generate SIGFPE.
There are 32 128-bit registers and the context switching is currently
done non-lazily. Benchmarks on real hardware are required before
implementing lazy FP state saving/restoring.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
This commit is contained in:
Catalin Marinas 2012-03-05 11:49:32 +00:00
parent 3dd681d944
commit 53631b54c8
3 changed files with 250 additions and 0 deletions
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64
arch/arm64/include/asm/fpsimd.h Normal file
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/*
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ASM_FP_H
#define __ASM_FP_H
#include <asm/ptrace.h>
#ifndef __ASSEMBLY__
/*
* FP/SIMD storage area has:
* - FPSR and FPCR
* - 32 128-bit data registers
*
* Note that user_fp forms a prefix of this structure, which is relied
* upon in the ptrace FP/SIMD accessors. struct user_fpsimd_state must
* form a prefix of struct fpsimd_state.
*/
struct fpsimd_state {
union {
struct user_fpsimd_state user_fpsimd;
struct {
__uint128_t vregs[32];
u32 fpsr;
u32 fpcr;
};
};
};
#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
/* Masks for extracting the FPSR and FPCR from the FPSCR */
#define VFP_FPSCR_STAT_MASK 0xf800009f
#define VFP_FPSCR_CTRL_MASK 0x07f79f00
/*
* The VFP state has 32x64-bit registers and a single 32-bit
* control/status register.
*/
#define VFP_STATE_SIZE ((32 * 8) + 4)
#endif
struct task_struct;
extern void fpsimd_save_state(struct fpsimd_state *state);
extern void fpsimd_load_state(struct fpsimd_state *state);
extern void fpsimd_thread_switch(struct task_struct *next);
extern void fpsimd_flush_thread(void);
#endif
#endif

80
arch/arm64/kernel/entry-fpsimd.S Normal file
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/*
* FP/SIMD state saving and restoring
*
* Copyright (C) 2012 ARM Ltd.
* Author: Catalin Marinas <catalin.marinas@arm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
/*
* Save the FP registers.
*
* x0 - pointer to struct fpsimd_state
*/
ENTRY(fpsimd_save_state)
stp q0, q1, [x0, #16 * 0]
stp q2, q3, [x0, #16 * 2]
stp q4, q5, [x0, #16 * 4]
stp q6, q7, [x0, #16 * 6]
stp q8, q9, [x0, #16 * 8]
stp q10, q11, [x0, #16 * 10]
stp q12, q13, [x0, #16 * 12]
stp q14, q15, [x0, #16 * 14]
stp q16, q17, [x0, #16 * 16]
stp q18, q19, [x0, #16 * 18]
stp q20, q21, [x0, #16 * 20]
stp q22, q23, [x0, #16 * 22]
stp q24, q25, [x0, #16 * 24]
stp q26, q27, [x0, #16 * 26]
stp q28, q29, [x0, #16 * 28]
stp q30, q31, [x0, #16 * 30]!
mrs x8, fpsr
str w8, [x0, #16 * 2]
mrs x8, fpcr
str w8, [x0, #16 * 2 + 4]
ret
ENDPROC(fpsimd_save_state)
/*
* Load the FP registers.
*
* x0 - pointer to struct fpsimd_state
*/
ENTRY(fpsimd_load_state)
ldp q0, q1, [x0, #16 * 0]
ldp q2, q3, [x0, #16 * 2]
ldp q4, q5, [x0, #16 * 4]
ldp q6, q7, [x0, #16 * 6]
ldp q8, q9, [x0, #16 * 8]
ldp q10, q11, [x0, #16 * 10]
ldp q12, q13, [x0, #16 * 12]
ldp q14, q15, [x0, #16 * 14]
ldp q16, q17, [x0, #16 * 16]
ldp q18, q19, [x0, #16 * 18]
ldp q20, q21, [x0, #16 * 20]
ldp q22, q23, [x0, #16 * 22]
ldp q24, q25, [x0, #16 * 24]
ldp q26, q27, [x0, #16 * 26]
ldp q28, q29, [x0, #16 * 28]
ldp q30, q31, [x0, #16 * 30]!
ldr w8, [x0, #16 * 2]
ldr w9, [x0, #16 * 2 + 4]
msr fpsr, x8
msr fpcr, x9
ret
ENDPROC(fpsimd_load_state)

106
arch/arm64/kernel/fpsimd.c Normal file
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/*
* FP/SIMD context switching and fault handling
*
* Copyright (C) 2012 ARM Ltd.
* Author: Catalin Marinas <catalin.marinas@arm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <asm/fpsimd.h>
#include <asm/cputype.h>
#define FPEXC_IOF (1 << 0)
#define FPEXC_DZF (1 << 1)
#define FPEXC_OFF (1 << 2)
#define FPEXC_UFF (1 << 3)
#define FPEXC_IXF (1 << 4)
#define FPEXC_IDF (1 << 7)
/*
* Trapped FP/ASIMD access.
*/
void do_fpsimd_acc(unsigned int esr, struct pt_regs *regs)
{
/* TODO: implement lazy context saving/restoring */
WARN_ON(1);
}
/*
* Raise a SIGFPE for the current process.
*/
void do_fpsimd_exc(unsigned int esr, struct pt_regs *regs)
{
siginfo_t info;
unsigned int si_code = 0;
if (esr & FPEXC_IOF)
si_code = FPE_FLTINV;
else if (esr & FPEXC_DZF)
si_code = FPE_FLTDIV;
else if (esr & FPEXC_OFF)
si_code = FPE_FLTOVF;
else if (esr & FPEXC_UFF)
si_code = FPE_FLTUND;
else if (esr & FPEXC_IXF)
si_code = FPE_FLTRES;
memset(&info, 0, sizeof(info));
info.si_signo = SIGFPE;
info.si_code = si_code;
info.si_addr = (void __user *)instruction_pointer(regs);
send_sig_info(SIGFPE, &info, current);
}
void fpsimd_thread_switch(struct task_struct *next)
{
/* check if not kernel threads */
if (current->mm)
fpsimd_save_state(&current->thread.fpsimd_state);
if (next->mm)
fpsimd_load_state(&next->thread.fpsimd_state);
}
void fpsimd_flush_thread(void)
{
memset(&current->thread.fpsimd_state, 0, sizeof(struct fpsimd_state));
fpsimd_load_state(&current->thread.fpsimd_state);
}
/*
* FP/SIMD support code initialisation.
*/
static int __init fpsimd_init(void)
{
u64 pfr = read_cpuid(ID_AA64PFR0_EL1);
if (pfr & (0xf << 16)) {
pr_notice("Floating-point is not implemented\n");
return 0;
}
elf_hwcap |= HWCAP_FP;
if (pfr & (0xf << 20))
pr_notice("Advanced SIMD is not implemented\n");
else
elf_hwcap |= HWCAP_ASIMD;
return 0;
}
late_initcall(fpsimd_init);