From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 0D3A21A0336 for ; Mon, 15 Feb 2016 16:09:24 +1100 (AEDT) Received: from e23smtp08.au.ibm.com (e23smtp08.au.ibm.com [202.81.31.141]) (using TLSv1 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 85A5A140BFF for ; Mon, 15 Feb 2016 16:09:23 +1100 (AEDT) Received: from localhost by e23smtp08.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 15 Feb 2016 15:09:23 +1000 Received: from d23relay08.au.ibm.com (d23relay08.au.ibm.com [9.185.71.33]) by d23dlp01.au.ibm.com (Postfix) with ESMTP id C26C92CE8057 for ; Mon, 15 Feb 2016 16:09:19 +1100 (EST) Received: from d23av03.au.ibm.com (d23av03.au.ibm.com [9.190.234.97]) by d23relay08.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u1F59Brf000408 for ; Mon, 15 Feb 2016 16:09:19 +1100 Received: from d23av03.au.ibm.com (localhost [127.0.0.1]) by d23av03.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u1F58ljS030534 for ; Mon, 15 Feb 2016 16:08:47 +1100 From: Cyril Bur To: linuxppc-dev@ozlabs.org Cc: mikey@neuling.org, anton@samba.org Subject: [PATCH v4 7/9] powerpc: Add the ability to save FPU without giving it up Date: Mon, 15 Feb 2016 16:07:28 +1100 Message-Id: <1455512850-2543-8-git-send-email-cyrilbur@gmail.com> In-Reply-To: <1455512850-2543-1-git-send-email-cyrilbur@gmail.com> References: <1455512850-2543-1-git-send-email-cyrilbur@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , This patch adds the ability to be able to save the FPU registers to the thread struct without giving up (disabling the facility) next time the process returns to userspace. This patch optimises the thread copy path (as a result of a fork() or clone()) so that the parent thread can return to userspace with hot registers avoiding a possibly pointless reload of FPU register state. Signed-off-by: Cyril Bur --- arch/powerpc/include/asm/switch_to.h | 3 ++- arch/powerpc/kernel/fpu.S | 21 ++++----------------- arch/powerpc/kernel/process.c | 12 +++++++++++- 3 files changed, 17 insertions(+), 19 deletions(-) diff --git a/arch/powerpc/include/asm/switch_to.h b/arch/powerpc/include/asm/switch_to.h index 3690041..6a201e8 100644 --- a/arch/powerpc/include/asm/switch_to.h +++ b/arch/powerpc/include/asm/switch_to.h @@ -28,13 +28,14 @@ extern void giveup_all(struct task_struct *); extern void enable_kernel_fp(void); extern void flush_fp_to_thread(struct task_struct *); extern void giveup_fpu(struct task_struct *); -extern void __giveup_fpu(struct task_struct *); +extern void save_fpu(struct task_struct *); static inline void disable_kernel_fp(void) { msr_check_and_clear(MSR_FP); } #else static inline void __giveup_fpu(struct task_struct *t) { } +static inline void save_fpu(struct task_struct *t) { } static inline void flush_fp_to_thread(struct task_struct *t) { } #endif diff --git a/arch/powerpc/kernel/fpu.S b/arch/powerpc/kernel/fpu.S index b063524..15da2b5 100644 --- a/arch/powerpc/kernel/fpu.S +++ b/arch/powerpc/kernel/fpu.S @@ -143,33 +143,20 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX) blr /* - * __giveup_fpu(tsk) - * Disable FP for the task given as the argument, - * and save the floating-point registers in its thread_struct. + * save_fpu(tsk) + * Save the floating-point registers in its thread_struct. * Enables the FPU for use in the kernel on return. */ -_GLOBAL(__giveup_fpu) +_GLOBAL(save_fpu) addi r3,r3,THREAD /* want THREAD of task */ PPC_LL r6,THREAD_FPSAVEAREA(r3) PPC_LL r5,PT_REGS(r3) PPC_LCMPI 0,r6,0 bne 2f addi r6,r3,THREAD_FPSTATE -2: PPC_LCMPI 0,r5,0 - SAVE_32FPVSRS(0, R4, R6) +2: SAVE_32FPVSRS(0, R4, R6) mffs fr0 stfd fr0,FPSTATE_FPSCR(r6) - beq 1f - PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5) - li r3,MSR_FP|MSR_FE0|MSR_FE1 -#ifdef CONFIG_VSX -BEGIN_FTR_SECTION - oris r3,r3,MSR_VSX@h -END_FTR_SECTION_IFSET(CPU_FTR_VSX) -#endif - andc r4,r4,r3 /* disable FP for previous task */ - PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5) -1: blr /* diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 29da07f..a7e5061 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -133,6 +133,16 @@ void __msr_check_and_clear(unsigned long bits) EXPORT_SYMBOL(__msr_check_and_clear); #ifdef CONFIG_PPC_FPU +void __giveup_fpu(struct task_struct *tsk) +{ + save_fpu(tsk); + tsk->thread.regs->msr &= ~MSR_FP; +#ifdef CONFIG_VSX + if (cpu_has_feature(CPU_FTR_VSX)) + tsk->thread.regs->msr &= ~MSR_VSX; +#endif +} + void giveup_fpu(struct task_struct *tsk) { check_if_tm_restore_required(tsk); @@ -459,7 +469,7 @@ void save_all(struct task_struct *tsk) msr_check_and_set(msr_all_available); if (usermsr & MSR_FP) - __giveup_fpu(tsk); + save_fpu(tsk); if (usermsr & MSR_VEC) __giveup_altivec(tsk); -- 2.7.1