Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753525Ab3I0NUO (ORCPT ); Fri, 27 Sep 2013 09:20:14 -0400 Received: from mail-pb0-f53.google.com ([209.85.160.53]:44015 "EHLO mail-pb0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751164Ab3I0NUM (ORCPT ); Fri, 27 Sep 2013 09:20:12 -0400 Message-ID: <52458604.7030902@gmail.com> Date: Fri, 27 Sep 2013 21:20:04 +0800 From: Jiang Liu User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Catalin Marinas CC: Will Deacon , Jiang Liu , Ard Biesheuvel , Al Viro , Andrew Morton , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: Re: [RFT PATCH v1 2/7] arm64: restore FPSIMD to default state for kernel and signal contexts References: <1380269087-8520-1-git-send-email-liuj97@gmail.com> <1380269087-8520-3-git-send-email-liuj97@gmail.com> <20130927113507.GC11063@MacBook-Pro.local> In-Reply-To: <20130927113507.GC11063@MacBook-Pro.local> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2588 Lines: 74 On 09/27/2013 07:35 PM, Catalin Marinas wrote: > On Fri, Sep 27, 2013 at 09:04:42AM +0100, Jiang Liu wrote: >> diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c >> index bb785d2..12a25e5 100644 >> --- a/arch/arm64/kernel/fpsimd.c >> +++ b/arch/arm64/kernel/fpsimd.c >> @@ -80,9 +80,14 @@ void fpsimd_thread_switch(struct task_struct *next) >> >> void fpsimd_flush_thread(void) >> { >> + struct fpsimd_state *state = ¤t->thread.fpsimd_state; >> + >> preempt_disable(); >> - memset(¤t->thread.fpsimd_state, 0, sizeof(struct fpsimd_state)); >> - fpsimd_load_state(¤t->thread.fpsimd_state); >> + memset(state, 0, sizeof(struct fpsimd_state)); >> +#if (AARCH64_FPCR_DEFAULT_VAL != 0) >> + state->fpcr = AARCH64_FPCR_DEFAULT_VAL; >> +#endif >> + fpsimd_load_state(state); >> preempt_enable(); > > We can leave this to 0 as the default for user. Glibc already programs > this register. OK, will drop it. > >> } >> >> @@ -99,6 +104,8 @@ void kernel_neon_begin(void) >> >> if (current->mm) >> fpsimd_save_state(¤t->thread.fpsimd_state); >> + >> + fpsimd_init_hw_state(); > > This function should indeed do some initialisation rather than relying > on whatever the user set for FPCR. > >> diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c >> index 890a591..6d80612 100644 >> --- a/arch/arm64/kernel/signal.c >> +++ b/arch/arm64/kernel/signal.c >> @@ -52,6 +52,7 @@ static int preserve_fpsimd_context(struct fpsimd_context __user *ctx) >> >> /* dump the hardware registers to the fpsimd_state structure */ >> fpsimd_save_state(fpsimd); >> + fpsimd_init_hw_state(); > > Here I think we need to leave the default user setting for fpcr as > decided by glibc (or libgcc) when an application starts. OK, will keep FPCR and clear FPSR. > >> /* copy the FP and status/control registers */ >> err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs)); >> diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c >> index e393174..cb2cb41 100644 >> --- a/arch/arm64/kernel/signal32.c >> +++ b/arch/arm64/kernel/signal32.c >> @@ -248,6 +248,7 @@ static int compat_preserve_vfp_context(struct compat_vfp_sigframe __user *frame) >> * in AArch32. >> */ >> fpsimd_save_state(fpsimd); >> + fpsimd_init_hw_state(); > > Same here. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/