Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751773Ab3I0Lfn (ORCPT ); Fri, 27 Sep 2013 07:35:43 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:45097 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605Ab3I0Lf0 (ORCPT ); Fri, 27 Sep 2013 07:35:26 -0400 Date: Fri, 27 Sep 2013 12:35:07 +0100 From: Catalin Marinas To: Jiang Liu 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 Message-ID: <20130927113507.GC11063@MacBook-Pro.local> References: <1380269087-8520-1-git-send-email-liuj97@gmail.com> <1380269087-8520-3-git-send-email-liuj97@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1380269087-8520-3-git-send-email-liuj97@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2418 Lines: 70 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. > } > > @@ -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. > /* 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. -- Catalin -- 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/