From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1261AC282C3 for ; Thu, 24 Jan 2019 11:17:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D3E7521872 for ; Thu, 24 Jan 2019 11:17:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="RvF1AaqA" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727740AbfAXLRV (ORCPT ); Thu, 24 Jan 2019 06:17:21 -0500 Received: from mail.skyhub.de ([5.9.137.197]:41324 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726053AbfAXLRV (ORCPT ); Thu, 24 Jan 2019 06:17:21 -0500 Received: from zn.tnic (p200300EC2BCBCF00857058CDE16DF962.dip0.t-ipconnect.de [IPv6:2003:ec:2bcb:cf00:8570:58cd:e16d:f962]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id D76021EC0242; Thu, 24 Jan 2019 12:17:19 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1548328640; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=R/KSM/VoEYI/MPnLijAH75DGL4jqkkOcKozx0d7kIps=; b=RvF1AaqAvVlYTEzHp2XA4OzKE3LititkJnlIBIDtLYU30kdobfCv1/kCjidMnh4MYQ9+4g DlD8UGp8PT+MrwU2dmnHJwqriLaJMBKgZ3T2GvGkS5F7lia2OFV+fwM5GVbPDlmOTVRtjb fKYUEESgQ2Lu47Ff1w5Mds/j3xrDmbg= Date: Thu, 24 Jan 2019 12:17:14 +0100 From: Borislav Petkov To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen Subject: Re: [PATCH 06/22] x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe() Message-ID: <20190124111714.GA11554@zn.tnic> References: <20190109114744.10936-1-bigeasy@linutronix.de> <20190109114744.10936-7-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190109114744.10936-7-bigeasy@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 09, 2019 at 12:47:28PM +0100, Sebastian Andrzej Siewior wrote: > Why does copy_fpstate_to_sigframe() do copy_fxregs_to_kernel() in the > ia32_fxstate case? I don't know. It just does. > Maybe it was required at some point, maybe it was added by accident and > nobody noticed it because it makes no difference. So 72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels") talks about some exclusion of legacy fsave state. > In copy_fpstate_to_sigframe() we stash the FPU state into the task's > stackframe. Then the CPU's FPU registers (and its fpu->state) are > cleared (handle_signal() does fpu__clear()). So that fpu__clear() name is not optimal. It should be fpu__reinitialize() or so. The comment above it says so too: /* * Clear the FPU state back to init state. > So it makes *no* difference > what happens to fpu->state after copy_fpregs_to_sigframe(). > > Remove copy_fxregs_to_kernel() since it does not matter what it does and > save a few cycles. > > Signed-off-by: Sebastian Andrzej Siewior > --- > arch/x86/kernel/fpu/signal.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > index c136a4327659d..047390a45e016 100644 > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -174,9 +174,6 @@ int copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) > /* Save the live register state to the user directly. */ > if (copy_fpregs_to_sigframe(buf_fx)) > return -1; > - /* Update the thread's fxstate to save the fsave header. */ > - if (ia32_fxstate) > - copy_fxregs_to_kernel(fpu); Need to get rid of that local "fpu" var too: arch/x86/kernel/fpu/signal.c: In function ‘copy_fpstate_to_sigframe’: arch/x86/kernel/fpu/signal.c:159:14: warning: unused variable ‘fpu’ [-Wunused-variable] struct fpu *fpu = ¤t->thread.fpu; ^~~ > /* Save the fsave header for the 32-bit frames. */ > if ((ia32_fxstate || !use_fxsr()) && save_fsave_header(tsk, buf)) > -- > 2.20.1 > -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.