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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 898F0C433E0 for ; Tue, 19 Jan 2021 19:37:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E0A423104 for ; Tue, 19 Jan 2021 19:37:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730053AbhASThG (ORCPT ); Tue, 19 Jan 2021 14:37:06 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729879AbhASTfq (ORCPT ); Tue, 19 Jan 2021 14:35:46 -0500 Received: from mail-pf1-x42d.google.com (mail-pf1-x42d.google.com [IPv6:2607:f8b0:4864:20::42d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F402C061757 for ; Tue, 19 Jan 2021 11:35:05 -0800 (PST) Received: by mail-pf1-x42d.google.com with SMTP id b3so12927139pft.3 for ; Tue, 19 Jan 2021 11:35:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=eXqV9fARKuqk4sDqyWfCKvyY10Fzq1Iziw7iD+TDihI=; b=HMXEgmC8wQCFb/kC8Erg3nYF6JeRPUiTGjxGTsTdjXz5Xh79WL1qzUL4KxKlHK7pxQ 8GNXaa4VhFTwE6LdIYJ0aPxHNBGjLwDc8ZsdKAdNKBjGb7avxVH8uU0MgoIwMIckg107 qbRTSJBzkVI3Cluys8+xngZ70aho0F5XQB7VY6MLe0oq0bpQQAkOmccq+zDYJGSvD+nR vh8VeCXBSc+xlt+nEWFh59JTeFotScDAQ/3wc+WCwVRvwdesI/C3Jq9D6Z3CKi/rlqD1 CYZfDrPenf579MvMlyS9AKIBF6fJqIGnlz8+lpLPU1QJWU1PIBLROJdu7z2ctQVoKeAk mWQg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=eXqV9fARKuqk4sDqyWfCKvyY10Fzq1Iziw7iD+TDihI=; b=gVOiCJ3nBNC6dt/+Nwp7wCBeGF+cfUHGxv4LDwGRopix/e3njKl13lZMZV9mVT4xNg 2fTG004JKbg9Qlu9w6lG3eBQwwcemdH8t9aDJQdyCQSVcaV65i9sEcTobpjNVuFEFFz6 p4nTNkiIGZhaHIAem3EaY7SJTIYn/+iYsPr7l+JGpMbgcZ0XV+Ak7mHJDeXF7VK46oCD jDGYhlwXdGXYSoJ+jnjKH0O7bN2rp2zNTaM69Sn+kTSoTL0fD1gar5cVmpXAA1BKg3Gz M2AxURO94CYXR1q9fJKuWNCR1lFkE+mnNGdLPNQtNd3yfVyWqAvdfbYRkxaZSiH2GWFJ tT1Q== X-Gm-Message-State: AOAM530k/maHDAxtBN/H3W4bWdus5XjZHbW8bihKnIxEFLha8DsjhNT4 HDRRfjYDKz2+FCz9mzFyrs+evg== X-Google-Smtp-Source: ABdhPJyVaUMi3QM5fgunw34SWHPdUjFvccvZwpUY2X24xSPN+9uw382QeTI2RaCTvwGaXQYr6tJHZg== X-Received: by 2002:a62:75d0:0:b029:1b8:ae4d:620c with SMTP id q199-20020a6275d00000b02901b8ae4d620cmr5646338pfc.80.1611084904912; Tue, 19 Jan 2021 11:35:04 -0800 (PST) Received: from google.com ([2620:15c:f:10:1ea0:b8ff:fe73:50f5]) by smtp.gmail.com with ESMTPSA id u68sm19484064pfu.195.2021.01.19.11.35.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Jan 2021 11:35:04 -0800 (PST) Date: Tue, 19 Jan 2021 11:34:57 -0800 From: Sean Christopherson To: Andy Lutomirski Cc: x86@kernel.org, LKML , Krzysztof Mazur , Krzysztof =?utf-8?Q?Ol=C4=99dzki?= , Arnd Bergmann Subject: Re: [PATCH v2 1/4] x86/fpu: Add kernel_fpu_begin_mask() to selectively initialize state Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 19, 2021, Andy Lutomirski wrote: > diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c > index eb86a2b831b1..d4a71596c41e 100644 > --- a/arch/x86/kernel/fpu/core.c > +++ b/arch/x86/kernel/fpu/core.c > @@ -121,7 +121,7 @@ int copy_fpregs_to_fpstate(struct fpu *fpu) > } > EXPORT_SYMBOL(copy_fpregs_to_fpstate); > > -void kernel_fpu_begin(void) > +void kernel_fpu_begin_mask(unsigned int kfpu_mask) > { > preempt_disable(); > > @@ -141,13 +141,18 @@ void kernel_fpu_begin(void) > } > __cpu_invalidate_fpregs_state(); > > - if (boot_cpu_has(X86_FEATURE_XMM)) > - ldmxcsr(MXCSR_DEFAULT); > + /* Put sane initial values into the control registers. */ > + if (likely(kfpu_mask & KFPU_MXCSR)) { > + if (boot_cpu_has(X86_FEATURE_XMM)) > + ldmxcsr(MXCSR_DEFAULT); > + } > > - if (boot_cpu_has(X86_FEATURE_FPU)) > - asm volatile ("fninit"); > + if (unlikely(kfpu_mask & KFPU_387)) { > + if (boot_cpu_has(X86_FEATURE_FPU)) > + asm volatile ("fninit"); > + } Why not combine these into a single if statement? Easier on the eyes (IMO), and would generate a smaller diff. if (likely(kfpu_mask & KFPU_MXCSR) && boot_cpu_has(X86_FEATURE_XMM)) ldmxcsr(MXCSR_DEFAULT); if (unlikely(kfpu_mask & KFPU_387) && boot_cpu_has(X86_FEATURE_FPU)) asm volatile ("fninit"); > } > -EXPORT_SYMBOL_GPL(kernel_fpu_begin); > +EXPORT_SYMBOL_GPL(kernel_fpu_begin_mask); > > void kernel_fpu_end(void) > { > -- > 2.29.2 >