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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no 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 9BDB2C433E4 for ; Mon, 27 Jul 2020 12:49:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BE5C20714 for ; Mon, 27 Jul 2020 12:49:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="DHZId3Pf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728553AbgG0Mto (ORCPT ); Mon, 27 Jul 2020 08:49:44 -0400 Received: from terminus.zytor.com ([198.137.202.136]:44583 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728128AbgG0Mtn (ORCPT ); Mon, 27 Jul 2020 08:49:43 -0400 Received: from [IPv6:2601:646:8600:3281:d01e:b6c6:1a24:9007] ([IPv6:2601:646:8600:3281:d01e:b6c6:1a24:9007]) (authenticated bits=0) by mail.zytor.com (8.15.2/8.15.2) with ESMTPSA id 06RCnamc2000926 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Mon, 27 Jul 2020 05:49:36 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 06RCnamc2000926 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2020072401; t=1595854177; bh=vqJmEWTLIAFzkX9WqOPjctwd6uSnDgeS6aq26YK3uHw=; h=Date:In-Reply-To:References:Subject:To:CC:From:From; b=DHZId3PfHW7adFBQlkx07EAPJj0i99u0/lZgeMGbEOQOLOY2y3eUG24zclNKQ49N6 U6Q9We1ne+4bqiyKC2QCK4Cd9dOiiJJCaOYK6vZYns/h494qbqiN/VPuk/4dkGRMUe riQwxOMPJR4A9Ch/aQTRIvQ3IpZwdNLjp3+7X+tUF8Ehve92rkIxiorzOTnaArikqw MpDE0clQIJMsU9nZXXCJyGr6VeEzkG86jubXjeOpNgov1KxfyMah/qcGOn50CNUA7S J/Aq0iiNVowx68QPx+9eqQIpBH4/VbHKyeMaQFs/Kq8YTYpwFvaGlXvrI07p49GWt6 bLYufSNj/qGnQ== Date: Mon, 27 Jul 2020 05:49:28 -0700 User-Agent: K-9 Mail for Android In-Reply-To: <20200727083619.GF119549@hirez.programming.kicks-ass.net> References: <20200727043132.15082-1-ricardo.neri-calderon@linux.intel.com> <20200727043132.15082-5-ricardo.neri-calderon@linux.intel.com> <20200727083619.GF119549@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH 4/4] x86/cpu: Use SERIALIZE in sync_core() when available To: peterz@infradead.org CC: Ricardo Neri , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , x86@kernel.org, Dave Hansen , Tony Luck , Cathy Zhang , Fenghua Yu , Kyung Min Park , "Ravi V. Shankar" , Sean Christopherson , linux-kernel@vger.kernel.org, Ricardo Neri , Dave Hansen , linux-edac@vger.kernel.org From: hpa@zytor.com Message-ID: <49251CFA-8AC3-462D-A60F-0337593BE9CD@zytor.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On July 27, 2020 1:36:19 AM PDT, peterz@infradead=2Eorg wrote: >On Sun, Jul 26, 2020 at 10:55:15PM -0700, hpa@zytor=2Ecom wrote: >> For a really overenginered solution, but which might perform >> unnecessary poorly on existing hardware: >>=20 >> asm volatile("1: =2Ebyte 0xf, 0x1, 0xe8; 2:" >> _ASM_EXTABLE(1b,2b)); > >Ha! cute, you take an #UD ? > >We could optimize the #UD exception handler for this I suppose, but >that >makes it an even worse hack=2E The simple alternative() seems like a much >simpler approach=2E If this is in any way performance critical, then no :) Taking the #UD has = the cute property that we end up IRET on the way back, so we don't even nee= d a fix-up path=2E --=20 Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E