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,URIBL_BLOCKED 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 49623C433E0 for ; Wed, 5 Aug 2020 05:12:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F474207FC for ; Wed, 5 Aug 2020 05:12:54 +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="FG2VCEsK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726158AbgHEFMw (ORCPT ); Wed, 5 Aug 2020 01:12:52 -0400 Received: from terminus.zytor.com ([198.137.202.136]:53135 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725372AbgHEFMw (ORCPT ); Wed, 5 Aug 2020 01:12:52 -0400 Received: from [IPv6:2601:646:8600:3281:4d47:1bf:1c0:ca78] ([IPv6:2601:646:8600:3281:4d47:1bf:1c0:ca78]) (authenticated bits=0) by mail.zytor.com (8.15.2/8.15.2) with ESMTPSA id 0755AV731344388 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Tue, 4 Aug 2020 22:10:31 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 0755AV731344388 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2020072401; t=1596604231; bh=9mqOS6RNAraQiHKEtxREY8I8rwz6Kyg/eHWTnjLyUwE=; h=Date:In-Reply-To:References:Subject:To:CC:From:From; b=FG2VCEsKz9kEVGxIgEwB1tK2lmtTvgeODXqDe9q3HM8LRX2bu5TGi6UoMSvXSorTu 5ZGXx3usLhVO/VlSx7mAP1wj3ttXL4MO358JAyc7iuyk375HFxqYlOkuF9h6w6LEbb HMzYCsCr+iqVRrtapBxil0xbkK7ItXV/W6krqNheu7zV94fooKhJT63wPuOUipO85C umTQ22XzKp9hyt0hMwJ9RTEJGr61r7hQtw/z1HpmwEt79oqptvUadw9uT4XMXJ0mRJ 8HL4DeMFmXf24o4UTjuVYVtcEh8JgocQ2Dx5oAjLDIk3JE0xVScDKO02yOQtSfiHtY q23EWnv9PVziA== Date: Tue, 04 Aug 2020 22:10:22 -0700 User-Agent: K-9 Mail for Android In-Reply-To: <20200805050808.GC9127@nazgul.tnic> References: <20200805021059.1331-1-ricardo.neri-calderon@linux.intel.com> <20200805044840.GA9127@nazgul.tnic> <47A60E6A-0742-45FB-B707-175E87C58184@zytor.com> <20200805050808.GC9127@nazgul.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [PATCH v2] x86/cpu: Use SERIALIZE in sync_core() when available To: Borislav Petkov CC: Borislav Petkov , Ricardo Neri , Thomas Gleixner , Ingo Molnar , Andy Lutomirski , x86@kernel.org, "Peter Zijlstra (Intel)" , 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: <2511352F-5D28-4337-A4A2-1B54073F1F72@zytor.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On August 4, 2020 10:08:08 PM PDT, Borislav Petkov wrote: >On Tue, Aug 04, 2020 at 09:58:25PM -0700, hpa@zytor=2Ecom wrote: >> Because why use an alternative to jump over one instruction? >> >> I personally would prefer to have the IRET put out of line > >Can't yet - SERIALIZE CPUs are a minority at the moment=2E > >> and have the call/jmp replaced by SERIALIZE inline=2E > >Well, we could do: > > alternative_io("=2E=2E=2E IRET bunch", __ASM_SERIALIZE, >X86_FEATURE_SERIALIZE, =2E=2E=2E); > >and avoid all kinds of jumping=2E Alternatives get padded so there >would be a couple of NOPs following when SERIALIZE gets patched in >but it shouldn't be a problem=2E I guess one needs to look at what gcc >generates=2E=2E=2E I didn't say behind a trap=2E IRET is a control transfer instruction, and = slow, so putting it out of line really isn't unreasonable=2E Can even do a = call to a common handler=2E --=20 Sent from my Android device with K-9 Mail=2E Please excuse my brevity=2E