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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5D7E7ECAAA1 for ; Tue, 30 Aug 2022 13:35:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230033AbiH3Nfh (ORCPT ); Tue, 30 Aug 2022 09:35:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229870AbiH3Nfc (ORCPT ); Tue, 30 Aug 2022 09:35:32 -0400 Received: from mail-wr1-x432.google.com (mail-wr1-x432.google.com [IPv6:2a00:1450:4864:20::432]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EB95D4B0C1; Tue, 30 Aug 2022 06:35:30 -0700 (PDT) Received: by mail-wr1-x432.google.com with SMTP id c7so7594069wrp.11; Tue, 30 Aug 2022 06:35:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc; bh=JpguWKHCz7w89q6BLLDu3VHzbooJ+x9K5EqEg9fOx8M=; b=c2pG9ATJI7Vfg1cNbQDHpSFAphTLeHsKffxD2fhvclwhvmDc8MNye2JlUVbiFLEwyI an267YrcHIQxDvJJq3UfNMKVtHmyVegrYXiT4eFRoLbf/ApQADUClSgf4SzlghwDphB9 51BBe9PZr82GWYUQesDCcL1ol9dmIXPPk5QuqUPcvBNRfEGjiKk61hLof6VNvEefWiIx qth/JeKZSuuSYcwR+WN474a/hSBvgy1rEXHXQ2rREECA7TUQtAmg8P+ewovvPqo+XA3P 2IFOLOKpg2HDOEYA55JiuKtODLt/IPk6TT02zC/Pp9HEpi0LrMYw4DJrNU0qvfCH3eMI LAcw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc; bh=JpguWKHCz7w89q6BLLDu3VHzbooJ+x9K5EqEg9fOx8M=; b=En/AB4WfGo3pxQzTf9JEOzDOH5l3+wpIOaRZNUtwt57YPdK6zeYNU5Wx5g7CLoTqTx Zs+/mzRzYSJIspXp+qsX4uONawrE7eiamRZcoAaEa9Axqk4LSDadu0y0MBabgC7E4UBF HwNovwMAAFoYxkN3zUvDae75LlvUTBkVlRDbXtRItJZFR63z/it3ao41RgVIajkJIfNv ZbkpoIlMMlrTValGZRmrgsYfPRB/tUxbrXJSgmuJA+kQXnmBM9PO3JrLS3ytSTUUsKix q6kuOoXrN/E1yeDtqeZylt3FT+bORUhACXT0QE+whv0crxcwExUXx3yL138i9G5QojcG Fz9w== X-Gm-Message-State: ACgBeo1XA5fBYB4TflJ51Xj6hqMfyfxTinztMyAtQzZqy3PtQBlsfXtG WYMG4br2zOXss2hNwBG9ai4= X-Google-Smtp-Source: AA6agR51Z+ds6I0M8yufiA5kSmLZU2RKP47ZMnLS09yHSfjWtCL9aMVHuotM8jobWxV0h43gw/6yEQ== X-Received: by 2002:a5d:51d2:0:b0:226:cfa4:a998 with SMTP id n18-20020a5d51d2000000b00226cfa4a998mr8880175wrv.689.1661866529306; Tue, 30 Aug 2022 06:35:29 -0700 (PDT) Received: from elende (elende.valinor.li. [2a01:4f9:6a:1c47::2]) by smtp.gmail.com with ESMTPSA id n5-20020a05600c3b8500b003a319b67f64sm3752650wms.0.2022.08.30.06.35.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Aug 2022 06:35:28 -0700 (PDT) Sender: Salvatore Bonaccorso Date: Tue, 30 Aug 2022 15:35:27 +0200 From: Salvatore Bonaccorso To: martin-eric.racine@iki.fi, 1017425@bugs.debian.org Cc: Peter Zijlstra , Ben Hutchings , x86@kernel.org, Linux Kernel Mailing List , stable@vger.kernel.org, regressions@lists.linux.dev, Daniel Sneddon , Pawan Gupta Subject: Re: Bug#1017425: [PATCH] x86/speculation: Avoid LFENCE in FILL_RETURN_BUFFER on CPUs that lack it Message-ID: References: <9395338630e3313c1bf0393ae507925d1f9af870.camel@decadent.org.uk> <166062224255.2056.9595118849979455037.reportbug@pxeth.lan> 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 Hi Martin, On Tue, Aug 30, 2022 at 03:18:51PM +0300, Martin-??ric Racine wrote: > On Tue, Aug 30, 2022 at 3:00 PM Peter Zijlstra wrote: > > On Tue, Aug 30, 2022 at 02:42:04PM +0300, Martin-??ric Racine wrote: > > > On Fri, Aug 19, 2022 at 3:15 PM Peter Zijlstra wrote: > > > > > > > > On Fri, Aug 19, 2022 at 01:38:27PM +0200, Ben Hutchings wrote: > > > > > > > > > So that puts the whole __FILL_RETURN_BUFFER inside an alternative, and > > > > > we can't have nested alternatives. That's unfortunate. > > > > > > > > Well, both alternatives end with the LFENCE instruction, so I could pull > > > > it out and do two consequtive ALTs, but unrolling the loop for i386 is > > > > a better solution in that the sequence, while larger, removes the need > > > > for the LFENCE. > > > > > > Have we reached a definitive conclusion on to how to fix this? > > > > https://git.kernel.org/tip/332924973725e8cdcc783c175f68cf7e162cb9e5 > > Thanks. > > Ben: When can we expect an updated kernel to security-updates at Debian? When the update is ready to go. Likely the update for the next point release for bullseye will contain the fix for this issue. Regards, Salvatore