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 CEBE1C4332F for ; Mon, 6 Nov 2023 09:19:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231295AbjKFJTi (ORCPT ); Mon, 6 Nov 2023 04:19:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231246AbjKFJTh (ORCPT ); Mon, 6 Nov 2023 04:19:37 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1372DDF for ; Mon, 6 Nov 2023 01:19:35 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5097FC433C7; Mon, 6 Nov 2023 09:19:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1699262374; bh=aHhtLAr9nrJf9m45UpSxg2nODXqnnAIz/Ob1w49xLxA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=yLdTx6sgvn//UnmlBRM5rtVywfF0pg9YirXq+zMSOa91z//OGhRZB6VC8RybwCEXE ZExs/l9D74E5EbDkaWrwLEnxPBzbiDdJ5zEJRPfJKkxLwFXG5mYMTwrnlmCs0hF1nS hlz+1I/Y1FqYDLJvURroxts/Inhk8Q4rR2AK+Kg8= Date: Mon, 6 Nov 2023 10:19:32 +0100 From: Greg KH To: Mahmoud Adam Cc: stable@vger.kernel.org Subject: Re: backport "x86: change default to spec_store_bypass_disable=prctl spectre_v2_user=prctl" Message-ID: <2023110617-had-drier-c367@gregkh> References: <2023101401-boxer-grandpa-6e31@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Wed, Nov 01, 2023 at 04:15:24PM +0100, Mahmoud Adam wrote: > > Why is this required at all? It just changes a default option, you can > > set the "faster" option yourself if you really feel it is a good idea > > for older kernels, why can't you do that for containers you want it > > enabled on for these older kernels? > > The patch has already motivations of why this is a better default, and > changing this would give performance improvements > > > And what exact kernel versions did you test this on? > > this was tested on 5.15 and 5.10 > > > And how is this not a new feature? > > As you mentioned it changes the default option, Why is this considered a > new feature? Changing the default option when booting is a new feature in that it changes what was previously happening before. And, anyone running those old kernels, if they are comfortable with making this feature the default, in order to get the performance increase you say is there, can change their command line to do so, no kernel changes needed. So for now, I'll leave this as-is, thanks. greg k-h