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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 15F87C4345F for ; Fri, 19 Apr 2024 14:04:17 +0000 (UTC) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=WJrriT5J; dkim-atps=neutral Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4VLbwv4g7bz3dJd for ; Sat, 20 Apr 2024 00:04:15 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=WJrriT5J; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=2604:1380:4641:c500::1; helo=dfw.source.kernel.org; envelope-from=will@kernel.org; receiver=lists.ozlabs.org) Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4VLbw33N1Rz2xmC for ; Sat, 20 Apr 2024 00:03:31 +1000 (AEST) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 9DCB0619D7; Fri, 19 Apr 2024 14:03:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 72650C072AA; Fri, 19 Apr 2024 14:03:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713535409; bh=DU2Oh8nrRgXZi/yPndOQwhsltv4XMpBfwRnb1FWmP0Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=WJrriT5J2X7hf4oYYUmstmlkPeq3DgvatCicCKVfFY05MHAXsGjIvsIH6c2UeFUCK b1tQA9eFfPT9My24Bx5MwU3csOfL2xbVgwabrXecyWtYmZRKLwmjFTjcB9j5GYWGoy bTMMwme5TOdiXtbdlz/weS3ViPl7AR23/VsdRSztQE4oWHicuv1Q1F6jzoDfRx6oFs e91S/8iEAE+36zTfeMrMhg/6jsGIwDPTUf6JEt6bvmNpYbnQaXgYkrjgO5C+kCE1Jv URoPOjT0e9X5jEpWoycpzzCiinEHMpKHGeCeKhjSjfGUKHI96+oFtwuokS//ELD+RL Qpa7Bkn0p5REw== Date: Fri, 19 Apr 2024 15:03:22 +0100 From: Will Deacon To: Sean Christopherson Subject: Re: [PATCH 1/3] x86/cpu: Actually turn off mitigations by default for SPECULATION_MITIGATIONS=n Message-ID: <20240419140321.GF3148@willie-the-truck> References: <20240409175108.1512861-1-seanjc@google.com> <20240409175108.1512861-2-seanjc@google.com> <20240413115324.53303a68@canb.auug.org.au> <87edb9d33r.fsf@mail.lhotse> <87bk6dd2l4.fsf@mail.lhotse> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Stephen Rothwell , x86@kernel.org, Jonathan Corbet , Peter Zijlstra , Pawan Gupta , Dave Hansen , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Linux-Renesas , Heiko Carstens , Ingo Molnar , Geert Uytterhoeven , Catalin Marinas , Borislav Petkov , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, Josh Poimboeuf , Daniel Sneddon Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Mon, Apr 15, 2024 at 07:31:23AM -0700, Sean Christopherson wrote: > On Mon, Apr 15, 2024, Geert Uytterhoeven wrote: > > On Sat, Apr 13, 2024 at 11:38 AM Michael Ellerman wrote: > > > Michael Ellerman writes: > > > > Stephen Rothwell writes: > > > ... > > > >> On Tue, 9 Apr 2024 10:51:05 -0700 Sean Christopherson wrote: > > > ... > > > >>> diff --git a/kernel/cpu.c b/kernel/cpu.c > > > >>> index 8f6affd051f7..07ad53b7f119 100644 > > > >>> --- a/kernel/cpu.c > > > >>> +++ b/kernel/cpu.c > > > >>> @@ -3207,7 +3207,8 @@ enum cpu_mitigations { > > > >>> }; > > > >>> > > > >>> static enum cpu_mitigations cpu_mitigations __ro_after_init = > > > >>> - CPU_MITIGATIONS_AUTO; > > > >>> + IS_ENABLED(CONFIG_SPECULATION_MITIGATIONS) ? CPU_MITIGATIONS_AUTO : > > > >>> + CPU_MITIGATIONS_OFF; > > > >>> > > > >>> static int __init mitigations_parse_cmdline(char *arg) > > > >>> { > > > > > > I think a minimal workaround/fix would be: > > > > > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig > > > index 2b8fd6bb7da0..290be2f9e909 100644 > > > --- a/drivers/base/Kconfig > > > +++ b/drivers/base/Kconfig > > > @@ -191,6 +191,10 @@ config GENERIC_CPU_AUTOPROBE > > > config GENERIC_CPU_VULNERABILITIES > > > bool > > > > > > +config SPECULATION_MITIGATIONS > > > + def_bool y > > > + depends on !X86 > > > + > > > config SOC_BUS > > > bool > > > select GLOB > > > > Thanks, that works for me (on arm64), so > > Tested-by: Geert Uytterhoeven > > Oof. I completely missed that "cpu_mitigations" wasn't x86-only. I can't think > of better solution than an on-by-default generic Kconfig, though can't that it > more simply be: > > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig > index 2b8fd6bb7da0..5930cb56ee29 100644 > --- a/drivers/base/Kconfig > +++ b/drivers/base/Kconfig > @@ -191,6 +191,9 @@ config GENERIC_CPU_AUTOPROBE > config GENERIC_CPU_VULNERABILITIES > bool > > +config SPECULATION_MITIGATIONS > + def_bool !X86 > + > config SOC_BUS > bool > select GLOB I can't see this in -next yet. Do you plan to post it as a proper patch to collect acks etc? Cheers, Will