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 7F0F8C61DB3 for ; Thu, 12 Jan 2023 10:40:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236892AbjALKks (ORCPT ); Thu, 12 Jan 2023 05:40:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39692 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232433AbjALKjk (ORCPT ); Thu, 12 Jan 2023 05:39:40 -0500 Received: from mail.skyhub.de (mail.skyhub.de [IPv6:2a01:4f8:190:11c2::b:1457]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 305996586 for ; Thu, 12 Jan 2023 02:34:16 -0800 (PST) Received: from zn.tnic (p5de8e9fe.dip0.t-ipconnect.de [93.232.233.254]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 824171EC04A9; Thu, 12 Jan 2023 11:34:14 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1673519654; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=CJ1uL2ZqSBbV653T/Ui6KWFShGRfcaqwoq4TgOsz5Q0=; b=PciC4Qa5czY4g5t8Yzc7JIAhA6koQP0Ox6MVVEXSKlsBLa8JSZmEb/nmDHtJpIZSynNnfR TxGIJuX14Rz6hmdaXwSy9qWrKlCVjGbSsY9bWR0N18MdQddWRJtPvXclfvh7dPkz3Oa8JB D9qiK40XVjjAhDtmWAbkS7t9AvtbAk8= Date: Thu, 12 Jan 2023 11:34:08 +0100 From: Borislav Petkov To: Pawan Gupta Cc: Breno Leitao , tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, jpoimboe@kernel.org, peterz@infradead.org, x86@kernel.org, cascardo@canonical.com, leit@meta.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] x86/bugs: Explicitly clear speculative MSR bits Message-ID: References: <20221128153148.1129350-1-leitao@debian.org> <20230112070037.q6cg23tn57onmxfi@desk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20230112070037.q6cg23tn57onmxfi@desk> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 11, 2023 at 11:00:37PM -0800, Pawan Gupta wrote: > > SPEC_CTRL_RRSBA_DIS_S is a disable bit and I presume it needs to stay enabled. > > The mitigation is enabled when this bit is set. When set, it prevents RET > target to be predicted from alternate predictors (BTB). This should stay > 0, unless enabled by a mitigation mode. > > > Only when spec_ctrl_disable_kernel_rrsba() runs. And I'd say perf-wise it > > doesn't cost that much... > > I guess this doesn't matter now, because this patch is resetting it by > default that keeps the mitigation disabled with no perf impact. Ok, lemme queue it then. Thx. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette