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 925FBC433EF for ; Sat, 23 Jul 2022 21:51:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235578AbiGWVvW (ORCPT ); Sat, 23 Jul 2022 17:51:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48744 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231720AbiGWVvS (ORCPT ); Sat, 23 Jul 2022 17:51:18 -0400 Received: from tartarus.angband.pl (tartarus.angband.pl [51.83.246.204]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1BA0F1AD81 for ; Sat, 23 Jul 2022 14:51:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=angband.pl; s=tartarus; h=In-Reply-To:Content-Transfer-Encoding:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=E8m+xLzbfrZi9Nc2uLK+1RiRF1Jn5Hva1blr5jB++Cw=; b=JkARt4H82iYVI7DaV7IKx3NN4q uArbfoeLPWyjufVFVNYF+zQzsqYB9kQ8chFAw3RbkLVij6wh9AJOIlGSZZGNsYlKzOw0ysGX0WhKP dRXNDWoXd+ESyvuZ3+Y1P1Smf8RFSBOkHHN3fCV8VgbxxjqiSu1IvVm2EN1Lrona/FKo=; Received: from kilobyte by tartarus.angband.pl with local (Exim 4.94.2) (envelope-from ) id 1oFN1I-004Nuk-5B; Sat, 23 Jul 2022 23:50:44 +0200 Date: Sat, 23 Jul 2022 23:50:44 +0200 From: Adam Borowski To: Greg Kroah-Hartman Cc: Naresh Kamboju , open list , X86 ML , lkft-triage@lists.linaro.org, Borislav Petkov , Pawan Gupta , Peter Zijlstra , Josh Poimboeuf Subject: Re: RETBleed: WARNING: Spectre v2 mitigation leaves CPU vulnerable to RETBleed attacks, data leaks possible! Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Junkbait: aaron@angband.pl, zzyx@angband.pl X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: kilobyte@angband.pl X-SA-Exim-Scanned: No (on tartarus.angband.pl); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 14, 2022 at 11:01:12AM +0200, Greg Kroah-Hartman wrote: > On Thu, Jul 14, 2022 at 02:15:07PM +0530, Naresh Kamboju wrote: > > We are booting the i386 kernel on an x86 machine. > > With Spectre V2 patches merged into Linux mainline we have been noticing > > RETBleed: WARNING: Spectre v2 mitigation leaves CPU vulnerable to > > RETBleed attacks, data leaks possible! > > That's funny. I don't think that's a valid combination that should be > cared about, but I'll leave it to Pawan to comment if it is something > that is "real" to be concerned for. Alas, some people still run that because of not knowing any better. Until not so long ago, they were proposed with two install media, "32-bit" and "64-bit", but no explanation. Upgrades keep working, crossgrades are still only for the brave of the heart, and reinstalling might not appear to have a reason compelling enough. And for quite some tasks, halved word size (thus ~2/3 memory usage) can overcome register starvation and win benchmarks. Thus I wonder: perhaps such combinations we consider to be invalid should refuse to boot unless given a cmdline parameter? Meow! -- ⢀⣴⠾⠻⢶⣦⠀ ⣾⠁⢠⠒⠀⣿⡁ What kind of a drug are "base" and "red pill"? I think acid is ⢿⡄⠘⠷⠚⠋⠀ LSD, which would make base... ? Judging from the behaviour of ⠈⠳⣄⠀⠀⠀⠀ those "based and redpilled", something nasty.