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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0F9C1ECDE30 for ; Wed, 17 Oct 2018 10:56:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 77BF3214D5 for ; Wed, 17 Oct 2018 10:56:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 77BF3214D5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ucw.cz Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727040AbeJQSvV (ORCPT ); Wed, 17 Oct 2018 14:51:21 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:58013 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726861AbeJQSvV (ORCPT ); Wed, 17 Oct 2018 14:51:21 -0400 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 512) id 2D1FF80771; Wed, 17 Oct 2018 12:56:10 +0200 (CEST) Date: Wed, 17 Oct 2018 12:56:10 +0200 From: Pavel Machek To: vbabka@suse.cz, mhocko@suse.com, hpa@zytor.com, torvalds@linux-foundation.org, ak@linux.intel.com, dave.hansen@intel.com, kernel list , tglx@linutronix.de, mingo@redhat.com, bp@alien8.de Subject: l1tf: Kernel suggests I throw away third of my memory. I'd rather not Message-ID: <20181017105610.GA4260@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="9jxsPFA5p3P2qPhR" Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --9jxsPFA5p3P2qPhR Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! 6a012288 suggests I throw away 1GB on RAM. On 3GB system.. that is not going to be pleasant. l1tf.html says: # The Linux kernel contains a mitigation for this attack vector, PTE # inversion, which is permanently enabled and has no performance # impact. I don't believe it has "no" performance impact, but I guess it is lost in the noise. # The kernel ensures that the address bits of PTEs, which are # not marked present, never point to cacheable physical memory space. # A system with an up to date kernel is protected against attacks from # malicious user space applications. These are not true. cat /sys/devices/system/cpu/vulnerabilities/l1tf Vulnerable uname -a Linux amd 4.19.0-rc8-next-20181017autobisect1539371050 #189 SMP Wed Oct 17 12:04:23 CEST 2018 i686 GNU/Linux Now question is... can we do better? Kernel stores information about swapped-out pages there, right? That sounds like a cool hack, but maybe it is time to get rid of that hack? As a workaround, can I simply do swapoff -a to be safe for now? Thanks, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --9jxsPFA5p3P2qPhR Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAlvHFUoACgkQMOfwapXb+vKKGACaAguJ7YrkEaCpN6n0RH1qizCU RrQAn0Zu7+U52FifW4jgGhsYxPCRaWfV =IN6k -----END PGP SIGNATURE----- --9jxsPFA5p3P2qPhR--