From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758139Ab1EXCTm (ORCPT ); Mon, 23 May 2011 22:19:42 -0400 Received: from lennier.cc.vt.edu ([198.82.162.213]:40733 "EHLO lennier.cc.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755737Ab1EXCTi (ORCPT ); Mon, 23 May 2011 22:19:38 -0400 X-Mailer: exmh version 2.7.2 01/07/2005 with nmh-1.3-dev To: Youquan Song Cc: linux-kernel@vger.kernel.org, david.woodhouse@intel.com, akpm@linux-foundation.org, mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com, hpa@linux.intel.com, allen.m.kay@intel.com, suresh.b.siddha@intel.com, rajesh.sankaran@intel.com, asit.k.mallick@intel.com, kent.liu@intel.com, Youquan Song Subject: Re: [PATCH v3] x86, vt-d: enable x2apic opt out In-Reply-To: Your message of "Mon, 23 May 2011 22:32:28 +0800." <1306161148-3987-1-git-send-email-youquan.song@intel.com> From: Valdis.Kletnieks@vt.edu References: <1306161148-3987-1-git-send-email-youquan.song@intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1306203521_3286P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Mon, 23 May 2011 22:18:41 -0400 Message-ID: <7457.1306203521@localhost> X-Mirapoint-Received-SPF: 198.82.161.152 auth3.smtp.vt.edu Valdis.Kletnieks@vt.edu 2 pass X-Mirapoint-IP-Reputation: reputation=neutral-1, source=Fixed, refid=n/a, actions=MAILHURDLE SPF TAG X-Junkmail-Status: score=10/50, host=vivi.cc.vt.edu X-Junkmail-Signature-Raw: score=unknown, refid=str=0001.0A020207.4DDB1586.009F,ss=1,fgs=0, ip=0.0.0.0, so=2010-07-22 22:03:31, dmn=2009-09-10 00:05:08, mode=single engine X-Junkmail-IWF: false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1306203521_3286P Content-Type: text/plain; charset=us-ascii On Mon, 23 May 2011 22:32:28 +0800, Youquan Song said: > + no_x2apic_optout [Default Off] > + With this option BIOS x2APIC opt-out request will be > + ignored. > + else if (!x2apic_supported() && cpu_has_x2apic) > + WARN(1, "Your BIOS is broken and requested that x2apic be " > + "disabled.\n This will leave your machine vulnerable to" > + " irq-injection attacks\n" > + "Use 'intel_iommu=no_x2apic_optout' to override BIOS " > + "request\n"); If we're doing a WARN level here, what are the downsides of just automagically forcing it rather than making them use a kernel parameter and reboot? Will some systems fail to boot because the BIOS was in fact right in requesting hat x2apic be turned off? --==_Exmh_1306203521_3286P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFN2xWBcC3lWbTT17ARAp+GAJ9FjFYCOmOlc7V9myPA6yGodqjGBgCgmlf/ yjvcLCqL/0Q46YlNAqxyHBg= =TURs -----END PGP SIGNATURE----- --==_Exmh_1306203521_3286P--