From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752126Ab1EKPfu (ORCPT ); Wed, 11 May 2011 11:35:50 -0400 Received: from mga14.intel.com ([143.182.124.37]:33235 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751775Ab1EKPfr (ORCPT ); Wed, 11 May 2011 11:35:47 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.64,353,1301900400"; d="p7s'?scan'208";a="434335041" From: "Woodhouse, David" To: "Song, Youquan" CC: "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "mingo@elte.hu" , "tglx@linutronix.de" , "hpa@zytor.com" , "hpa@linux.intel.com" , "Kay, Allen M" , "Siddha, Suresh B" , "Liu, Kent" , Youquan Song Date: Wed, 11 May 2011 16:07:10 +0100 Subject: Re: [PATCH v2] x86, vt-d: enable x2apic opt out Thread-Topic: [PATCH v2] x86, vt-d: enable x2apic opt out Thread-Index: AcwP7RteTSP5RDwVSRyloGZUfY867g== Message-ID: <1305126431.30435.163.camel@i7.infradead.org> References: <1302764783-24491-1-git-send-email-youquan.song@intel.com> In-Reply-To: <1302764783-24491-1-git-send-email-youquan.song@intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/signed; micalg=sha1; protocol="application/x-pkcs7-signature"; boundary="=-QPvqPtykwtt/cuWZUved" MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-QPvqPtykwtt/cuWZUved Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2011-04-14 at 08:06 +0100, Song, Youquan wrote: > New version of VT-d2 specification (http://download.intel.com/technology > /computing/vptech/Intel(r)_VT_for_Direct_IO.pdf) includes a new feature t= hat=20 > provide firmware a way to request system software to opt out of enable x2= APIC > mode. DMAR ACPI table newly define flags.1 bit: x2APIC_OPT_OUT which is s= et to > request System software opt out xAPIC mode if flags.0 bit:INTR_REMAP is a= lso > set. >=20 > This patch enable the feature. Also re-define x2apic_supported() to addre= ss > platform x2apic support needs 1)processor has x2apic capability 2)interru= pt > remapping support 3)firmware does not request opt-out.=20 Given that x2apic is *required* to be safe from irq injection tricks, why would we ever want to manually disable it? Is this just a workaround for a crappy BIOS? What is the *actual* reason for wanting to disable x2apic? --=20 David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation --=-QPvqPtykwtt/cuWZUved Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIVTDCCAz0w ggKmoAMCAQICAwWw/zANBgkqhkiG9w0BAQUFADBOMQswCQYDVQQGEwJVUzEQMA4GA1UEChMHRXF1 aWZheDEtMCsGA1UECxMkRXF1aWZheCBTZWN1cmUgQ2VydGlmaWNhdGUgQXV0aG9yaXR5MB4XDTA2 MDIxNjE4MDEzMFoXDTE2MDIxOTE4MDEzMFowUjELMAkGA1UEBhMCVVMxGjAYBgNVBAoTEUludGVs IENvcnBvcmF0aW9uMScwJQYDVQQDEx5JbnRlbCBFeHRlcm5hbCBCYXNpYyBQb2xpY3kgQ0EwggEi MA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDBpd/XOb9QVqEZ8mQ1042TdOIq3ATDIsV2xDyt 30yLyMR5Wjtus0bn3B+he89BiNO/LP6+rFzEwlD55PlX+HLGIKeNNG97dqyc30FElEUjZzTZFq2N 4e3kVJ/XAEEgANzV8v9qp7qWwxugPgfc3z9BkYot+CifozexHLb/hEZj+yISCU61kRZvuSQ0E11y 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