From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Roedel, Joerg" Subject: Re: IOMMU support for xen in BIOS of AMD based HP DL385g7 and kernel 3.0.0-rc7 Date: Mon, 25 Jul 2011 11:03:35 +0200 Message-ID: <20110725090335.GG21948@amd.com> References: <4E22BAB9.5050002@it-infrastrukturen.com> <20110720124548.GA21948@amd.com> <4E284B8E.7000102@it-infrastrukturen.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: <4E284B8E.7000102@it-infrastrukturen.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "M. Schneider" Cc: wei.wang2@amd.com, "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Thu, Jul 21, 2011 at 11:53:50AM -0400, M. Schneider wrote: > Am 20.07.2011 14:45, schrieb Roedel, Joerg: > > On Sun, Jul 17, 2011 at 06:34:33AM -0400, M. Schneider wrote: > > =20 > >> Please allow me one question about IOMMU support in AMDS's 890FX chi= pset > >> and 6176SE CPUs used in HP DL385g7 servers. These chips support IOMM= U as > >> far as I know. BIOS of HP DL385g7 doesn't currently offer an IOMMU f= lag. > >> > >> I have contacted already HP support due to this missing BIOS setting > >> options but less or more my request has been ignored (no solution an= d no > >> plans for solving of this important issue yet) so I am looking for = a > >> workaround as IOMMU support is required for passing thoruhg of PCI > >> devices to domU domains (xen 4.0 / 4.1). > >> =20 > > I am sorry but if there is no IVRS table there is not much we can do. > > The IVRS table contains the information which device uses which > > request-ids. Without this information the IOMMU can not work reliably= . > > =20 >=20 > Thank you very much fo your answer J=F6rg. >=20 > Some BIOSes (like BIOS of HD DL385g7 server with AMD CPUs) don't have=20 > the IOMMU option. > I have to correct my prevoius email as HP DL385g7 servers have the AMD=20 > SR5690/SP5100 chipset (supporting IOMMU). >=20 > Is it possible to write a workaround for xen 4.1 or 4.2 to create such=20 > IVRS table in code (in case it has static entries for specific server=20 > type) and add a boot option like "iommu=3Dforce-dl385g7" ? >=20 > Thank you in advance for any hints. This is basically possible. The Xen code needs to do what the BIOS fails to do. But for Xen this is a lot more difficult to get right because Xen can not make the same assumptions about the hardware like a BIOS can. I can easily imagine that this will end in a maintenance nighmare if people start using this. I personally wouldn't do that for Linux, but it is up to the Xen IOMMU maintainer to decide that for the Xen side. I put Wei Wang on Cc, he maintains AMD IOMMU for Xen.=09 Regards, Joerg --=20 AMD Operating System Research Center Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach General Managers: Alberto Bozzo, Andrew Bowd Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 4= 3632