From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Wang2 Subject: Re: IOMMU support for xen in BIOS of AMD based HP DL385g7 and kernel 3.0.0-rc7 Date: Tue, 26 Jul 2011 13:47:34 +0200 Message-ID: <201107261347.35313.wei.wang2@amd.com> References: <4E22BAB9.5050002@it-infrastrukturen.com> <4E284B8E.7000102@it-infrastrukturen.com> <20110725090335.GG21948@amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20110725090335.GG21948@amd.com> Content-Disposition: inline List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "Roedel, Joerg" Cc: "M. Schneider" , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Monday 25 July 2011 11:03:35 Roedel, Joerg wrote: > 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: > > >> Please allow me one question about IOMMU support in AMDS's 890FX > > >> chipset and 6176SE CPUs used in HP DL385g7 servers. These chips > > >> support IOMMU as far as I know. BIOS of HP DL385g7 doesn't currently > > >> offer an IOMMU flag. > > >> > > >> I have contacted already HP support due to this missing BIOS setting > > >> options but less or more my request has been ignored (no solution and > > >> no plans for solving of this important issue yet) so I am looking f= or > > >> a workaround as IOMMU support is required for passing thoruhg of PCI > > >> devices to domU domains (xen 4.0 / 4.1). > > > > > > 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. > > > > Thank you very much fo your answer J=F6rg. > > > > Some BIOSes (like BIOS of HD DL385g7 server with AMD CPUs) don't have > > the IOMMU option. > > I have to correct my prevoius email as HP DL385g7 servers have the AMD > > SR5690/SP5100 chipset (supporting IOMMU). > > > > Is it possible to write a workaround for xen 4.1 or 4.2 to create such > > IVRS table in code (in case it has static entries for specific server > > type) and add a boot option like "iommu=3Dforce-dl385g7" ? > > > > 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. Xen also relies on BIOS to setup IVRS table for iommu device. You could als= o=20 look at Xen 3.2, there were some old bits that enables iommu directly using= =20 pci configure space. But just as Joerg said, this was not an optimal and=20 reliable way to enable iommu, we do not maintain these codes any more. Thanks, Wei > Regards, > > Joerg