From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joanna Rutkowska Subject: Re: feature suggestion: DMAR table emulation for Xen Date: Fri, 14 May 2010 11:22:58 +0200 Message-ID: <4BED1672.6000903@invisiblethingslab.com> References: <4BEC0928.8090604@invisiblethingslab.com> <987664A83D2D224EAE907B061CE93D53C60548F1@orsmsx505.amr.corp.intel.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1822458740==" Return-path: In-Reply-To: <987664A83D2D224EAE907B061CE93D53C60548F1@orsmsx505.amr.corp.intel.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: "Kay, Allen M" Cc: "Cihula, Joseph" , "xen-devel@lists.xensource.com" , "Han, Weidong" List-Id: xen-devel@lists.xenproject.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --===============1822458740== Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig1B571373431DD35AF7D29862" This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig1B571373431DD35AF7D29862 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 05/14/2010 07:41 AM, Kay, Allen M wrote: > Joanna, >=20 > RMRR memory ranges specified memory ranges that might be used for > BIOS initiated DMA's for USB and integrated graphics devices. These > ranges are set by the BIOS. >=20 > Do they stay the same across different platforms? >=20 To be frank, those RMRR ranges have always been a bit of a mystery for me. Do you actually know any OS drivers for USB devices that would depend on them? Aren't they only used by the BIOS to implement various dirty tricks they like to implement? The Intel VT-d spec says that: "USB controllers and UMA integrated graphics devices are the only legacy device usages identified that depend on DMA to reserved system memory". I think we can safely ignore the legacy integrated graphics devices, because I would expect any VT-d enabled platform to have a modern graphics device and modern OS drivers that works well with VT-d (you even provide a dedicated DMA Remapping Unit for your integrated graphics device, so I would expect it doesn't require any RMMR exceptions). So USB devices seem to be the only potential problem. But USB devices are implemented by the ICH, which in most cases is Intel ICH9, or 10. So, if we took a DMAR from a platform, say PM45+ICH9M w/ Intel BIOS, it should also work fine on any other laptop with this chipset (and probably other variants too), just minus the potential BIOS-specific-dirty-tricks...? joanna. --------------enig1B571373431DD35AF7D29862 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iEYEARECAAYFAkvtFncACgkQORdkotfEW86imwCfeEQ8RSNlFWfcEgWz3AX2PpW+ QOoAoMv4Zh0pQQoiPBgp5w11C7Jvf2gS =cKhh -----END PGP SIGNATURE----- --------------enig1B571373431DD35AF7D29862-- --===============1822458740== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel --===============1822458740==--