Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750867AbWC0KTO (ORCPT ); Mon, 27 Mar 2006 05:19:14 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750872AbWC0KTO (ORCPT ); Mon, 27 Mar 2006 05:19:14 -0500 Received: from mail05.syd.optusnet.com.au ([211.29.132.186]:54498 "EHLO mail05.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S1750864AbWC0KTN (ORCPT ); Mon, 27 Mar 2006 05:19:13 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <17447.47871.35204.347588@wombat.chubb.wattle.id.au> Date: Mon, 27 Mar 2006 21:14:23 +1100 From: Peter Chubb To: Jeff Garzik Cc: Ian Pratt , Anthony Liguori , Chris Wright , virtualization@lists.osdl.org, xen-devel@lists.xensource.com, linux-kernel@vger.kernel.org, Ian Pratt , ian.pratt@cl.cam.ac.uk, SCSI Mailing List Subject: Re: [RFC PATCH 35/35] Add Xen virtual block device driver. In-Reply-To: <4421D943.1090804@garzik.org> References: <4421D943.1090804@garzik.org> X-Mailer: VM 7.17 under 21.4 (patch 17) "Jumbo Shrimp" XEmacs Lucid Comments: Hyperbole mail buttons accepted, v04.18. X-Face: GgFg(Z>fx((4\32hvXq<)|jndSniCH~~$D)Ka:P@e@JR1P%Vr}EwUdfwf-4j\rUs#JR{'h# !]])6%Jh~b$VA|ALhnpPiHu[-x~@<"@Iv&|%R)Fq[[,(&Z'O)Q)xCqe1\M[F8#9l8~}#u$S$Rm`S9% \'T@`:&8>Sb*c5d'=eDYI&GF`+t[LfDH="MP5rwOO]w>ALi7'=QJHz&y&C&TE_3j! Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2154 Lines: 43 >>>>> "Jeff" == Jeff Garzik writes: Jeff> Ian Pratt wrote: >> >> We certainly should be pushing everyone toward using the 'xdX' etc >> devices that are allocated to us. However, the installers of >> certain older distros and other user space tools won't except >> anything other than hdX/sdX, so its useful from a compatibility POV >> even if it never goes into mainline, which I agree it probably >> shouldn't. Jeff> Yes, this is true. Red Hat installer guys grumbled at me when I Jeff> wrote the 'sx8' block driver: since it wasn't hda/sda, they had Jeff> to write special code for it, as they apparently must do for any Jeff> new block driver "class". SuSE and other distros are probably Jeff> similar, since each block driver provides its own special Jeff> behaviors and feature exports. Jeff> I should have spoken up a long time ago about this, but anyway: Jeff> An IBM hypervisor on ppc64 communicates uses SCSI RPC messages. Jeff> I think this would be quite nice for Xen, because SCSI (a) is a Jeff> message-based model, and (b) implementing block using SCSI has a Jeff> very high Just Works(tm) value which cannot be ignored. And Jeff> perhaps (c) SCSI target code already exists, so implementing the Jeff> server side doesn't require starting from scratch, but rather Jeff> simply connecting the Legos. The IA64 virtualisation work (Xen and Linux-on-Linux) uses the SKI simulator virtual scsi device --- which looks just like any other scsi disk, but uses hypervisor calls to do read/write/open/close calls like a user-mode process. For performance, it needs to be extended a bit to do asynchronous I/O and interrupt on completion. As a halfway house, the ski simscsi driver would be fairly easy to port, I think. -- Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au http://www.ertos.nicta.com.au ERTOS within National ICT Australia - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/