Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754808AbZIAQwP (ORCPT ); Tue, 1 Sep 2009 12:52:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753962AbZIAQwO (ORCPT ); Tue, 1 Sep 2009 12:52:14 -0400 Received: from cantor.suse.de ([195.135.220.2]:46377 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751687AbZIAQwN (ORCPT ); Tue, 1 Sep 2009 12:52:13 -0400 Subject: Re: [PATCH] SCSI driver for VMware's virtual HBA. From: James Bottomley To: Dmitry Torokhov Cc: Matthew Wilcox , Roland Dreier , Bart Van Assche , Alok Kataria , Robert Love , Randy Dunlap , Mike Christie , "linux-scsi@vger.kernel.org" , LKML , Andrew Morton , Rolf Eike Beer , Maxime Austruy In-Reply-To: <200909010933.50571.dtor@vmware.com> References: <1251415060.16297.58.camel@ank32.eng.vmware.com> <20090901161651.GO22870@parisc-linux.org> <200909010933.50571.dtor@vmware.com> Content-Type: text/plain Date: Tue, 01 Sep 2009 11:52:05 -0500 Message-Id: <1251823925.3864.216.camel@mulgrave.site> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2079 Lines: 40 On Tue, 2009-09-01 at 09:33 -0700, Dmitry Torokhov wrote: > On Tuesday 01 September 2009 09:16:51 am Matthew Wilcox wrote: > > On Tue, Sep 01, 2009 at 09:12:43AM -0700, Roland Dreier wrote: > > > I'm not really sure we should be trying to force drivers to share just > > > because they are paravirtualized -- if there is real commonality, then > > > sure put it in common code, but different hypervisors are probably as > > > different as different hardware. > > > > I really disagree. This kind of virtualised drivers are pretty much > > communication protocols, and not hardware. As such, why design a new one? > > If there's an infelicity in the ibmvscsi protocol, it makes sense to > > design a new one. But being different for the sake of being different > > is just a way to generate a huge amount of make-work. > > > > The same thing can be said about pretty much anything. We don't have > single SCSI, network, etc driver handling every devices in their > respective class, I don't see why it would be different here. > A hypervisor presents the same interface to the guest OS (whether > it is Linux, Solaris or another OS) much like a piece of silicone > does and it may very well be different form other hypervisors. Nobody said you had to have the exact same driver for every hypervisor. What people are suggesting is that we look at commonalities in the interfaces both from a control plane point of view (transport class) and from a code sharing point of view (libscsivirt). However, all the hypervisor interfaces I've seen are basically DMA rings ... they really do seem to be very similar across hypervisors, so it does seem there could be a lot of shared commonality. I'm not going to insist on RDMA emulation, but perhaps you lot should agree on what a guest to hypervisor DMA interface looks like. James -- 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/