Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755003AbZIAQIs (ORCPT ); Tue, 1 Sep 2009 12:08:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754829AbZIAQIr (ORCPT ); Tue, 1 Sep 2009 12:08:47 -0400 Received: from mail-yw0-f188.google.com ([209.85.211.188]:55617 "EHLO mail-yw0-f188.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753007AbZIAQIq convert rfc822-to-8bit (ORCPT ); Tue, 1 Sep 2009 12:08:46 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=XTTKvZNPCWFxE4rD17ixFXtoqXbZEoGgtoKGTb1Xu9htEZWMf6+wiNL6bauk/CYpF3 vS1/UVEegL/itPQ3OnJBxde/sti2RONAVo+mi8ywtv3zbY5Ax5jt0oV3LRFgDhp9vEeO hRaBSkPJ0RPeJZko6tiBQw5xzM510C0Rq5CE8= MIME-Version: 1.0 In-Reply-To: <1251815012.3864.55.camel@mulgrave.site> References: <1251415060.16297.58.camel@ank32.eng.vmware.com> <1251739735.16169.20.camel@ank32.eng.vmware.com> <1251741624.18828.83.camel@mulgrave.site> <1251755593.16169.51.camel@ank32.eng.vmware.com> <1251815012.3864.55.camel@mulgrave.site> Date: Tue, 1 Sep 2009 09:08:48 -0700 Message-ID: <35f686220909010908k24f0164nc09b1158b6841ff3@mail.gmail.com> Subject: Re: [PATCH] SCSI driver for VMware's virtual HBA. From: Alok Kataria To: James Bottomley Cc: akataria@vmware.com, Robert Love , Randy Dunlap , Mike Christie , "linux-scsi@vger.kernel.org" , LKML , Andrew Morton , Dmitry Torokhov , Rolf Eike Beer , Maxime Austruy , Bhavesh Davda Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2812 Lines: 72 Hi James, On Tue, Sep 1, 2009 at 7:23 AM, James Bottomley wrote: > On Mon, 2009-08-31 at 14:53 -0700, Alok Kataria wrote: >> Hi James, >> >> Thanks for your comments. >> >> On Mon, 2009-08-31 at 11:00 -0700, James Bottomley wrote: >> > On Mon, 2009-08-31 at 10:28 -0700, Alok Kataria wrote: >> > > VMware PVSCSI driver - v2. >> > >> > OK, so the first thing that springs to mind is that we already have one >> > of these things: the ibmvscsi ... is there no way we can share code >> > between this and the other PV drivers? >> >> I took a quick look at the ibmvscsi driver, and there are lot of >> differences between the two, mainly the ABI that is shared between the >> hypervisor and driver differ. > > Well, that's pretty abstractable, surely? ?However, there is an > interesting question of what the best hypervisor interface actually is. > >> ?Also the ibmvscsi driver seems to offer a >> lot of other features as well, like the SRP. > > SRP is the protocol transfer abstraction. ?It's just a way of packaging > up SCSI commands for transfer over a DMA protocol (OK, so it was > envisaged that the DMA protocol would be RDMA, but a hypervisor > interface is also a DMA protocol). > >> The pvscsi driver is a simple SCSI adapter driver and is basically no >> different than any other SCSI driver written for a particular HBA. > > Well, it is really ... hopefully all the hypervisor interfaces won't > decide to be completely incompatible, so there's a good chance of code > sharing between them. Well, going by that theory every SCSI driver can share some code with any other SCSI driver, In short we can come up with an low level SCSI driver interface which every SCSI driver can make use of, to reduce code duplicity. We don't do that, and the reason being, that its a device and we shouldn't expect every device to share common features or design decisions. We already virtualize storage at the lowest (read device) level to avoid duplicating stuff in a guest operating system. If this was say a block level virtaulizing scheme sharing would be more eminent, but given that we are a device its better to keep things separate and IMHO, it might be an overkill to design a new pv-driver or some such layer for every device that you virtualize. Thanks, Alok > > 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/ > -- 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/