Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752964Ab2BGO3G (ORCPT ); Tue, 7 Feb 2012 09:29:06 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42272 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750836Ab2BGO3D (ORCPT ); Tue, 7 Feb 2012 09:29:03 -0500 Message-ID: <4F313526.2050907@redhat.com> Date: Tue, 07 Feb 2012 15:28:54 +0100 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:9.0) Gecko/20111222 Thunderbird/9.0 MIME-Version: 1.0 To: Christian Hoff CC: BORNTRAE@linux.vnet.ibm.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, mst@redhat.com, rusty@rustcorp.com.au Subject: Re: Pe: [PATCH v5 1/3] virtio-scsi: first version References: <4F30F4EE.4080607@redhat.com> <4F311154.9080407@de.ibm.com> <4F3119A0.7080005@redhat.com> <4F312492.1040002@de.ibm.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 31 On 02/07/2012 02:59 PM, Christian Hoff wrote: > Instead the format has some disadvantages: > - It uses up 8 bytes where 3 bytes would be sufficient in order to store > both the target ID and LUN number information > - The format limits us to 255 target IDs. I agree that the LUN limit is > probably more a theoretical and not a practical one, but 255 target IDs > could become a limitation in the future. It also provides better upwards-compatibility in case the limitations are actually hit. If I had used "uint8_t target; uint16_t lun;" an extension would require a feature bit and a new struct. With 8-bytes, you can just expand the definition. That pretty much sums it up. But again, I don't think the limitations are serious. A MegaSAS header has room for 256 targets too, VMWare has only 15, Hyper-V has 1 (and 2 channels, but I think that's an off-by-one), and you can always have multiple HBAs on the same guest. > Nonetheless I think that virtio-scsi is a useful project and addresses > many of the limitations imposed by virtio-block. The fact that I am still > persisting has more to do with interest in the project rather than wanting > to keep the code from going upstream. No problem. :) Paolo -- 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/