From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751403Ab2GZJ6s (ORCPT ); Thu, 26 Jul 2012 05:58:48 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49096 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751040Ab2GZJ6r (ORCPT ); Thu, 26 Jul 2012 05:58:47 -0400 Message-ID: <501114D3.8090402@redhat.com> Date: Thu, 26 Jul 2012 11:58:43 +0200 From: Paolo Bonzini User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: James Bottomley CC: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: [PATCH 1/2] virtio-scsi: fix parsing of hotplug/hot-unplug LUN number References: <1342454751-8950-1-git-send-email-pbonzini@redhat.com> <1342454751-8950-2-git-send-email-pbonzini@redhat.com> <1343292731.3115.17.camel@dabdike> <50110820.4040403@redhat.com> <1343294472.3115.22.camel@dabdike> <50110D8C.8060802@redhat.com> <1343295687.3115.27.camel@dabdike> In-Reply-To: <1343295687.3115.27.camel@dabdike> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 26/07/2012 11:41, James Bottomley ha scritto: > On Thu, 2012-07-26 at 11:27 +0200, Paolo Bonzini wrote: >> Il 26/07/2012 11:21, James Bottomley ha scritto: >>>>> Because scsilun_to_int does not do the AND, so it would have exactly the >>>>> same bug I'm fixing. >>> It's not a bug ... it's the encoding. All the other devices use this >>> too. Ideally we should have switched to 64 bit lun numbers for the >>> encoding to be exact, but nothing so far has gone over 32 bits. If we >>> don't encode the Address method as part of the lun number, we don't get >>> the reverse transform right and the addressing often fails. >> >> But virtio-scsi gets it right even if you use method=0 and method=1 >> interchangeably. > > I don't actually understand this statement. LUNS < 256 may be encoded > either way (they should be encoded with address method=0 but they don't > have to be) if you address the array with the wrong method, it doesn't > have to give you your lun. But virtio-scsi does, LUN "16384" and LUN 0 are the same. If somebody wanted to add support for >16383 LUNs, we would do it with the 4-byte encoding that is in SAM, but I don't see that happening. > It's nothing to do with buggy hardware ... Hardware that knows about format=1 LUNs, and yet treats LUN 0 differently depending on the encoding sounds buggy. Of course some hardware may not know anything about format=1, so it is wrong to pass format=1 unconditionally, but virtio-scsi does. Paolo