From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH] Fix restore handling checks Date: Wed, 23 Jun 2010 13:19:01 +0200 Message-ID: <4C21EDA5.5070100@redhat.com> References: <4C204D8C.3020303@redhat.com> <19488.53018.201328.781032@mariner.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <19488.53018.201328.781032@mariner.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Jackson Cc: Michal Novotny , "'xen-devel@lists.xensource.com'" , Keir Fraser List-Id: xen-devel@lists.xenproject.org On 06/22/2010 04:56 PM, Ian Jackson wrote: > Michal Novotny writes ("Re: [Xen-devel] [PATCH] Fix restore handling checks"): >> Right, there's the exception for CD-ROMs according to the spec. I should >> implement this as well but read-only IDE disk devices are not supported >> according to the IDE specs. > > I don't think this is a very good argument for not supporting them. > > The Xen administrator should be able to present a guest with an IDE > disk and nevertheless prevent the guest from writing to it. > > If that means that the guest administrator needs to be told > out-of-band that writes will not work, rather than having their kernel > automatically discover the read-only nature, then that's fine. And if > the guest administrator doesn't do that and their kernel tries to > write and gets IDE errors then that is the correct consequence. We tried to get that to work, and we could not really find a device error that worked reliably in the guests. We often got infinite loops on mount or little after that, on both Linux and Windows. If you want to use read-only devices, you should really use SCSI or PV devices. Paolo