Re: [Xen-devel] Re: [PATCH] Fix restore handling checks

[Michal Novotny <minovotn@xxxxxxxxxx>]

On 06/23/2010 02:35 PM, Alan Cox wrote:
> On Wed, 23 Jun 2010 13:29:56 +0200
> Michal Novotny<minovotn@xxxxxxxxxx>  wrote:
>
>    
> > On 06/23/2010 01:27 PM, Ian Jackson wrote:
> >      
> > > Paolo Bonzini writes ("Re: [PATCH] Fix restore handling checks"):
> > >
> > >        
> > > > 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.
> > > >
> > > >          
> > > That's fine.  If the admins don't want that then they can use SCSI or
> > > PV or simply not tell the guest to write to the device.
> > >
> > > Disallowing the configuration entirely just because the error handling
> > > is suboptimal (but safe!) is not correct.
> > >
> > > Ian.
> > >
> > >        
> > Why do you think so, Ian? This follows the IDE specifications to
> > disallow read-only IDE disks since the specs doesn't support IDE
> > read-only disks. The only read-only device being supported by IDE specs
> > is the CD-ROM device.
> >      
> IDE (or more properly ATA) doesn't support CD-ROM either. ATAPI does, and
> it also supports other ATAPI devices with write protect including magneto
> optical and floppy.
>
>
>    
Agreed Alan. This is right that ATAPI does. Nevertheless in IDE specs 
it's about ATA and ATAPI. The read-only file systems are supported for 
IDE drives only for floppy and tape media according to the linux kernel 
source codes. Also, CD-ROM devices can be read-only but no other IDE 
media, i.e. no IDE disks.
Michal

--
Michal Novotny<minovotn@xxxxxxxxxx>, RHCE
Virtualization Team (xen userspace), Red Hat


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