Re: [Xen-devel] [RFC] Virtual disk configuration, PV vs. emulated, backward compatibility etc

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Thu, 29 Jul 2010, Ian Jackson wrote:
> Stefano Stabellini writes ("Re: [Xen-devel] [RFC] Virtual disk configuration, 
> PV vs. emulated, backward compatibility etc"):
> > On Thu, 29 Jul 2010, Ian Jackson wrote:
> > > What if the domain has real sd* devices too ?  (pvscsi, pvusb + usb
> > > mass storage, passthrough, ...)
> > 
> > Clashes are theoretically possible but very hard to produce in practice.
> > We are "stealing" device names only for emulated IDE and SCSI disks, and
> > emulated SCSI disks don't even work at the moment. So you would need to
> > passthrough an IDE controller whose disks are configured as hd* (most
> > distros use sd* for IDE disks).
> 
> There are definitely people who are using emulated scsi disks; perhaps
> they just haven't updated yet.

I am not so sure about that

> 
> > I think we are doing exactly what the user asked us to: setting up an
> > hdX device; in these very unlikely scenarios the user knows what he is
> > doing and can change the configuration.
> 
> Well, no, they can't, because their bootloader probably doesn't
> understand anything besides what they're actually using.
> 

they only have to change the device name, not the device class

> Certainly stealing the major number for scsi disks seems quite
> dangerous.  pv-usb is hardly that unlikely a scenario.
 
we are not doing that for pvusb


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