Re: [Qemu-devel] Re: [PATCH] virtio-blk: assign a default serial number if none provided

[Michael S. Tsirkin]

On Wed, Jun 02, 2010 at 06:45:46AM -0500, Ryan Harper wrote:
> * Michael S. Tsirkin <address@hidden> [2010-06-02 04:08]:
> > On Tue, Jun 01, 2010 at 08:48:54PM -0500, Ryan Harper wrote:
> > > This patch applies on-top of John's virtio-blk serial patches.
> > > 
> > > Generate default serial numbers for virtio drives based on DriveInfo.unit 
> > > which is
> > > incremented for each additional virtio-blk device.  This provides a
> > > per-virtio-blk number to use in the default string: QM%05d that is used in
> > > hw/ide/core.c.  The resulting serial number looks like: QM00001, etc.
> > > 
> > > Signed-off-by: Ryan Harper <address@hidden>
> > 
> > 
> > I think that there's a problem with this approach in that hot plug A,
> > hot plug B, hot unplug A is not the same as hot plug B.
> > So you might get guest boot failures and no easy way to
> > figure out why. For guests that need S/N, I think they
> > really must be persistent.
> 
> That's true; though I think most boot drives boot via either LVM or UUID
> which will remain persistent.  That said, if you are relying on the
> by-id; then of course the user will need to specify serial versus having
> one auto-generated.

I guess the question then would be, if you don't rely on the S/N, why
do you want to set it?

> -- 
> Ryan Harper
> Software Engineer; Linux Technology Center
> IBM Corp., Austin, Tx
> address@hidden