Re: Starting save/restore for port-xen - initial questions

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Wed, Mar 12, 2008 at 01:43:19PM +0100, Jean-Yves Migeon wrote:
> On Tue, 11 Mar 2008 16:09:48 +0100, Manuel Bouyer 
> <bouyer%antioche.eu.org@localhost>
> wrote:
> >> You can test at runtime with xm block-attach/detach and xm
> >> network-attach/detach.
> > 
> > This is already working. But it's a bit different from suspend:
> > with xm foo-detach, the device will dissapear on the domU side too
> > (just like if you had unplugged your USB key, or PCMCIA network
> > interface).
> > For suspend/resume we want the devices to stay here. If after resume
> > the block device instance changed, the mounted filesystems will become
> > invalid (which is annoying for / :). The same goes for IP addresses and
> > ethernet devices.
> 
> Hmmm, BTW, what should happen in such a scenario? End in panic() while
> resuming the image, as / does not match?

Either the block-device was detached, and in this case any operation
will abort with EIO (the VFS code will take care of this), or the
content of the block device changed without the device being
detached/reattached, and the system will sooner or later panic within
the filesystem code.

> 
> I guess that resuming with an invalid IP or ethernet device is acceptable
> for the guest, but what about block devices?

Yes, no problems for ethernet devices, it just has to have been properly
detached.

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           
Manuel.Bouyer%lip6.fr@localhost
     NetBSD: 26 ans d'experience feront toujours la difference
--