On Wed, Jul 18, 2007 at 10:40:48AM +0100, Richard W.M. Jones wrote:
Hugh Brock wrote:
I'm looking at ways to replicate xm block-configure at the libvirt level. xm block-configure is useful in that it allows you to change the back device for an HVM guest while the guest is still running; this permits you for example to change the CDROM without shutting down your guest or poking around in xenstore. Thus we can have an "eject" button on cdrom devices in virt-manager (or "eject" and "load" buttons, I guess), which we really need.
The issue of course is that xm block-configure is specifically intended for block devices and takes arguments for the back device and the front device (among others). We would naturally prefer to accept a block of XML just as virDomainAttachDevice does and then parse it, determine if the device in question is of a type we can actually edit, determine if the new backdev is appropriate, and so on.
Definitely this will be useful for USB ...
I think the question is: Should we have another entry point (virDomainConfigureDevice), or should we just modify virDomainAttachDevice so that if it sees XML for a device which is already attached it just modifies the device?
I don't mind too much either way. The only benefit a separate entry point would give is ability for an app to get an error back if they tried to modify a device which didn't exist. Whether they're separate or same entry point the underlying impls will be able to share a reasonable amount of code.
None of this seems terribly hard, but before I go implement it, are there obvious pitfalls I'm not thinking? And given that virDomainAttachDevice is not implemented for qemud in libvirt (is it?), how do we handle the non-xen case?
It seems like it isn't implemented for qemud. Changing the CD-ROM is possible through the qemu monitor, so it should be.
I intend to implement it when adding support for USB disk & device passthrough in QEMU/KVM. It will use the monitor for adding/removing USB devices on the fly. Likewise we can do CDROM media changes this way. Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|