* Daniel P. Berrange <berrange@xxxxxxxxxx> wrote: > On Mon, Mar 22, 2010 at 02:31:49PM +0200, Pekka Enberg wrote: > > On Mon, Mar 22, 2010 at 1:48 PM, Ingo Molnar <mingo@xxxxxxx> wrote: > > >> What about line number information? ?And the source? ?Into the kernel with > > >> them as well? > > > > > > Sigh. Please read the _very first_ suggestion i made, which solves all that. I > > > rarely go into discussions without suggesting technical solutions - i'm not > > > interested in flaming, i'm interested in real solutions. > > > > > > Here it is, repeated for the Nth time: > > > > > > Allow a guest to (optionally) integrate its VFS namespace with the host side > > > as well. An example scheme would be: > > > > > > ? /guests/Fedora-G1/ > > > ? /guests/Fedora-G1/proc/ > > > ? /guests/Fedora-G1/usr/ > > > ? /guests/Fedora-G1/.../ > > > ? /guests/OpenSuse-G2/ > > > ? /guests/OpenSuse-G2/proc/ > > > ? /guests/OpenSuse-G2/usr/ > > > ? /guests/OpenSuse-G2/.../ > > > > > > ?( This feature would be configurable and would be default-off, to maintain > > > ? ?the current status quo. ) > > > > Heh, funny. That would also solve my number one gripe with virtualization > > these days: how to get files in and out of guests without having to > > install extra packages on the guest side and fiddling with mount points on > > every single guest image I want to play with. > > FYI, for offline guests, you can use libguestfs[1] to access & change files > inside the guest, and read-only access to running guests files. It provides > access via a interactive shell, APIs in all major languages, and also has a > FUSE mdule to expose it directly in the host VFS. It could probably be made > to work read-write for running guests too if its agent were installed inside > the guest & leverage the new Virtio-Serial channel for comms (avoiding any > network setup requirements). > > Regards, > Daniel > > [1] http://libguestfs.org/ Yes, this is the kind of functionality i'm suggesting. I'd suggest a different implementation for live guests: to drive this from within the live guest side of KVM, i.e. basically a paravirt driver for guestfs. You'd pass file API guests to the guest directly, via the KVM ioctl or so - and get responses from the guest. That will give true read-write access and completely coherent (and still transparent) VFS integration, with no host-side knowledge needed for the guest's low level (raw) filesystem structure. That's a big advantage. Yes, it needs an 'aware' guest kernel - but that is a one-off transition overhead whose cost is zero in the long run. (i.e. all KVM kernels beyond a given version would have this ability - otherwise it's guest side distribution transparent) Even 'offline' read-only access could be implemented by booting a minimal kernel via qemu -kernel and using a 'ro' boot option. That way you could eliminate all lowlevel filesystem knowledge from libguestfs. You could run ext4 or btrfs guest filesystems and FAT ones as well - with no restriction. This would allow 'offline' access to Windows images as well: a FAT or ntfs enabled mini-kernel could be booted in read-only mode. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
