Re: Xen bootloader (was: Re: [Xen-devel] Xen Roadmap proposal)

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > Which OSes are you thinking of here?  Linux currently supports (assuming
> > it works well enough for read access) the boot filesystems of everything
> > that runs on Xen, plus more.
>
> Presuming they all work well enough. Stuff like UFS is the sort of
> corner code that doesn't get much love, because so few people use it.
> Making boot rely on it not breaking seems worrying. To some degree, the
> same goes for FAT.

I think FAT'll be OK - it has to work reasonably well for people with digital 
cameras, MP3 players, etc.

I agree UFS is a bit less likely to be well maintained, but I imagine if read 
support works it's relatively unlikely to break...  It's something that 
probably would merit investigation before anyone tries to mandate a standard 
Xen bootloader (if, indeed, that is a good idea in the first place).

> > It's a fair point that it increases effort for OS maintainers if they
> > have a grub driver for a filesystem that Linux doesn't already support -
> > I'm not clear what this could be though.  Are you thinking about ZFS,
> > perhaps?
>
> Yes.

Really, with a suitable bootsequence we could probably have a much more 
guest-based bootloader setup such that users could specify their own 
bootloader using a "boot block", which could be quite a nice compromise.

The ZFS-FUSE stuff looks like it might help with this, since in userspace it's 
able reuse the Solaris code without licensing worries.  However, it's still 
in the pipeline, without a guaranteed completion date (although it *ought* to 
work by the SoC deadline, there's not a lot else to do other than cross 
fingers here).

Until somebody produces a Xenified version of Grub it looks like the most 
straightforward solution for most people is to use pygrub and friends, or try 
kboot if they're feeling adventurous.  Once a Grub/Xen version is available I 
guess we can weight up the pros/cons of different approaches then.

I assume you're using Grub 1 - if it were based on Grub2 presumably the ZFS 
driver would still need porting?

Cheers,
Mark

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