[Xen-devel] RE: Building domains as a lesser user (was Re: [Xen-devel] bootloaders for domain != 0)

[Jeremy Katz <katzj@xxxxxxxxxx>]

On Fri, 2005-02-04 at 09:38 +0000, Ian Pratt wrote:
> > On Fri, 2005-02-04 at 02:30 +0000, Ian Pratt wrote:
> > Especially as you start thinking about things like modular fs's, etc,
> > it's going to be much less clean of a solution and be a significant
> > slowdown on your guest boot time.
> 
> A few seconds slow down -- nothing compared to what a BIOS normally
> adds.
> 
> I don't see why the filesystems would particularly need to be modular,
> though you might do so for convenience. 

Because if the kernel is _different_ than every other kernel being
shipped by a distribution, then it's a major pain.  It also ends up
giving people a lot less flexibility (because if I were to do that, for
example, it would only have ext[23] support leaving users of
reiserfs/xfs/jfs/foofs out in the cold whereas with a modular solution,
they can at least add the support for what they want).

> > And then, it's yet another kernel to keep updated, etc.
> 
> I don't see any reason to keep it up to date. Its running in a protected
> environemnt and doesn't have any extra access that the kernel about to
> be booted is going to get.

Users don't tend to take that answer very well ;)  The protected
environment means you can have a little bit longer to fix it, but they
have things like audit requirements, etc.  And just because it's running
in a protected environment doesn't mean it's bug-free.  Or that it's
going to be able to stand still as filesystem features are added, etc.
This ends up being less of a concern with minimalistic implementations
for reading filesystems like grub's and libext2fs.

Jeremy



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