Re: /kern/xen in domU?

[Jean-Yves Migeon <jeanyves.migeon%free.fr@localhost>]

On Wed, 21 Sep 2011 12:33:18 +0100 (BST), Stephen Borrill wrote:
> On a NetBSD guest, I installed xentools33 to give me the relevant
> xenstore tools and libraries, but /kern/xen doesn't exist on NetBSD 
> as
> a domU. Indeed, xenbus_probe_init() explicitly skips setting it up
> unless DOM0OPS is set.
>
> Any reason for this restriction?

No restriction, a domain should be able to use Xen tools to write 
information in its own subtree inside XenStore.

Explanations why it isn't:

IIRC about a year ago Andrew disabled kernfs because it would disappear 
eventually, replaced by a mix of sysctls, kvm(3) and /dev nodes. 
Unfortunately, there are entries required by dom0 to send or query 
information from Xen, created dynamically under /kern/xen.

As the current Xen tools do not have compat code to handle kernfs' 
disappearance, it stayed in but was not exposed to a wider audience 
(domUs). Retiring kernfs touches multiple parts, and will require compat 
code in Xen tools + modifying NetBSD, so unless this gets done for -6, 
it will be around for some time.

--
Jean-Yves Migeon
jeanyves.migeon%free.fr@localhost