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Re: [Xen-devel] Proposal for init/kexec/hotplug format for Xen

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Proposal for init/kexec/hotplug format for Xen
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Sun, 27 Feb 2005 09:25:42 -0600
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Jeremy Katz <katzj@xxxxxxxxxx>, Xen Mailing List <xen-devel@xxxxxxxxxxxxxxxxxxxxx>
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Keir Fraser wrote:

For kexec and bare-metal bringup, the PPC64 port uses a fairly simple
header + flattened tree of keyword/value pairs (on PPC64, used to hold
the Open Firmware tree plus Linux extras).  This offers flexibility for
new virtual devices, etc; I propose that we adopt this format or
something very similar for Xen, first by putting a pointer into it in
start_info_t, and then migrate entries across as appropriate.


I like the idea of bringing out device discovery, bringup, teardown, recovery all into its own driver or subsystem -- it seems the obvious way to go. But I think the 'device tree' should be in the to-be-designed persistent store, and we publish an interface to allow guests to peek/poke that store.

I think publishing domain-information in an OF-like tree would be great.

I think we want the persistent store to be outside the OF-tree though. It would provide a good buffer against ill-written management apps.

The way I envision this working is to have a persistent store in user-space on a priviledged domain that exported within it's tree the OF device-tree. This way management app information (the domain's name, an icon associated with it, etc.) would not be stored in the OF tree. If you needed to blow away a portion of the store because of an misbehaving management app you do not lose any of the vital device information.

Does PPC64 or rHype provide a mechanism to notify user-space daemons when a value in the tree changes?

I think this is a great proposal.

Regards,
Anthony Liguori

 -- Keir



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