Re: Proposal for init/kexec/hotplug format for Xen

[Anthony Liguori <aliguori@us.ibm.com>]

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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