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Re: [Xen-users] kexec into a new Dom0 Xen kernel possible?

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Subject: Re: [Xen-users] kexec into a new Dom0 Xen kernel possible?
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Wed, 2 Nov 2005 12:17:16 +0000
Cc: fastboot@xxxxxxxxxxxxxx, "Andreas Bach Aaen \(AH/TED\)" <andreas.bach.aaen@xxxxxxxxxxxx>
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> I have puzzled with the idea if it's possible to upgrade a Dom0 XEN kernel
> by using kexec. Of cause the x86-xen architecture isn't supported by kexec
> yet, but is it in principle possible?


> The XEN microkernel should continue to run, and the new Dom0 kernel should
> somehow be connected to XEN, so is will be able to manage it. If the table
> of user domains are kept inside XEN and not the dom0 kernel they should be
> able to continue to run during this kexec fastboot.

Well yes...  You'll have to reconnect the device channels though.  This'll 
also require the tools to save their state persistently across the dom0 

When I worked on kexec my feeling was that it might be easier to build a kexec 
into Xen that restarts the whole host.  If you really want to, restarting 
dom0 would be done by "failing over" to a standby domain 0 - we'd talked 
about having this feature for robustness to dom0 crashes anyhow.

My kexec for domUs was nice in that it required (comparatively) minimal code 
duplication, since it was "assisted" by daemon in domain 0.  The patch still 
exists but has rotted from being out-of-tree so long.


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