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[Xen-devel] [PATCH] Xen Guest Kexec

To: xen-devel@xxxxxxxxxxxxxxxxxxx, fastboot@xxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH] Xen Guest Kexec
From: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Date: Thu, 7 Jul 2005 18:16:28 +0100
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I'm posting to the Xen-devel list and the OSDL fastboot list.  There are a 
number of Xen folks who'll want to look at the code.  For the fastboot folks, 
this is mostly intended as an announcement of the port.  Please limit your 
replies to the list(s) that they applies to, thanks :-)

A number of people have expressed interest in kexec support for Xen guests.  
In particular, it's mainly useful for purposes of implementing an in-guest 
bootloader app and avoiding the need for dom0 to access the guest filesystem.

It's a largish patch, so I stuck it online: 
Tested on i386.  I suspect it'll have build issues on x86_64 but those should 
be easy to fix - actually the code is probably generic enough to work on 

You'll also need a modified version of the kexec tools, which I'll post 
details of later.

Notes on the implementation:
Kexec in a Xen guest doesn't work like on a real machine.  The guest relies on 
outside assistance to complete the job.  The guest communicates details of 
the kexec to Xend.  Xend extracts the data from the guest's memory image and 
uses it to rebuild the domain with a new kernel, etc.  This approach 
simplifies the changes needed to support kexec and minimises code duplication 
between Linux and the domain builder itself.

Kexec-ing the whole host is a separate issue, I think it's best addressed with 
a port of kexec to Xen itself.


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