[Lguest] Lguest modification.

ron minnich rminnich at gmail.com
Fri Oct 26 02:17:43 EST 2007


On 10/25/07, Sujit Sanjeev <sujit771 at gmail.com> wrote:

> 1. Store some data (variable or constant) in a host protected or hypervisor
> protected memory area, maybe in a page by itself.

you don't need to worry about this 'page' thing if there is not issue
of guest access.

>
> 2. If the guest needs the value of this variable, it must make a hypercall
> and the host must return the value. For this I would like to add a new
> hypercall.
>     Basically, I don't want the guest getting direct access to that
> variable, i.e. it should not be stored in the guest's memory address space.


You might look at a 9p server for this purpose. You could create an
in-kernel server that manages these variables. The variables can be
exported to the guest over a 9p-based virtio  connection. The guest
can mount that 9p connection somewhere in its file system. These
variables thus end up looking like a file system tree to the guest;
reading a variable can look like cat'ing a file. See Luchos' mods for
recent lguest support for in-kernel 9p servers. You could set up a
virtio server for your variables.

Just, please, don't
1. use XML as a data format
2. recreate the Xen store. The Xen store, while it seemed a good idea,
is a whole collection of lessons on what not to do.

ron



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