Re: Sharing variables/memory between host and guest ?

[Dor Laor <dor.laor@qumranet.com>]

Arn wrote:
> How can one share memory (a few variables not necessarily a page)
> between host/hypervisor and guest VM ?
> Since the guest is just a process within the host, there should be
> existing ways to do this.
>   
It's not that straight forward since the host has its pfn (page frame 
number) while the guest has gfn (guest frame number) and also use 
virtual memory.

> What about using something like debugfs or sysfs, is it possible to
> share variables this way ? Note, I want a system that
> is fast, i.e. changes to shared variable/memory should be visible instantly.
>
>   
A paravirtualized driver can take care of that with driver in the guest 
and device side in qemu/host kernel.
You can use 9p virtio solution in Linux that implements a shared file 
system.
> I search the kvm-devel archives and found emails referring to "kshmem"
>  but a search on the kvm-70 code turns up nothing.
> There are also some emails on sharing a page but no final outcome or
> what exactly to do.
>
> Thanks
> Arn
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