Re: [RFC PATCH 0/4] Inter-guest virtio I/O example with lguest

Rusty Russell
2008-03-20T22:14:05Z

On Thursday 20 March 2008 17:54:45 Avi Kivity wrote:
> Rusty Russell wrote:
> > Hi all,
> >
> > Just finished my prototype of inter-guest virtio, using networking as
> > an example. Each guest mmaps the other's address space and uses a FIFO
> > for notifications.
>
> Isn't that a security hole (hole? chasm)? If the two guests can access
> each other's memory, they might as well be just one guest, and
> communicate internally.

Sorry, sloppy language on my part. Each launcher process maps the other
guest's memory as well: ie. copying occurs in the host.

> My feeling is that the host needs to copy the data, using dma if
> available. Another option is to have one guest map the other's memory
> for read and write, while the other guest is unprivileged. This allows
> one privileged guest to provide services for other, unprivileged guests,
> like domain 0 or driver domains in Xen.

One having privilege is possible, even trivial with the current patch (it's
actually doing a completely generic inter-virtio-ring shuffle). I chose the
symmetrical approach for this demo for no particularly good reason.

Cheers,
Rusty.

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