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

Rusty Russell
2008-03-23T12:05:37Z

On Friday 21 March 2008 01:11:35 Anthony Liguori wrote:
> Rusty Russell wrote:
> > There are three possible solutions:
> > 1) Just offer the lowest common denominator to both sides (ie. no
> > features). This is what I do with lguest in these patches.
> > 2) Offer something and handle the case where one Guest accepts and
> > another doesn't by emulating it. ie. de-TSO the packets manually.
> > 3) "Hot unplug" the device from the guest which asks for the greater
> > features, then re-add it offering less features. Requires hotplug in the
> > guest OS.
>
> 4) Add a feature negotiation feature. The feature that gets set is the
> "feature negotiate" feature. If a guest doesn't support feature
> negotiation, you end up with the least-common denominator (no
> features). If both guests support feature negotiation, you can then add
> something new to determine the true common subset.

Hmm, I discarded that out of hand as too icky, but we might end up there.
Analyse features like normal, accept feature negotiation, set DRIVER_OK, wait
for config change, if feature negotiation is still set then go around again
(presumably some features have been removed).

I'll prototype it and see how we go.

Thanks,
Rusty.

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