Re: [Xen-devel] [rfc 00/18] ioemu: use devfn instead of slots as the unit for passthrough

[Simon Horman <horms@xxxxxxxxxxxx>]

On Thu, Mar 05, 2009 at 09:26:18AM +0000, Keir Fraser wrote:
> On 05/03/2009 09:05, "Simon Horman" <horms@xxxxxxxxxxxx> wrote:
> 
> > * I have not accounted for MSI devices/functions at this time,
> >   but my understanding is that they don't need a GSI at all.
> >   So it should be just a matter of giving them a device
> >   and making sure nothing else uses it.
> 
> Depending on how critical your no-sharing-between-passthru-devices is, you
> might need to be careful with this. Just because a device is MSI-capable
> doesn't mean the guest OS will use it (I don't know how common that would be
> in practice though!) -- generally there will be a legacy INTx operation mode
> which you might want to consider allocating GSIs for. Just a point of
> information.

That is a very good point. I suspect that will mean that we need
to assume that INTx will be used and thus MSI won't be a special case.

-- 
Simon Horman
  VA Linux Systems Japan K.K., Sydney, Australia Satellite Office
  H: www.vergenet.net/~horms/             W: www.valinux.co.jp/en


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