Re: [PATCH] Add I/O hypercalls for i386 paravirt

James Courtier-Dutton
2007-08-22T22:25:54Z

Jeremy Fitzhardinge wrote:
> Zachary Amsden wrote:
>> This patch provides hypercalls for the i386 port I/O instructions,
>> which vastly helps guests which use native-style drivers. For certain
>> VMI workloads, this provides a performance boost of up to 30%. We
>> expect KVM and lguest to be able to achieve similar gains on I/O
>> intensive workloads.
>
> Two comments:
>
> - I should dust off my "break up paravirt_ops" patch, and this would fit
> nicely into it (I think we already discussed this)
>
> - What happens if you *don't* want to pv some of the io instructions?
> What if you have a device which is directly exposed to the guest?

If one could directly expose a device to the guest, this feature could
be extremely useful for me.
Is it possible? How would it manage to handle the DMA bus mastering?

James