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

[James Courtier-Dutton]

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
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