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Re: [Xen-devel] per-domain passthrough/iommu options


  • To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>
  • From: Jan Beulich <JBeulich@xxxxxxxx>
  • Date: Fri, 26 Jul 2019 14:01:49 +0000
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  • Thread-topic: [Xen-devel] per-domain passthrough/iommu options

On 26.07.2019 15:39, Paul Durrant wrote:
> Not sure how 'on' would co-exist with 'viommu'... the crucial difference is 
> whether the p2m is shared or not and the currently the only option in the 
> non-shared case, because we lack a viommu, is to keep the IOMMU mappings in 
> sync with the P2M whenever the latter is updated. So, how about:
> 
> passthrough = off|sync-pt|share-pt|viommu
> 
> ? I don't think 'private-pt' or 'separate-pt' really capture the fact that 
> the page tables match the P2M. They could just as easily be taken to mean 
> that they are populated using some other policy.

But haven't we recently seen that this fully lock-step population
of page tables isn't always correct (or at least desirable)? I
vaguely recall other comments to that effect too, from long ago.
I'd specifically want to avoid encoding into the interface here
that the two are exact mirrors of one another, now and forever.

Jan
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