Re: [PATCH 1/1] direct mmio for passthrough - kernel part

[Avi Kivity <avi@qumranet.com>]

Anthony Liguori wrote:
> What about switching the KVM MMU code to use hfn_t instead of struct 
> page? The initial conversion is pretty straight forward as the places 
> where you actually need a struct page you can always get it from 
> pfn_to_page() (like in kvm_release_page_dirty).
>
> We can then teach the MMU to deal with hfn_t's that don't have a 
> corresponding page.  IIUC, the implementation of something like 
> kvm_release_page_dirty is a nop for pfn's that don't have a 
> corresponding page.  We just have to be able to detect a pfn_to_page() 
> failure and then assume we're dealing with IO memory.
>
>   

It ought to work.  gfn_to_hfn() (old gfn_to_page) will still need to 
take a refcount if possible.

This will increase the potential for type errors, so maybe we need to 
make gfn_t and hfn_t distinct structures, and use accessors to get the 
actual values.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.


-------------------------------------------------------------------------
Check out the new SourceForge.net Marketplace.
It's the best place to buy or sell services for
just about anything Open Source.
http://ad.doubleclick.net/clk;164216239;13503038;w?http://sf.net/marketplace