RE: [Xen-devel] [Patch] Qemu map cache

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

> Have you considered doing something similar for mainline QEMU?  The
> reason I ask is that V2E pulls in all of the dynamic translation code.
> My initial reaction is that doing map cache will require a significant
> amount change to the dynamic translation bits since we can no longer
> make the assumption that memory can be accessed directly.  I don't
fully
> have my head around it yet, but this may involve lots of nastiness
with
> keeping track of which TB's reference what memory and invalidating
those
> TBs when map cache references are invalidated.  The QEMU TLB may
> simplify some of this but I'm not entirely sure.
> 
> Have you given this any thought?

Being able to invalidate (sections of) qemu's mappings (at least
asynchronously) is essential to allow the balloon driver to work for HVM
guests. V2E is going to have to bite the bullet on this one.

Of course, in a 64b environment the map cache can be direct mapped, but
you still need the ability to do invalidates. BTW: I'm comfortable if
V2E only works on 64b. Sooner or latter there's going to be some new
feature which isn't supported on Yonah...

Ian

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