Re: [kvm-ppc-devel] KVM kernel/userspace TLB interface

[Hollis Blanchard <hollisb@us.ibm.com>]

On Wed, 2008-01-23 at 14:38 +0100, Christian Ehrhardt wrote:
> Christian Ehrhardt wrote:
> 
> This mail now has the reworked implementation of the patch for ppc440
> in the #2 style attached where the guest tlb can be get/set completely
> and the shadow tlb can be read from userspace (now separate ioctls for
> guest/shadow).

I don't think the host userspace should ever need to directly manipulate
the shadow TLB state. IIRC x86 just has a "sync shadow MMU state"
command (not sure what it does or when you use it though).

I also really don't like accessing the whole TLB as a giant array when
single-entry commands would work just fine.

> Actually this should work for most if not all use cases we have.
> Especially our current use case of setting up a proper initial state
> is very arch dependent anyway and if we really can save userspace code
> for shared usage depends on the fact if we will be able to create a
> shared bit format for flags (I start to put a common "map this" call
> down on my prio list).

"Flags" could just indicate IO vs RAM mappings. That would be nice and
generic. If IO flag is set, the host would map with
cache-inhibited/guarded. If not, it's a RAM mapping, so don't.

-- 
Hollis Blanchard
IBM Linux Technology Center


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