Re: [Xen-devel] RFC: [0/2] Remove netloop by lazy copying in netback

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 27/3/07 12:11, "Herbert Xu" <herbert@xxxxxxxxxxxxxxxxxxx> wrote:

> OK, you got me there :)
> 
> Of course I'd still like to avoid this if possible since it introduces
> another change from Linux.

Yeah, that's fair enough. We've avoided PV-driver dependencies on changes in
core architectural code so far. It would be nice to continue this,
particularly given we now support PV-on-HVM (ie.,
PV-on-otherwise-unmodified-guest). Of course we'd only be introducing a
dependency for a *backend* driver here.

Your thought of using the accessed bit is rather neat. I believe it is
guaranteed that if we test-and-clear a pte, and see A==0, then no TLB can
cache that pte. If so, I think this could be a winner.

 -- Keir


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