Re: [Xen-devel] PVH and mtrr/PAT.........

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 22/11/13 11:09, Jan Beulich wrote:
> > > > On 22.11.13 at 11:43, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
> > I'm not incredibly familiar with the PAT / MTRR stuff, either from a
> > hardware level or a Xen level, so sorry if this is a dumb question. It
> > sounds like you're saying, because we have virtual MTRRs that are
> > already translated into EPT types, we should disable virtual MTRRs and
> > use PAT instead.  That doesn't make any kind of sense to me.  (I didn't
> > understand it when Jan said it either.)
> The underlying observation is that MTRRs aren't really needed -
> all they can do can be done with PAT. They pre-date PAT though,
> hence hardware vendors can't easily drop them. But in a model
> like PVH I just don't see the value of allowing their use, considering
> that this adds unnecessary complexity.
OK -- so when we move forward with the plan of "PVH mode is HVM mode 
with a couple of tweaks", you think that we should have an "enable 
virtual MTRR" flag, and disable this for PVH mode?
 -George

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