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

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?


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