Re: [Xen-devel] [PATCH 7/8] x86/EPT: split super pages upon mismatching memory types

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.03.14 at 16:04, <tim@xxxxxxx> wrote:
> At 15:36 +0000 on 26 Mar (1395844618), Jan Beulich wrote:
>> ... between constituent pages. To indicate such, the page order is
>> being passed down to the vMTRR routines, with a negative return value
>> (possible only on order-non-zero pages) indicating such collisions.
>> 
>> Some code redundancy reduction is being done to ept_set_entry() along
>> the way, allowing the new handling to be centralized to a single place
>> there.
>> 
>> In order to keep ept_set_entry() fast and simple, the actual splitting
>> is being deferred to the EPT_MISCONFIG VM exit handler.
> 
> You expect that to be rare, right?  We're not going to incur a lot of
> extra pagefaults?

Yes, since type changes are rare (normally limited to guest boot and
passthrough device hotplug).

Jan


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