Re: [Xen-devel] Future support of 5-level paging in Xen:wq

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.12.16 at 04:57, <liang.z.li@xxxxxxxxx> wrote:
> 1.  Should we enable 5 level paging for PV guest ? (You are discussing)

Personally I think we should, but as you say - we haven't settled on
this yet.

> 2.  Should we make the 5 level paging and 4 level paging supported with one 
> binary?

May I suggest to make this dependent on (possibly among other
aspects) how much of an impact the switch from using constants
to using variables has on the various code paths, namely hot ones?
Quite possibly the most flexible approach would be a Kconfig choice
between 3 build flavors (static 4 levels, static 5 levels, runtime
determined), which I would hope to not end up in too ugly overall
source code.

> 3.  When should the 5 level EPT be enabled?

I think the suggestion to avoid 5 levels when not needed for a guest
is quite reasonable. In fact, if hardware allows it, using just 3 levels
for not too big guests could be an option, too.

> 4. Should we extend shadow page to support 5 level paging guest?

That to a large part depends on what we settle on for 1).

Jan


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