Re: [Xen-devel] How to detect HAP from DomU?

[Keir Fraser <keir@xxxxxxx>]

On 10/11/2010 08:22, "Juergen Gross" <juergen.gross@xxxxxxxxxxxxxx> wrote:

> is there any way for a HVM-domain to detect whether it is running with HAP
> enabled? I couldn't find any interface for this information.
> 
> Background: in our BS2000 domain (HVM with PV-drivers) we sometimes have to
> copy complete pages between kernel and user. An alternative to the copy
> would be a remapping of the page. The remap is faster than the copy with HAP
> enabled, but much slower without HAP. So it would be best to copy without HAP
> and remap with HAP.

You could do a few remaps and copies and see how long it takes? Has the
advantage that you aren't tied up to one policy based on one system's
timings for those particuler ops. I don't think basing policy on static
assumptions about hidden implementation features is a good idea.

 -- Keir



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