RE: [Xen-ia64-devel] [RFC][PATCH] [RESEND] support special guest optimisations in the hypervisor

[Alex Williamson <alex.williamson@xxxxxx>]

On Fri, 2007-07-06 at 09:01 +0800, Xu, Anthony wrote:
> Hi Dietmar,
> 
> I can understand you want to use the same interface for special guest 
> Optimizations. While I think it is OK to use different interfaces for HVM and 
> domU.
> So I suggest HVM still use interface like GOS_WINDOWS(v), while domU uses 
> opt_feature interface.

Hi Anthony,

   From a maintenance perspective, it's much nicer to use the same
interface for both PV and HVM.  In this case, it seems like it's even
fairly easy to do so.  Do you have any specific objections to using a
feature bit versus an OS identifier?  Personally I like the idea of
tuning based on a property of the guest OS instead of the type of guest
OS.  It's also more self explanatory in the code that a guest has
feature X, therefore we can optimize Y.  Tuning based on IS_WINDOWS() is
more opaque.

Dietmar, is there any reason to use "PV" or "HVM" in the name of the
feature bit?  It seems like if we had a OPTF_IDENT_MAP_HVM_REG7 and a
OPTF_IDENT_MAP_PV_REG7 that they wouldn't intersect in usage.  We could
therefore make them the same bit and drop the extra identifier.  In the
Windows case, I wonder if that should be two separate bits for region 4
& 5 instead of combining them into one.  Thanks,

        Alex
 
-- 
Alex Williamson                             HP Open Source & Linux Org.


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