Xen devel - Apr 2008 - Re: [PATCH][RFC] Supporting EnlightenedWindows2008Server

>>> On Mon, Apr 7, 2008 at 11:15 AM, in message
<C41FF920.1EDFD%keir.fraser@eu.citrix.com>, Keir Fraser
<keir.fraser@eu.citrix.com> wrote: 
> On 7/4/08 15:28, "Ky Srinivasan" <ksrinivasan@novell.com>
wrote:
> 
>>> It''s certainly quite a bit shorter which is good. For the
remaining stuff,
>>> do you have empirical evidence that performance is improved by it?
>>> 
>> I do. On the NetBench runs we did, we were seeing close to 10%
improvement.
> I
>> will keep you posted on other benchmark results as they become
available.
>> Furthermore, as MSFT defines new enlightenments, we can implement those
>> cleanly within this body of code. Additionally, there is value in
claiming
>> that we support all the enlightenments needed for hosting enlightened
win
> 2008
>> servers.
> 
> Do you know which hypercalls that benefit comes from? HV_GET_VP_REGISTERS
see no reason to
> support more hypercalls than necessary (I certainly don''t see the
value in
> that as an end in itself).
Agreed. Based on the latest hyperv V spec, I think only the following hypercalls
make sense for an enlightened guest:

1) HV_GET_PARTITION_ID
This is implemented in the patches I have submitted. This hypercall, currently
is not used by the currently shipping windows 2008 server.

2)  HV_GET_VP_REGISTERS/ HV_SET_VP_REGISTERS
I only have stub for these hypercalls (not implemented). Current windows 2008
server does not use these hypercalls.

3) HV_SWITCH_VA: I have implemented this hypercall.

4) HV_FLUSH_VA/HV_FLUSH_VA_LIST
I had implemented these hypercalls originally. In the current patch set, I have
stubbed out these hypercalls.

In addition to the hypercalls, Hyper V also surfaces functionality via synthetic
MSRs and CPUID leaves.
I have implemented all the relevant MSRs and CPUID leaves. 
>From a performance point of view, I think the MSR access to APIC registers
are the most important. As far as hypercalls go, the only one currently
implemented is the hypercall to change the page table base.  Some of the other
synthetic MSRs support features that the current windows 2008 server currently
is not using (timeouts for example).
Regards,

K. Y
  
>  --   Keir


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