Re: [Xen-devel] PV drivers for HVM guests

["Ky Srinivasan" <ksrinivasan@xxxxxxxxxx>]

Agreed.

K. Y

>>> On Thu, Oct 5, 2006 at 10:59 AM, in message <45251DEB.1070708@xxxxxxxxxx>,
"Andrew D. Ball" <aball@xxxxxxxxxx> wrote: 
> Agreed.  What I meant is that it would be nice if the device model
> were modified to have better performance for things like OS/2, where
> writing paravirtual drivers would be less emphasized.
> 
> Peace.
> Andrew
> 
> Ky Srinivasan wrote:
>> Andrew,
>> 
>> The I/O performance of HVM guests with PV drivers is SIGNIFICANTLY better 
> than what we get without PV drivers. I will post the patches after some 
> additional testing and code cleanup.
>> 
>> Regards,
>> 
>> K. Y
>> 
>> 
>>>>>On Tue, Oct 3, 2006 at  6:19 PM, in message
>> 
>> <1159913996.27206.37.camel@localhost>, "Andrew D. Ball" <aball@xxxxxxxxxx>
>> wrote: 
>> 
>>>Interesting!  Ideally, there would be better performance in the base HVM
>>>device model.  I think I know of some people that are working hard on
>>>that.
>>>
>>>I'm curious to see what you've done for (1) and (2).
>>>
>>>Peace.
>>>Andrew
>>>
>>>On Tue, 2006-   10-   03 at 16:31 -   0400, Ky Srinivasan wrote:
>>>
>>>>I am trying to build PV drivers for SLES9 HVM guests. SLES 9 is based on 
>>>>the 
>>>
>>>2.6.5 kernel. Since the PV driver code is really designed for the latest 
>>>kernel release, I have had many issues/problems in building the PV drivers 
>>>for older Linux OS targets -    I have only been looking at the issues with 
> 2.6.5 
>>>kernel base and I suspect the problem will be even worse if one were to look 
>>>at older Linux kernels. This is unfortunate since PV drivers are so critical 
>>>for HVM guests and there is considerable interest in supporting legacy Linux 
>>>environments as HVM guests. The problems I have had to deal with can be 
>>>broadly classified into:
>>>
>>>>a) Compiler related issues
>>>>b) Missing functionality in the legacy kernel -    this includes features 
>>>>as 
>>>
>>>well as changed data structures
>>>
>>>>c) Implementation differences of a given feature
>>>>
>>>>These differences can be dealt with in a couple of different ways:
>>>>1) Modify the code in the PV drivers under appropriate compilation switches 
>>>
>>>to deal with the differences in the base kernels.
>>>
>>>>2)  Introduce  a compatibility component that bridges the gap between the 
>>>
>>>current PV code and a given Linux target and leave much of the PV driver  
>>>code untouched.
>>>
>>>>I have implemented both these schemes for the sles9 kernel and would like 
>>>>to 
>>>
>>>get your input on your preference. I personally like option 2. Going 
>>>forward, 
> 
>>>the evolution of PV drivers needs to be constrained by the required support 
>>>for legacy Linux environments. 
>>>
>>>>Regards,
>>>>
>>>>K. Y. Srinivasan 
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>
>>>
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>> 
>> 
>> 
>> 
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