Re: PV drivers for HVM guests

["Andrew D. Ball" <aball@us.ibm.com>]

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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