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