Re: KVM call minutes for Sept 21

[Joerg Roedel <joro@8bytes.org>]

On Sun, Sep 26, 2010 at 04:03:13PM +0200, Avi Kivity wrote:

> I don't expect drastic changes, but then, I still don't understand it well.
>
> Part of the review process is the maintainer becoming familiar (and, in  
> some cases, comfortable) with the code.  The nit-picking is often just  
> me proving to myself that I understand what's happening.

Right, understanding is an important part. One thing I try to achieve
for nested-svm is to make it less likely that unrelated code changes
break it. One step will be accessor funtions to change intercept masks
and tsc_offset.

> btw, speaking of drastic changes to nsvm, one thing I'd like to see is  
> the replacement of those kmaps with something like put_user_try() and  
> put_user_catch().  It should be as fast (or faster) than kmaps, and not  
> affect preemptibility.

Yes, I want to get rid of them too. I thought about using
copy_from/to_user in the vmrun/vmexit path. I need to measure if this
has any performance impact, though.
But the vmrun/vmexit path in nested-svm will see some major changes in
the near future anyway to improve performance and prepare it for
clean-bits emulation. In this step I will also address the kmap
problem. But first on the list for me is to make the instruction
emulator aware of instruction intercepts. Security is more important
then performance.

	Joerg