On Wed, 2011-01-26 at 17:17 +0200, Avi Kivity wrote:
> On 01/26/2011 02:20 PM, Glauber Costa wrote:
> > On Wed, 2011-01-26 at 13:13 +0200, Avi Kivity wrote:
> > > On 01/24/2011 08:06 PM, Glauber Costa wrote:
> > > > As a proof of concept to KVM - Kernel Virtual Memory, this patch
> > > > implements wallclock grabbing on top of it. At first, it may seem
> > > > as a waste of work to just redo it, since it is working well. But over the
> > > > time, other MSRs were added - think ASYNC_PF - and more will probably come.
> > > > After this patch, we won't need to ever add another virtual MSR to KVM.
> > > >
> > >
> > > So instead of adding MSRs, we're adding area identifiers. What did we gain?
> > * No risk of namespace clashes of any kind,
> > * less need for userspace coordination for feature enablement,
> That's a bug, not a feature.
I don't see why.
I's about feature enablement, not feature discovery.
> > * size information goes together with base, allowing for extending
> > structures (well, maybe I should add versioning explicitly?)
> We could do that as well with wrmsr, by having the size as the first
> field of the structure. Usually the size isn't really interesting,
> though, since you need to discover/enable the new features independently.
Which structure? For msrs, we're usually going for just an u64, but of
course we could change that when needed.