On Sun, Aug 25, 2013 at 09:26:47PM -0400, Chris Metcalf wrote:
> On 8/25/2013 7:39 AM, Gleb Natapov wrote:
> > On Mon, Aug 12, 2013 at 04:24:11PM -0400, Chris Metcalf wrote:
> >> This change provides the initial framework support for KVM on tilegx.
> >> Basic virtual disk and networking is supported.
> >>
> > This needs to be broken down to more reviewable patches.
>
> I already broke out one pre-requisite patch that wasn't strictly KVM-related:
>
> https://lkml.org/lkml/2013/8/12/339
>
> In addition, we've separately arranged to support booting our kernels in a
> way that is compatible with the Tilera booter running at the highest
> privilege level, which enables multiple kernel privilege levels:
>
> https://lkml.org/lkml/2013/5/2/468
>
> How would you recommend further breaking down this patch? It's pretty much
> just the basic support for minimal KVM. I suppose I could break out all the
> I/O related stuff into a separate patch, though it wouldn't amount to much;
> perhaps the console could also be broken out separately. Any other
> suggestions?
>
First of all please break out host and guest bits. Also I/O related stuff,
like you suggest (so that guest PV bits will be in separate patch) and
change to a common code (not much as far as I see) with explanation why
it is needed. (Why kvm_vcpu_kick() is not needed for instance?)
> > Also can you
> > describe the implementation a little bit? Does tile arch has vitalization
> > extension this implementation uses, or is it trap and emulate approach?
> > If later does it run unmodified guest kernels? What userspace are you
> > using with this implementation?
>
> We could do full virtualization via trap and emulate, but we've elected to do
> a para-virtualized approach. Userspace runs at PL (privilege level) 0, the
> guest kernel runs at PL1, and the host runs at PL2. We have available per-PL
> resources for various things, and take advantage of having two on-chip timers
> (for example) to handle timing for the host and guest kernels. We run the
> same userspace with either the host or the guest.
>
OK, thanks for explanation. Why have you decided to do PV over trap and
emulate?
--
Gleb.
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