Re: [Xen-devel] [PATCH 0 of 5] v2: Nested-p2m cleanups and locking changes

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On 06/27/11 15:20, Tim Deegan wrote:
> At 14:15 +0100 on 27 Jun (1309184128), Tim Deegan wrote:
> > At 14:23 +0200 on 27 Jun (1309184586), Christoph Egger wrote:
> > > >   - Why is there a 10x increase in IPIs after this series?  I don't see
> > > >     what sequence of events sets the relevant cpumask bits to make this
> > > >     happen.
> > > In patch 1 the code that sends the IPIs was outside of the loop and
> > > moved into the loop.
> > Well, yes, but I don't see what that causes 10x IPIs, unless the vcpus
> > are burning through np2m tables very quickly indeed.  Maybe removing the
> > extra flushes for TLB control will do the trick.  I'll make a patch...
> Hmmm, on second thoughts, we can't remove those flushes after all.
> The np2m is in sync with the p2m but not with the guest-supplied p2m,
> so we do need to flush it when the guest asks for that to happen.
Right. I thought on that when I developped the code but then I forgot.
We should add a comment.

Christoph


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