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

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.


Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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