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

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On 06/27/11 12:56, Tim Deegan wrote:
> At 11:46 +0100 on 27 Jun (1309175170), Tim Deegan wrote:
> > This patch series tidies up a few bits ofthe nested p2m code.
> > The main thing it does is reorganize the locking so that most of the
> > changes to nested p2m tables happen only under the p2m lock, and the
> > nestedp2m lock is only needed to reassign p2m tables to new cr3 values.
> There are still a few things I'm not convinced about in the nested NPT
> code:
>
>   - The function that allocates new nested p2ms probably needs an
>     overhaul, as I said in my last email.
Ack.

>   - The flushing policy is a bit confusing: e.g., what exactly ought to
>     happen when the guest sets the tlb-control bits?  AFAICS the nested-p2ms
>     are already kept in sync with host-p2m changes, and we flush all
>     TLBs when we update nested-p2ms, so can we skip this extra flush?
Yes, we can.

>   - 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.
Christoph


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