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

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

  - The function that allocates new nested p2ms probably needs an
    overhaul, as I said in my last email.


  - 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

In patch 1 the code that sends the IPIs was outside of the loop and moved into the loop.


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