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Re: [Xen-devel] [PATCH 14/14] Nested Virtualization: hap-on-hap

To: Christoph Egger <Christoph.Egger@xxxxxxx>
Subject: Re: [Xen-devel] [PATCH 14/14] Nested Virtualization: hap-on-hap
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Mon, 9 Aug 2010 14:18:22 +0100
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This looks a lot nicer than the last version I reviewed.  I'm still
concerned about TLB and p2m flushes, though.

- I can't see how writes to the 'host' p2m table cause the 'shadow' p2m
  tables to be flushed.  I might just have missed it. 
- The p2m_flush operations don't look safe against other vpcus.  Mostly
  they're called with v==current, which looks OK, but what if two vcpus
  are running on the same p2m?  Also when p2m_get_nestedp2m() flushes
  the domain's LRU p2m, there's no shootdown if that p2m is in use on
  another pcpu.  That could happen if the VM has more vcpus than
  MAX_NESTEDP2M.  (Actually, that case is probably pretty broken



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

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