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RE: [Xen-ia64-devel] RE: [PATCH] Patch to make latest hg multi-domainback to work


  • To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Byrne, John (HP Labs)" <john.l.byrne@xxxxxx>
  • From: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
  • Date: Thu, 8 Sep 2005 19:34:28 -0700
  • Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Fri, 09 Sep 2005 02:32:49 +0000
  • List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
  • Thread-index: AcWvySFLppJ+ILkHRKOQH/MX6thvfgEH6v3wABtDOHAAAcMDgAAeqRQAAAEH+PAAAsa6oA==
  • Thread-topic: [Xen-ia64-devel] RE: [PATCH] Patch to make latest hg multi-domainback to work

> Since vcpu_itc_no_srlz is always invoked after 
> translate_domain_pte which will force _PAGE_PL_2 on, it seems 
> unlikely to insert a machine TC entry with incorrect 
> privilege level. After some search for reference to 
> dtlb/dtlb_pte, I found hyper_ptc_ga though not the full 
> reason, but possible a problematic point? In that section of 
> code, only vcpu->arch.dtlb/itlb is marked as non-present by:
> 
> adds r25=IA64_VCPU_DTLB_OFFSET,r27
> adds r26=IA64_VCPU_ITLB_OFFSET,r27;;
> ...
> st8 [r25]=r24                 // set 1-entry i/dtlb as not present
> 
> Instead vcpu->arch.dtlb_pte is not touched. So after my patch 
> changed match_dtlb to return guest pte, above problematic 
> code may leave them out of sync there. Comments?

I agree this is a bug, but I'm not sure it explains
the problem.  I will turn off HYPER_PTC_GA and see
if the problem goes away.

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