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RE: [Xen-devel] [PATCH] This patch fixes several issues related to vmxassist

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
  • From: "Li, Xin B" <xin.b.li@xxxxxxxxx>
  • Date: Fri, 31 Mar 2006 19:06:08 +0800
  • Cc: Xen Devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Fri, 31 Mar 2006 11:07:49 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcZUqC5wVY7W+52IToqb9lbzaT+Y7wACczUA
  • Thread-topic: [Xen-devel] [PATCH] This patch fixes several issues related to vmxassist

>In fact, the existing implementation of address() is kludgy. 
>It already 
>does tests on the selector value to decide whether it is likely to 
>refer to a protected-mode or real-mode segment. Unfortunately the test 
>may sometimes yield false positives (selectors that look like they 
>could be a valid protected-mode value, but actually it's some 
>real-mode selector).
>I don't know the heritage of that code. I expect someone 
>decided it was 
>good enough to be getting on with but maybe now it is time to revisit 
>and see if we can implement a watertight version which correctly uses 
>hidden segment descriptor state which is readily available 
>when running 
>on VMX.

My patch just enhanced the current implementation, and actually it
breaks windows, but I have a updated version in hand, and tests show
that all the combinations is OK till now.

In my mind, the correct way is to identify whether a cpu is in big real
mode, but seems this is a little bit hard to do.

>It might be worth pinging Leendert about this and see what he thinks.

Yes, we have contact with him :-)


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