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[Xen-devel] vmx_update_guest_cr() losing EXCEPTION_BITMAP setting


  • To: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Byrne, John (HP Labs)" <john.l.byrne@xxxxxx>
  • Date: Mon, 11 May 2009 04:32:11 +0000
  • Accept-language: en-US
  • Acceptlanguage: en-US
  • Delivery-date: Sun, 10 May 2009 21:33:47 -0700
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcnR8XOAYOeTv7J5Qqms8GGZVbPMcQ==
  • Thread-topic: vmx_update_guest_cr() losing EXCEPTION_BITMAP setting

Running a heavily modified xen-unstable changset 19590:f80cf52a4fb6 with 
debugger_attached set, I was seeing the debug traps getting lost from the 
EXCEPTION_BITMAP in vmx_update_guest_cr() when transitioning from real to 
protected mode.  In my codebase, I could fix this trivially by clearing the 
debug_state_latch and letting vmx_do_resume() reapply the setting. However, 
while it looks like a valid issue in the unmodified codebase, I'm not sure. So 
maybe someone might test/examine it and decide if it is real and whether some 
more complex fix is required?

John Byrne


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