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Re: Re: Re: Re: [Xen-devel] exception handler caused by context switching and setting trap flag

  • To: lijiandm <lijiandm@xxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: "Paul Samon" <paul.samon@xxxxxxxxx>
  • Date: Wed, 29 Oct 2008 11:27:02 +0800
  • Cc:
  • Delivery-date: Tue, 28 Oct 2008 20:27:24 -0700
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You're welcome. BTW, in the case of EPT/NPT, HVM guest's writng to CR3 would not incur VMexit or something.
-- Paul S.
2008/10/29 lijiandm <lijiandm@xxxxxxx>
 Thank you very very very much!!!

在2008-10-29,"Paul Samon" <paul.samon@xxxxxxxxx> 写道:
(Here we don't consider EPT)
When HVM guest (for Intel, namely VMX guest) tried to write_to_cr3, a VMexit will occur (search for EXIT_REASON_CR_ACCESS in Xen code)

2008/10/29 lijiandm <lijiandm@xxxxxxx>
 Yes,I mean change the context in CR3,process switched in and out by OS.
 In another word,I want to capture the behavior caused by the MOV to CR3.

 Thanks,wait for your reply.

在2008-10-29,"Paul Samon" <paul.samon@xxxxxxxxx> 写道:

> the exception handler used to handle the context switch in HVM guest
What context switch? process context switch?
On Xen, the process context switch inside HVM guest functions in exactly the same way as it does on bare metal.

2008/10/29 lijiandm <lijiandm@xxxxxxx>
 Yes, I use an Intel VT-capable host.
 But my problem is I want to find out the exception handler used to handle the context switch in HVM guest.Is there such a exception handler? And if I want to replace it ,what should I do?

在2008-10-29,"Paul Samon" <paul.samon@xxxxxxxxx> 写道:

HVM guest's VMexit is handled by Xen itself (see xen/arch/x86/hvm/vmx/entry.S: vmx_asm_vmexit_handler if you're using an Intel VT-capable host) , not Dom0 (a PV guest) at all.
vcpu context switch itself doesn't cause VMexit.
-- Paul S.

On Wed, Oct 29, 2008 at 9:32 AM, lijiandm <lijiandm@xxxxxxx> wrote:
      I have two trivial question.
      In dom0,which exception handler is used to handle VMexit caused by context switching in domU?
      If I want to replace the handler ,what should I do?

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