Xen devel - Oct 2008 - exception handler caused by context switching and setting trap flag

hello:
      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?
 Thanks.
 JianLi

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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@163.com> wrote:
>
>  hello:
>       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?
>  Thanks.
>  JianLi
>

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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@163.com>
>  Thank you very very very much!!!
>
>
>
>
> 在2008-10-29，"Paul Samon" <paul.samon@gmail.com> 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@163.com>
>
>>  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@gmail.com> 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@163.com>
>>
>>>  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?
>>>  Thanks.
>>>  JianLi.
>>>
>>>
>>>
>>> 在2008-10-29，"Paul Samon" <paul.samon@gmail.com> 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@163.com>
wrote:
>>>
>>>>
>>>>  hello:
>>>>       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?
>>>>  Thanks.
>>>>  JianLi
>>>>
>>>

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