Xen devel - Mar 2012 - Quick Questions about page fault?

Hi everyone,
         I want to know more about page fault. How does Xen handle
page fault in both PV and HVM?
         Which function will Xen call?   What is the difference?
         I assume that Xen will notify Guest OS about the page fault
only when it needs to?
         But I change the do_page_fault（） and remove the some pages'
_PAGE_RW.
         I also add some code to restore the _PAGE_RW in the
do_page_fault. If the error_code is 0, do_page_fault returen?
         But I get some error somehow?
         Can anyone tell me more about Xen's page fault routine? Thank
U for answering.
R

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At 08:11 +0800 on 03 Mar (1330762314), R wrote:
> Hi everyone,
>          I want to know more about page fault. How does Xen handle
> page fault in both PV and HVM?
>          Which function will Xen call?   What is the difference?
PV: do_page_fault()
HVM with shadow pagetables: sh_page_fault() (via paging_fault())
HVM with HAP does not intercept pagefaults in the hypervisor. 
>          I assume that Xen will notify Guest OS about the page fault
> only when it needs to?
Of course. 
>          But I change the do_page_fault???? and remove the some
pages'' _PAGE_RW.
>          I also add some code to restore the _PAGE_RW in the
> do_page_fault. If the error_code is 0, do_page_fault returen?
>          But I get some error somehow?
I''m afraid your description is too vague for anyone to understand what
the problem is.
Please read http://wiki.xen.org/wiki/AskingXenDevelQuestions before
posting again.

Tim.