Xen devel - Jan 2006 - Page fault in VT-x and shadow fault/inject exception (xen 3.0)

Hello,

I am trying to understand the code of Vt-x (starting with vmx.c)

I would be grateful if someone can calrify some issue
which puzzles me regarding vmx_do_page_fault() method in
xen/arch/x86/vmx.c. (xen 3.0).

This method is called when there is a page fault (and
when certain conditions regarding bit 14 of the exception bitamp are met)
and it is called upon a VMEXIT in a handler.(vmx_vmexit_handler()).

The vmx_do_page_fault() calls shadow_fault() ;
if shadow_fault() fails (retruning 0) than we call
vmx_inject_exception().

My question is : why do we need to call shadow_fault() at
the first place ? is it some kind of cache ?
It seems to me that in non-vmx environment we don''t call
shadow_fault() but I am not sure about it.
And what, in short, does vmx_inject_exception() do ?

Regards,
MR

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