Re: no definition of virtualization exception in exception table

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 28/04/16 09:53, George Dunlap wrote:
> On Thu, Apr 28, 2016 at 3:37 AM, Big Strong <fangtuo90@gmail.com> wrote:
>> There is a #VE exception defined in p2086 of Intel Software Development
>> Manual, however, no definition of exception handler is availble in Xen 4.6.
>> Should I define the handler by myself by modifying the source code of xen,
>> or is there a way to define the handler of the reserved IDT vectors (0-31,
>> #VE is 20) without modifying the source code?
> What are you actually trying to do?
>
> Xen shouldn't be generating #VEs itself, so it doesn't need a #VE
> handler.  Those should only be generated by guests in HVM mode (if I'm
> remembering things correctly).  In those cases the #VE will either be
> delivered directly to the guest, or it will cause a VMEXIT.

Correct.  #VE occurs from a EPT permission violation when appropriate
controls are set up, and are either become a VMEXIT or an in-guest #VE
depending on the .surpress_ve bit in a leaf epte.

Unless you are nesting Xen inside another hypervisor on Intel hardware,
and have opted in to receiving #VE's, you won't encounter any.

~Andrew

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