Re: [Xen-devel] Interrupt issues with hvm_emulate_one_vm_event()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.05.17 at 16:37, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 05/26/17 17:29, Jan Beulich wrote:
>>>>> On 25.05.17 at 11:40, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>> I've noticed that, with pages marked NX and vm_event emulation, we can
>>> end up emulating an ud2, for which hvm_emulate_one() returns
>>> X86EMUL_EXCEPTION in hvm_emulate_one_vm_event().
>> 
>> Could you explain what would lead to emulation of UD2?
> 
> If you mean in which cases does our engine mark pages NX, I'll have to
> ask and get back to you. If you mean why generally would an UD2 end up
> being the instruction where RIP causes an execute violation fault, I'll
> have to check.

The question was more for the latter, as I don't understand what
good could come from executing UD2 intentionally, unless the
entity doing so knows there is an emulator around to do something
sensible with it.

Jan


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