Re: [Xen-devel] VMX check_for_null_selector()

[Keir Fraser <keir@xxxxxxxxxxxxx>]

Good question, it's something I've been meaning to ask the Intel guys
about...

 K.

On 22/11/06 08:46, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

> What is the hidden background for using this function when the guest
> is in protected mode? When the selector used is a null one (and not
> in 64-bit mode), the instruction should not cause an
> EXIT_REASON_IO_INSTRUCTION exit at all, but rather should cause
> a GP fault in the guest. In 64-bit mode, a null selector isn't invalid,
> and hence doesn't need checking for.
> What I'm trying to determine is whether the function must be fixed
> (to deal with (a) non-zero CS base addresses and (b) the fact that
> on INS there shouldn't be checking for segment overrides, but ES
> should be used in all cases) or can be removed.
> 
> Thanks, Jan
> 
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