Re: [Xen-devel] [PATCH] x86emul: simplify prefix handling for VMFUNC

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.09.16 at 11:52, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 05/09/16 10:13, Jan Beulich wrote:
>> LOCK prefixes get dealt with elsewhere and 66, F2, and F3 can all be
>> checked for in one go by looking at vex.pfx.
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> As far as subsuming the checks goes, this is fine.  However, is the code
> actually correct?  The manual makes no indication that the use of these
> prefixes is prohibited.

Hmm, indeed (and I probably should have checked). Looking at e.g.
XEND and XTEST (which is how I came here) I wonder though
whether the manual is wrong. Let's see if we can get this figured
out. Ravi, Paul: Said checks originate from commit a1b1572833
("VMX: add VMFUNC leaf 0 (EPTP switching) to emulator"). Can you
please clarify whether they got added in error, or whether you
have knowledge the SDM doesn't expose?

Thanks, Jan


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