Re: [Xen-devel] [PATCH 3/8] x86emul: support BMI1 insns

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.01.17 at 14:51, <andrew.cooper3@xxxxxxxxxx> wrote:
> Right.  What happens in reality is this:
> 
> --- Xen Test Framework ---
> Environment: HVM 32bit (No paging)
> Test VEX.W matching mode:
>   andn cccca5a5, ff00ff00 = 00cc00a5
> Test VEX.W opposite to mode:
>   andn cccca5a5, ff00ff00 = 00cc00a5
> Test result: SUCCESS
> 
> --- Xen Test Framework ---
> Environment: HVM 64bit (Long mode 4 levels)
> Test VEX.W matching mode:
>   andn cccca5a5cccca5a5, ff00ff00ff00ff00 = 00cc00a500cc00a5
> Test VEX.W opposite to mode:
>   andn cccca5a5cccca5a5, ff00ff00ff00ff00 = 0000000000cc00a5
> Test result: SUCCESS
> 
> So VEX.W is ignored in 32bit (i.e. doesn't raise #UD), and *does* cause
> 64bit mode to operate on 32bit operands, contrary to the manual.

Doesn't look so to me: The first result is a 64-bit one, and I'd expect
VEX.W=1 to be "matching mode".

Jan


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