Re: [Xen-devel] [PATCH 04/17] x86emul: complete decoding of two-byte instructions

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 26/09/16 08:34, Jan Beulich wrote:
>
>> 0F6F was previously ImplicitOps|ModRM, but looks like it should be ModRM 
>> like the rest of 0F6x.  0F7F, 0FC7 and 0FE7 similarly.
> Why? As mentioned elsewhere I think the (otherwise benign)
> ImplicitOps (as well as the individual DstImplicit and SrcImplicit)
> serve as documentation: Opcodes we actually handle have them
> specified, whereas opcodes getting decoded but not emulated
> don't. See the MOVQ and MOVD patches in the other series, which
> add ImplicitOps to the table entries they add emulation for.

By that argument, any instruction we have an emulation for should gain
ImplicitOps.

As it has the value 0, I only find that it further confuses an already
complicated piece of logic, as reading the decode gives the false
impression that something is different.

~Andrew

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