Re: [PATCH v8 02/12] x86emul: support MOVDIR{I,64B} insns

[Jan Beulich <jbeulich@xxxxxxxx>]

On 07.05.2020 20:30, Andrew Cooper wrote:
> On 05/05/2020 09:13, Jan Beulich wrote:
>> Introduce a new blk() hook, paralleling the rmw() one in a certain way,
>> but being intended for larger data sizes, and hence its HVM intermediate
>> handling function doesn't fall back to splitting the operation if the
>> requested virtual address can't be mapped.
>>
>> Note that SDM revision 071 doesn't specify exception behavior for
>> ModRM.mod == 0b11; assuming #UD here.
> 
> Still stale?  It does #UD on current hardware, and will cease to #UD in
> the future when the encoding space gets used for something else.

What do you mean by "still stale"? Other insns allowing for only
memory operands have the #UD spelled out in the doc. Are you
implying by the 2nd sentence that it should rather be
"goto unrecognized_insn"? I'm afraid we're not very consistent
yet with what we do in such cases; I could certainly work
towards improving this, but the question is whether it is really
sensible in all cases to assume such partially unused encodings
may get used in the future.

>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Reviewed-by: Paul Durrant <paul@xxxxxxx>
> 
> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Thanks, but as per my reply to your patch 6 comment the patch
here will need to be revised, so I'll not apply this just yet
unless you indicate up front that you're fine with me keeping it.

Jan