Re: [PATCH v10 2/9] x86emul: rework CMP and TEST emulation

[Jan Beulich <jbeulich@xxxxxxxx>]

On 29.05.2020 14:24, Andrew Cooper wrote:
> On 25/05/2020 15:26, Jan Beulich wrote:
>> Unlike similarly encoded insns these don't write their memory operands,
> 
> "write to their".
> 
>> and hence x86_is_mem_write() should return false for them. However,
>> rather than adding special logic there, rework how their emulation gets
>> done, by making decoding attributes properly describe the r/o nature of
>> their memory operands.
> 
> Describe how?  I see you've change the order of operands encoding, but
> then override it back?

There's no overriding back, I don't think: I change the table entries
for opcodes 0x38 and 0x39, with no other adjustments the the attributes
later on. For the other opcodes I leave the table entries as they are,
and override the attributes for the specific sub-cases (identified by
ModRM.reg).

For opcodes 0x38 and 0x39 the change of the table entries implies
changing the order of operands as passed to emulate_2op_SrcV(), hence
the splitting of the cases in the main switch().

I didn't think this was necessary to spell out in the commit message,
but of course I can re-use most of the text above and add it into
there, if you think that would help.

Jan