Re: [Xen-devel] [PATCH 02/17] x86emul: fetch all insn bytes during the decode phase

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.09.16 at 16:48, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 14/09/16 10:55, Jan Beulich wrote:
>>>>> On 13.09.16 at 20:44, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> I would suggest leaving the generate_exception_if(mode_64bit(), EXC_UD,
>>> -1); after the ASSERT() so even if we do end up in a wonky state, we
>>> don't try to jump the guest to 0.
>> That would look really strange to a reader, I think, and hence I'd
>> rather not do this if I can get the patch accepted without.
> 
> It is conceptually no different to
> 
> default:
> ASSERT_UNREACHABLE();
> return;

Except that
- we don't always follow ASSERT_UNREACHABLE() with return (or
  whatever else),
- here we don't risk doing ourselves or the guest anything bad: We'll
  just produce undefined behavior, which is to be expected if we are
  in a "wonky state".

If leaving the exception generation in is the only way to get this
ack-ed, I'll do so, but I'd prefer if I wasn't required to.

Jan


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