Re: [Qemu-devel] [PATCH 4/7] target-i386: Dump illegal opcodes with -d unimp

[Paolo Bonzini]

On 03/03/2016 20:06, Richard Henderson wrote:
> On 03/03/2016 02:08 AM, Paolo Bonzini wrote:
>>> Do you want LOG_UNIMP or LOG_GUEST_ERROR?
>>
>> I would actually use LOG_IN_ASM.  As you noticed, guests sometimes use
>> illegal opcodes; another example is Xen's hypercall interface.
>>
>> On 03/03/2016 07:57, Hervé Poussineau wrote:
>>> This patch is not quiet on some operating systems:
>>> OS/2:
>>> ILLOPC: 000172e1: 0f a6
>>>
>>> Windows XP:
>>> ILLOPC: 00020d1a: c4 c4
>>>
>>> And very verbose in Windows 3.11, Windows 9x:
>>> ILLOPC: 000ffb17: 63
>>> ILLOPC: 000ffb17: 63
>>>
>>> Is it normal?
>>
>> Yes, it is.  As usual, Raymond Chen explains what's going on:
>>
>> https://blogs.msdn.microsoft.com/oldnewthing/20041215-00/?p=37003
> 
> Wow.  That's... interesting.
> 
> I think maybe I'll re-do the patch to distinguish between those opcodes
> that are completely unrecognized (which is what I was expecting to find)
> and those that raise #UD due to cpu state (e.g. this arpl in vm86 mode).

Good idea.  UD2 should not warn too, and also VEX prefixes outside
64-bit mode.

Any thoughts about patch 7?

Paolo