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Subject: Re: [Qemu-devel] [PATCH 4/7] target-i386: Dump illegal opcodes with
	-d unimp
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To: Paolo Bonzini <pbonzini@redhat.com>, =?UTF-8?Q?Herv=c3=a9_Poussineau?= <hpoussin@reactos.org>, qemu-devel@nongnu.org

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).


r~