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Re: [Xen-devel] [PATCH RFC] x86emul: unconditionally deliver #UD for LWP insns
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <JBeulich@xxxxxxxx>
- Date: Wed, 17 Jul 2019 13:07:04 +0000
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- Cc: Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Wed, 17 Jul 2019 13:07:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH RFC] x86emul: unconditionally deliver #UD for LWP insns
On 17.07.2019 13:42, Andrew Cooper wrote:
> On 17/07/2019 07:42, Jan Beulich wrote:
>> This is to accompany commit ("x86/svm: Drop support for AMD's
>
> 91f86f8634
Hmm, odd - I'm sure I had checked, resulting in the impression that
this didn't get committed yet.
>> Lightweight Profiling").
>>
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>
>> ---
>> With AMD apparently having abandoned XOP encoded insns, another option
>> would seem to be to simply wire all unrecognized ones into #UD (rather
>> then returning UNIMPLEMENTED/UNRECOGNIZED).
>
> There are still some XOP instructions which actually work on Fam17h
> processors, if you ignore CPUID and go blindly executing.
>
> Given no official statement that XOP is dead, I'd keep the support we
> currently have.
Then my remark wasn't clear enough: I'm not suggesting to rip out
XOP insn support we have. I'm instead considering whether to wire
all unsupported XOP encodings into #UD (rather than return
UNIMPLEMENTED/UNRECOGNIZED for them), not just the LWP ones.
Jan
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