Re: [PATCH 5/8] x86/head: remove useless zeroed word

H. Peter Anvin
2016-08-22T23:13:06Z

On August 22, 2016 3:47:48 PM PDT, Brian Gerst <brgerst@gmail.com> wrote:
>On Mon, Aug 22, 2016 at 6:23 PM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On August 22, 2016 2:48:46 PM PDT, Andi Kleen <andi@firstfloor.org>
>wrote:
>>>Josh Poimboeuf <jpoimboe@redhat.com> writes:
>>>
>>>> This zeroed word has no apparent purpose, so remove it.
>>>>
>>>> Brian Gerst says:
>>>>
>>>> "FYI the word used to be the SS segment selector for the LSS
>>>> instruction, which isn't needed in 64-bit mode."
>>>>
>>>
>>>Seems dangerous. It wouldn't surprise me if some CPUs or x86
>emulations
>>>load it anyways and trigger page faults if there is really nothing
>>>there.
>>>
>>>-Andi
>>
>> Yes, seems pointlessly risky.
>
>It was added in commit 9cf4f298e29abba25c16679fe7be70898223167e,
>copied from 32-bit but never used. It doesn't look like we ever used
>LSS on 64-bit.
>
>--
>Brian Gerst

Ah, ok. Wasn't in front of a computer.
--
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