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SubjectRe: [PATCH] x86/speculation: Use AMD specific retpoline for inline asm on AMD
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On 2018/9/18 21:00, Peter Zijlstra wrote:
> On Tue, Sep 18, 2018 at 08:04:44PM +0800, Zhenzhong Duan wrote:
>> On 2018/9/18 18:59, Peter Zijlstra wrote:
>>> On Tue, Sep 18, 2018 at 06:31:07PM +0800, Zhenzhong Duan wrote:
>>>> On 2018/9/18 17:50, Peter Zijlstra wrote:
>>>>> On Mon, Sep 17, 2018 at 10:17:30PM -0700, Zhenzhong Duan wrote:
>>>>>> -#elif defined(CONFIG_X86_32) && defined(CONFIG_RETPOLINE)
>>>>>> +#elif defined(CONFIG_RETPOLINE)
>>>>> This doesn't make any sense..
>>>> This change is used for x86_64 to have minimal Retpoline support when
>>>> CONFIG_RETPOLINE is defined but RETPOLINE isn't defined, or I missed
>>>> something?
>>> No it doesn't.
>>>
>>> #if defined(X86_64) && defined(RETPOLINE)
>>>
>>> /* x86_64 retpoline goes here */
>>>
>>> #elif defined(RETPOLINE)
>>>
>>> /* !x86_64 retpoline goes here */
>>>
>>> #else
>>>
>>> /* !retpoline goes here
>>>
>>> #endif
>> Sorry, but I am confused.
>> So where is 'if defined(x86_64) && !defined(RETPOLINE) &&
>> defined(CONFIG_RETPOLINE)' go?
> Argh, CONFIG_RETPOLINE vs RETPOLINE :/
>
> The thing is, the one you modify has a comment on that explains why it
> is i386 only. CET and retpolines don't like one another much.
>
> And the x86_64 version uses %V which requires new GCC.
>
> So I'm all for fixing the RETPOLINE_AMD thing, but at this point nobody
> should use the minimal stuff, that's just delusional.
>

Clear, thanks for your explanation.

Zhenzhong

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