Re: [PATCH] x86/speculation: Use AMD specific retpoline for inline asm on AMD

[Zhenzhong Duan]

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