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Re: [PATCH v2 1/3] x86/retpoline: rename retpoline Kconfig check to include GCC prefix
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Thu, 17 Feb 2022 11:37:53 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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On Thu, Feb 17, 2022 at 10:04:01AM +0100, Jan Beulich wrote:
> On 17.02.2022 09:59, Jan Beulich wrote:
> > On 16.02.2022 17:21, Roger Pau Monne wrote:
> >> Current retpoline checks apply to GCC only, so make it obvious by
> >> prefixing the Kconfig option with GCC. Keep the previous option as a
> >> way to signal generic retpoline support regardless of the underlying
> >> compiler.
> >>
> >> No functional change intended.
> >>
> >> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> >> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> ---
> >> Changes since v1:
> >> - Put def_bool before depend on.
> >
> > Just for the record: A slightly shorter alternative would have been ...
> >
> >> --- a/xen/arch/x86/Kconfig
> >> +++ b/xen/arch/x86/Kconfig
> >> @@ -32,9 +32,13 @@ config ARCH_DEFCONFIG
> >> string
> >> default "arch/x86/configs/x86_64_defconfig"
> >>
> >> -config INDIRECT_THUNK
> >> +config GCC_INDIRECT_THUNK
> >> def_bool $(cc-option,-mindirect-branch-register)
> >>
> >> +config INDIRECT_THUNK
> >> + def_bool y
> >> + depends on GCC_INDIRECT_THUNK
> >
> > config INDIRECT_THUNK
> > bool
> >
> > config GCC_INDIRECT_THUNK
> > def_bool $(cc-option,-mindirect-branch-register)
> > select INDIRECT_THUNK
>
> Oh, looking at patch 3 again (which I should have still had in mind)
> this would of course not help. Yet ..
>
> > A more appropriate thing to use for "depends on" might have been
> > CC_IS_GCC. With the next patch in mind this would then avoid
> > potential confusion if e.g. Clang folks decided to (also) support
> > the gcc style command line options.
>
> ... adding this dependency (and a respective one in patch 2) might
> still be a good thing.
So you would like to make GCC_INDIRECT_THUNK depend on CC_IS_GCC?
That would be fine, but I think it's extremely unlikely for CLANG to
adopt the GCC options - I've already mentioned at implementation time
and they refused.
Thanks, Roger.
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