linux-kernel - Re: [PATCH] [RFC] arm64: export this_cpu_has

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Date:   Mon, 1 Nov 2021 09:01:44 +0000
From:   Will Deacon <will@...nel.org>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Suzuki K Poulose <suzuki.poulose@....com>,
        Arnd Bergmann <arnd@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Arnd Bergmann <arnd@...db.de>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        David Brazdil <dbrazdil@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [RFC] arm64: export this_cpu_has_cap

On Fri, Oct 29, 2021 at 07:06:23PM +0100, Catalin Marinas wrote:
> On Fri, Oct 29, 2021 at 02:31:23PM +0100, Suzuki K Poulose wrote:
> > On 29/10/2021 12:30, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@...db.de>
> > > 
> > > It's now used in a coresight driver that can be a loadable module:
> > > 
> > > ERROR: modpost: "this_cpu_has_cap" [drivers/hwtracing/coresight/coresight-trbe.ko] undefined!
> > > 
> > > Fixes: 8a1065127d95 ("coresight: trbe: Add infrastructure for Errata handling")
> > 
> > Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> > Tested-by: Suzuki K Poulose <suzuki.poulose@....com>
> > 
> > Will, Catalin, Mathieu,
> > 
> > Do you have a preference on how this fix can be pulled in ? This may
> > be safe to go via coresight tree if it is not too late. Otherwise,
> > it could go via the arm64 tree.
> 
> I think Will already closed/tagged the arm64 tree for the upcoming
> merging window, though he could take it as a fix afterwards.
> 
> If it doesn't conflict with the arm64 for-next/core, it's fine by me to
> go through the coresight tree.
> 
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > > ---
> > > Not sure if we actually want this to be exported, this is my local
> > > workaround for the randconfig build bot.
> > > ---
> > >   arch/arm64/kernel/cpufeature.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > > 
> > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> > > index ecbdff795f5e..beccbcfa7391 100644
> > > --- a/arch/arm64/kernel/cpufeature.c
> > > +++ b/arch/arm64/kernel/cpufeature.c
> > > @@ -2864,6 +2864,7 @@ bool this_cpu_has_cap(unsigned int n)
> > >   	return false;
> > >   }
> > > +EXPORT_SYMBOL(this_cpu_has_cap);
> 
> EXPORT_SYMBOL_GPL? I think this_cpu_has_cap() is a bit more more
> specialised than cpus_have_const_cap().
> 
> With that:
> 
> Acked-by: Catalin Marinas <catalin.marinas@....com>

Yes, at this stage I think it's best for this to go via the Coresight tree.
So with the _GPL export:

Acked-by: Will Deacon <will@...nel.org>

If that doesn't work for some reason, I can take it next week after the
initial arm64 queue has been merged. Please just let me know.

Will