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

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Date:   Mon, 1 Nov 2021 09:34:08 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     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,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] [RFC] arm64: export this_cpu_has_cap

Hi Will

On 01/11/2021 09:01, Will Deacon wrote:
> 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.

As I understand correctly, this will now need to go via arm64 tree. The
CoreSight tree changes are pulled into Greg's tree and the next it will
happen is for the next release. Usually the fixes don't end up there
during the -rc cycles. So, I believe it is better if this goes via
arm64.

Suzuki