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Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as
 EXPORT_SYMBOL_GPL
To:     Mike Rapoport <rppt@linux.ibm.com>,
        Michal Hocko <mhocko@kernel.org>
Cc:     Jia He <justin.he@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Baoquan He <bhe@redhat.com>,
        Chuhong Yuan <hslester96@gmail.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, linux-nvdimm@lists.01.org,
        Kaly Xin <Kaly.Xin@arm.com>
References: <20200707055917.143653-1-justin.he@arm.com>
 <20200707055917.143653-2-justin.he@arm.com>
 <20200707115454.GN5913@dhcp22.suse.cz> <20200707121302.GB9411@linux.ibm.com>
From:   David Hildenbrand <david@redhat.com>
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Organization: Red Hat GmbH
Message-ID: <474f93e7-c709-1a13-5418-29f1777f614c@redhat.com>
Date:   Tue, 7 Jul 2020 14:26:08 +0200
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On 07.07.20 14:13, Mike Rapoport wrote:
> On Tue, Jul 07, 2020 at 01:54:54PM +0200, Michal Hocko wrote:
>> On Tue 07-07-20 13:59:15, Jia He wrote:
>>> This exports memory_add_physaddr_to_nid() for module driver to use.
>>>
>>> memory_add_physaddr_to_nid() is a fallback option to get the nid in case
>>> NUMA_NO_NID is detected.
>>>
>>> Suggested-by: David Hildenbrand <david@redhat.com>
>>> Signed-off-by: Jia He <justin.he@arm.com>
>>> ---
>>>  arch/arm64/mm/numa.c | 5 +++--
>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
>>> index aafcee3e3f7e..7eeb31740248 100644
>>> --- a/arch/arm64/mm/numa.c
>>> +++ b/arch/arm64/mm/numa.c
>>> @@ -464,10 +464,11 @@ void __init arm64_numa_init(void)
>>>  
>>>  /*
>>>   * We hope that we will be hotplugging memory on nodes we already know about,
>>> - * such that acpi_get_node() succeeds and we never fall back to this...
>>> + * such that acpi_get_node() succeeds. But when SRAT is not present, the node
>>> + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option.
>>>   */
>>>  int memory_add_physaddr_to_nid(u64 addr)
>>>  {
>>> -	pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
>>>  	return 0;
>>>  }
>>> +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
>>
>> Does it make sense to export a noop function? Wouldn't make more sense
>> to simply make it static inline somewhere in a header? I haven't checked
>> whether there is an easy way to do that sanely bu this just hit my eyes.
> 
> We'll need to either add a CONFIG_ option or arch specific callback to
> make both non-empty (x86, powerpc, ia64) and empty (arm64, sh)
> implementations coexist ...

Note: I have a similar dummy (return 0) patch for s390x lying around here.


-- 
Thanks,

David / dhildenb