Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL_GPL

[David Hildenbrand <david@redhat.com>]

On 08.07.20 08:22, Mike Rapoport wrote:
> On Tue, Jul 07, 2020 at 09:27:43PM -0700, Dan Williams wrote:
>> On Tue, Jul 7, 2020 at 9:08 PM Justin He <Justin.He@arm.com> wrote:
>> [..]
>>>> Especially for architectures that use memblock info for numa info
>>>> (which seems to be everyone except x86) why not implement a generic
>>>> memory_add_physaddr_to_nid() that does:
>>>>
>>>> int memory_add_physaddr_to_nid(u64 addr)
>>>> {
>>>>         unsigned long start_pfn, end_pfn, pfn = PHYS_PFN(addr);
>>>>         int nid;
>>>>
>>>>         for_each_online_node(nid) {
>>>>                 get_pfn_range_for_nid(nid, &start_pfn, &end_pfn);
>>>>                 if (pfn >= start_pfn && pfn <= end_pfn)
>>>>                         return nid;
>>>>         }
>>>>         return NUMA_NO_NODE;
>>>> }
>>>
>>> Thanks for your suggestion,
>>> Could I wrap the codes and let memory_add_physaddr_to_nid simply invoke
>>> phys_to_target_node()?
>>
>> I think it needs to be the reverse. phys_to_target_node() should call
>> memory_add_physaddr_to_nid() by default, but fall back to searching
>> reserved memory address ranges in memblock. See phys_to_target_node()
>> in arch/x86/mm/numa.c. That one uses numa_meminfo instead of memblock,
>> but the principle is the same i.e. that a target node may not be
>> represented in memblock.memory, but memblock.reserved. I'm working on
>> a patch to provide a function similar to get_pfn_range_for_nid() that
>> operates on reserved memory.
> 
> Do we really need yet another memblock iterator?
> I think only x86 has memory that is not in memblock.memory but only in
> memblock.reserved.

Reading about abusing the memblock allcoator once again in memory
hotplug paths makes me shiver.

-- 
Thanks,

David / dhildenb