Subject: Re: [PATCH] powerpc/mm: update arch_{add,remove}_memory() for radix

From: Nathan Fontenot <[email-masked]>
Date: Thu, 23 Jun 2016 12:27:18 -0500

On 06/23/2016 12:17 PM, Aneesh Kumar K.V wrote:
> Reza Arbab <[email-masked]> writes:
> 
>> These functions are making direct calls to the hash table APIs,
>> leading to a BUG() on systems using radix.
>>
>> Switch them to the vmemmap_{create,remove}_mapping() wrappers, and
>> move to the __meminit section.
> 
> 
> They are really not the same. They can possibly end up using different
> base page size. Also vmemmap is available only with SPARSEMEM_VMEMMAP
> enabled. Does hotplug depend on sparsemem vmemmap ?

Sparse vmemmap is supported, and I think enabled by default for pseries,
but hotplug does not depend on sparse vmemmep.

-Nathan

> 
>>
>> Signed-off-by: Reza Arbab <[email-masked]>
>> ---
>>  arch/powerpc/mm/mem.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
>> index 2fd57fa..80c6ee7 100644
>> --- a/arch/powerpc/mm/mem.c
>> +++ b/arch/powerpc/mm/mem.c
>> @@ -116,7 +116,7 @@ int memory_add_physaddr_to_nid(u64 start)
>>  }
>>  #endif
>>
>> -int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
>> +int __meminit arch_add_memory(int nid, u64 start, u64 size, bool for_device)
>>  {
>>  	struct pglist_data *pgdata;
>>  	struct zone *zone;
>> @@ -127,7 +127,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
>>  	pgdata = NODE_DATA(nid);
>>
>>  	start = (unsigned long)__va(start);
>> -	rc = create_section_mapping(start, start + size);
>> +	rc = vmemmap_create_mapping(start, size, __pa(start));
>>  	if (rc) {
>>  		pr_warning(
>>  			"Unable to create mapping for hot added memory 0x%llx..0x%llx: %d\n",
>> @@ -143,7 +143,7 @@ int arch_add_memory(int nid, u64 start, u64 size, bool for_device)
>>  }
>>
>>  #ifdef CONFIG_MEMORY_HOTREMOVE
>> -int arch_remove_memory(u64 start, u64 size)
>> +int __meminit arch_remove_memory(u64 start, u64 size)
>>  {
>>  	unsigned long start_pfn = start >> PAGE_SHIFT;
>>  	unsigned long nr_pages = size >> PAGE_SHIFT;
>> @@ -157,7 +157,7 @@ int arch_remove_memory(u64 start, u64 size)
>>
>>  	/* Remove htab bolted mappings for this section of memory */
>>  	start = (unsigned long)__va(start);
>> -	ret = remove_section_mapping(start, start + size);
>> +	vmemmap_remove_mapping(start, size);
>>
>>  	/* Ensure all vmalloc mappings are flushed in case they also
>>  	 * hit that section of memory
>> -- 
>> 1.8.3.1
> 
> We really want to look at memory hotplug to fully understand the
> radix impact. The unplug operation needs to do some additional freeing.
> 
> I did put in comments around that with the idea of coming back to that
> later
> 
> #ifdef CONFIG_MEMORY_HOTPLUG
> void radix__vmemmap_remove_mapping(unsigned long start, unsigned long page_size)
> {
> 	/* FIXME!! intel does more. We should free page tables mapping vmemmap ? */
> }
> #endif
> 
> -aneesh
> 
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