Re: [PATCH v3 03/11] s390x/mm: Implement arch_remove_memory()

[David Hildenbrand]

On 01.07.19 14:47, Michal Hocko wrote:
> On Mon 01-07-19 09:45:03, Michal Hocko wrote:
>> On Mon 27-05-19 13:11:44, David Hildenbrand wrote:
>>> Will come in handy when wanting to handle errors after
>>> arch_add_memory().
>>
>> I do not understand this. Why do you add a code for something that is
>> not possible on this HW (based on the comment - is it still valid btw?)
> 
> Same as the previous patch (drop it).

No. As the description says, this will be needed to handle errors in
patch 6 cleanly.

And BTW, with paravirtualied devices like virtio-pmem and virtio-mem,
this will also see some other users in the future.

Thanks.

> 
>>> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
>>> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
>>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>> Cc: Michal Hocko <mhocko@xxxxxxxx>
>>> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx>
>>> Cc: David Hildenbrand <david@xxxxxxxxxx>
>>> Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
>>> Cc: Oscar Salvador <osalvador@xxxxxxxx>
>>> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
>>> ---
>>>  arch/s390/mm/init.c | 13 +++++++------
>>>  1 file changed, 7 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>>> index d552e330fbcc..14955e0a9fcf 100644
>>> --- a/arch/s390/mm/init.c
>>> +++ b/arch/s390/mm/init.c
>>> @@ -243,12 +243,13 @@ int arch_add_memory(int nid, u64 start, u64 size,
>>>  void arch_remove_memory(int nid, u64 start, u64 size,
>>>  			struct vmem_altmap *altmap)
>>>  {
>>> -	/*
>>> -	 * There is no hardware or firmware interface which could trigger a
>>> -	 * hot memory remove on s390. So there is nothing that needs to be
>>> -	 * implemented.
>>> -	 */
>>> -	BUG();
>>> +	unsigned long start_pfn = start >> PAGE_SHIFT;
>>> +	unsigned long nr_pages = size >> PAGE_SHIFT;
>>> +	struct zone *zone;
>>> +
>>> +	zone = page_zone(pfn_to_page(start_pfn));
>>> +	__remove_pages(zone, start_pfn, nr_pages, altmap);
>>> +	vmem_remove_mapping(start, size);
>>>  }
>>>  #endif
>>>  #endif /* CONFIG_MEMORY_HOTPLUG */
>>> -- 
>>> 2.20.1
>>>
>>
>> -- 
>> Michal Hocko
>> SUSE Labs
> 


-- 

Thanks,

David / dhildenb