Re: [PATCH v2 2/3] mm/memory_hotplug: split memmap_on_memory requests across memblocks

[Huang, Ying]

"Verma, Vishal L" <vishal.l.verma@xxxxxxxxx> writes:

> On Mon, 2023-07-24 at 13:54 +0800, Huang, Ying wrote:
>> Vishal Verma <vishal.l.verma@xxxxxxxxx> writes:
>>
>> >
>> > @@ -2035,12 +2056,38 @@ void try_offline_node(int nid)
>> >  }
>> >  EXPORT_SYMBOL(try_offline_node);
>> >
>> > -static int __ref try_remove_memory(u64 start, u64 size)
>> > +static void __ref __try_remove_memory(int nid, u64 start, u64 size,
>> > +                                    struct vmem_altmap *altmap)
>> >  {
>> > -       struct vmem_altmap mhp_altmap = {};
>> > -       struct vmem_altmap *altmap = NULL;
>> > -       unsigned long nr_vmemmap_pages;
>> > -       int rc = 0, nid = NUMA_NO_NODE;
>> > +       /* remove memmap entry */
>> > +       firmware_map_remove(start, start + size, "System RAM");
>>
>> If mhp_supports_memmap_on_memory(), we will call
>> firmware_map_add_hotplug() for whole range.  But here we may call
>> firmware_map_remove() for part of range.  Is it OK?
>>
>
> Good point, this is a discrepancy in the add vs remove path. Can the
> firmware memmap entries be moved up a bit in the add path, and is it
> okay to create these for each memblock? Or should these be for the
> whole range? I'm not familiar with the implications. (I've left it as
> is for v3 for now, but depending on the direction I can update in a
> future rev).

Cced more firmware map developers and maintainers.

Per my understanding, we should create one firmware memmap entry for
each memblock.

--
Best Regards,
Huang, Ying