Oscar Salvador <osalvador@xxxxxxx> writes:
> On Tue, May 14, 2024 at 04:04:42PM +0200, Björn Töpel wrote:
>> +static void __meminit free_vmemmap_storage(struct page *page, size_t size,
>> + struct vmem_altmap *altmap)
>> +{
>> + if (altmap)
>> + vmem_altmap_free(altmap, size >> PAGE_SHIFT);
>> + else
>> + free_pages((unsigned long)page_address(page), get_order(size));
>
> David already pointed this out, but can check
> arch/x86/mm/init_64.c:free_pagetable().
>
> You will see that we have to do some magic for bootmem memory (DIMMs
> which were not hotplugged but already present)
Thank you!
>> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
>> +void __ref vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *altmap)
>> +{
>> + remove_pgd_mapping(start, end, true, altmap);
>> +}
>> +#endif /* CONFIG_SPARSEMEM_VMEMMAP */
>> +#endif /* CONFIG_MEMORY_HOTPLUG */
>
> I will comment on the patch where you add support for hotplug and the
> dependency, but on a track in LSFMM today, we decided that most likely
> we will drop memory-hotplug support for !CONFIG_SPARSEMEM_VMEMMAP
> environments.
> So, since you are adding this plain fresh, please consider to tight the
> hotplug dependency to CONFIG_SPARSEMEM_VMEMMAP.
> As a bonus, you will only have to maintain one flavour of functions.
Ah, yeah, I saw it mentioned on the LSF/MM/BPF topics. Less is
definitely more -- I'll make the next version depend on
SPARSEMEM_VMEMMAP.
Björn
