Re: [PATCH] arm64: mm: call pagetable dtor when freeing hot-removed page tables

[Kevin Brodsky <kevin.brodsky@arm.com>]

On 22/05/2026 11:36, Vishal Moola wrote:
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 4c8959153ac4..9d42cbddce27 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1441,6 +1441,9 @@ static void free_hotplug_page_range(struct page *page, size_t size,
>>  
>>  static void free_hotplug_pgtable_page(struct page *page)
>>  {
>> +	if (folio_test_pgtable(page_folio(page)))
> This should work.
>
>> +		pagetable_dtor(page_ptdesc(page));
>> +
>>  	free_hotplug_page_range(page, PAGE_SIZE, NULL);
> In the case we presumably have a page table page (ptdesc) at this
> point, we should really be freeing it with pagetable_free() as well.

Agreed, I think this is the right thing to do, something like:

if (folio_test_pgtable(page_folio(page)))
pagetable_dtor_free(page_ptdesc(page)); else
free_hotplug_page_range(page, PAGE_SIZE, NULL);


Strangely enough x86 calls pagetable_free() in both cases.

My series protecting page tables with pkeys has a patch [1] to get
vmemmap to allocate page tables with pagetable_alloc(). The diff above
will require pagetable_*_ctor() to be called as well, but I think that's
the right thing to do anyway. That could be posted as a separate series,
but I'm hesitant due to the lack of NUMA awareness in pagetable_alloc().

- Kevin

[1] https://lore.kernel.org/all/20260526-kpkeys-v8-14-eaaacdacc67c@arm.com/

> Its not a big deal that we don't right now, but losing track of the
> matching allocation/free sites will become a headache when separately
> allocating from struct page.
>
>>  }