Re: (bisected) [PATCH v2 08/37] mm/hugetlb: check for unreasonable folio sizes when registering hstate

Christophe Leroy
2025-10-09T07:50:38Z

Le 09/10/2025 à 09:22, David Hildenbrand a écrit :
> On 09.10.25 09:14, Christophe Leroy wrote:
>> Hi David,
>>
>> Le 01/09/2025 à 17:03, David Hildenbrand a écrit :
>>> Let's check that no hstate that corresponds to an unreasonable folio
>>> size
>>> is registered by an architecture. If we were to succeed registering, we
>>> could later try allocating an unsupported gigantic folio size.
>>>
>>> Further, let's add a BUILD_BUG_ON() for checking that HUGETLB_PAGE_ORDER
>>> is sane at build time. As HUGETLB_PAGE_ORDER is dynamic on powerpc,
>>> we have
>>> to use a BUILD_BUG_ON_INVALID() to make it compile.
>>>
>>> No existing kernel configuration should be able to trigger this check:
>>> either SPARSEMEM without SPARSEMEM_VMEMMAP cannot be configured or
>>> gigantic folios will not exceed a memory section (the case on sparse).
>>>
>>> Reviewed-by: Zi Yan <ziy@nvidia.com>
>>> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
>>> Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
>>> Signed-off-by: David Hildenbrand <david@redhat.com>
>>
>> I get following warning on powerpc with linus tree, bisected to commit
>> 7b4f21f5e038 ("mm/hugetlb: check for unreasonable folio sizes when
>> registering hstate")
>
> Do you have the kernel config around? Is it 32bit?
>
> That would be helpful.

That's corenet64_smp_defconfig

Boot on QEMU with:

qemu-system-ppc64 -smp 2 -nographic -M ppce500 -cpu e5500 -m 1G

Christophe