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

Christophe Leroy
2025-10-09T07:20:35Z

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")

------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at mm/hugetlb.c:4744 hugetlb_add_hstate+0xc0/0x180
Modules linked in:
CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted
6.17.0-rc4-00275-g7b4f21f5e038 #1683 NONE
Hardware name: QEMU ppce500 e5500 0x80240020 QEMU e500
NIP: c000000001357408 LR: c000000001357c90 CTR: 0000000000000003
REGS: c00000000152bad0 TRAP: 0700 Not tainted
(6.17.0-rc4-00275-g7b4f21f5e038)
MSR: 0000000080021002 <CE,ME> CR: 44000448 XER: 20000000
IRQMASK: 1
GPR00: c000000001357c90 c00000000152bd70 c000000001339000 0000000000000012
GPR04: 000000000000000a 0000000000001000 000000000000001e 0000000000000000
GPR08: 0000000000000000 0000000000000000 0000000000000001 000000000000000a
GPR12: c000000001357b68 c000000001590000 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24: c0000000011adb40 c00000000156b528 0000000000000000 c00000000156b4b0
GPR28: c00000000156b528 0000000000000012 0000000040000000 0000000000000000
NIP [c000000001357408] hugetlb_add_hstate+0xc0/0x180
LR [c000000001357c90] hugepagesz_setup+0x128/0x150
Call Trace:
[c00000000152bd70] [c00000000152bda0] init_stack+0x3da0/0x4000 (unreliable)
[c00000000152be10] [c000000001357c90] hugepagesz_setup+0x128/0x150
[c00000000152be80] [c00000000135841c] hugetlb_bootmem_alloc+0x84/0x104
[c00000000152bec0] [c00000000135143c] mm_core_init+0x30/0x174
[c00000000152bf30] [c000000001332ed4] start_kernel+0x540/0x880
[c00000000152bfe0] [c000000000000a50] start_here_common+0x1c/0x20
Code: 2c09000f 39000001 38e00000 39400001 7d00401e 0b080000 281d0001
7d00505e 79080020 0b080000 281d000c 7d4a385e <0b0a0000> 1f5a00b8
38bf0020 3c82ffe8
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at mm/hugetlb.c:4744 hugetlb_add_hstate+0xc0/0x180
Modules linked in:
CPU: 0 UID: 0 PID: 0 Comm: swapper Tainted: G W
6.17.0-rc4-00275-g7b4f21f5e038 #1683 NONE
Tainted: [W]=WARN
Hardware name: QEMU ppce500 e5500 0x80240020 QEMU e500
NIP: c000000001357408 LR: c000000001357c90 CTR: 0000000000000005
REGS: c00000000152bad0 TRAP: 0700 Tainted: G W
(6.17.0-rc4-00275-g7b4f21f5e038)
MSR: 0000000080021002 <CE,ME> CR: 48000448 XER: 20000000
IRQMASK: 1
GPR00: c000000001357c90 c00000000152bd70 c000000001339000 000000000000000e
GPR04: 000000000000000a 0000000000001000 0000000040000000 0000000000000000
GPR08: 0000000000000000 0000000000000001 0000000000000001 0000000000000280
GPR12: c000000001357b68 c000000001590000 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24: c0000000011adb40 c00000000156b5e0 0000000000000001 c00000000156b4b0
GPR28: c00000000156b528 000000000000000e 0000000004000000 00000000000000b8
NIP [c000000001357408] hugetlb_add_hstate+0xc0/0x180
LR [c000000001357c90] hugepagesz_setup+0x128/0x150
Call Trace:
[c00000000152bd70] [c000000000f27048] __func__.0+0x0/0x18 (unreliable)
[c00000000152be10] [c000000001357c90] hugepagesz_setup+0x128/0x150
[c00000000152be80] [c00000000135841c] hugetlb_bootmem_alloc+0x84/0x104
[c00000000152bec0] [c00000000135143c] mm_core_init+0x30/0x174
[c00000000152bf30] [c000000001332ed4] start_kernel+0x540/0x880
[c00000000152bfe0] [c000000000000a50] start_here_common+0x1c/0x20
Code: 2c09000f 39000001 38e00000 39400001 7d00401e 0b080000 281d0001
7d00505e 79080020 0b080000 281d000c 7d4a385e <0b0a0000> 1f5a00b8
38bf0020 3c82ffe8
---[ end trace 0000000000000000 ]---
------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at mm/hugetlb.c:4744 hugetlb_add_hstate+0xc0/0x180
Modules linked in:
CPU: 0 UID: 0 PID: 0 Comm: swapper Tainted: G W
6.17.0-rc4-00275-g7b4f21f5e038 #1683 NONE
Tainted: [W]=WARN
Hardware name: QEMU ppce500 e5500 0x80240020 QEMU e500
NIP: c000000001357408 LR: c000000001357c90 CTR: 0000000000000004
REGS: c00000000152bad0 TRAP: 0700 Tainted: G W
(6.17.0-rc4-00275-g7b4f21f5e038)
MSR: 0000000080021002 <CE,ME> CR: 48000448 XER: 20000000
IRQMASK: 1
GPR00: c000000001357c90 c00000000152bd70 c000000001339000 0000000000000010
GPR04: 000000000000000a 0000000000001000 0000000004000000 0000000000000000
GPR08: 0000000000000000 0000000000000002 0000000000000001 0000000000000a00
GPR12: c000000001357b68 c000000001590000 0000000000000000 0000000000000000
GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR20: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
GPR24: c0000000011adb40 c00000000156b698 0000000000000002 c00000000156b4b0
GPR28: c00000000156b528 0000000000000010 0000000010000000 0000000000000170
NIP [c000000001357408] hugetlb_add_hstate+0xc0/0x180
LR [c000000001357c90] hugepagesz_setup+0x128/0x150
Call Trace:
[c00000000152bd70] [c000000000f27048] __func__.0+0x0/0x18 (unreliable)
[c00000000152be10] [c000000001357c90] hugepagesz_setup+0x128/0x150
[c00000000152be80] [c00000000135841c] hugetlb_bootmem_alloc+0x84/0x104
[c00000000152bec0] [c00000000135143c] mm_core_init+0x30/0x174
[c00000000152bf30] [c000000001332ed4] start_kernel+0x540/0x880
[c00000000152bfe0] [c000000000000a50] start_here_common+0x1c/0x20
Code: 2c09000f 39000001 38e00000 39400001 7d00401e 0b080000 281d0001
7d00505e 79080020 0b080000 281d000c 7d4a385e <0b0a0000> 1f5a00b8
38bf0020 3c82ffe8
---[ end trace 0000000000000000 ]---

> ---
> mm/hugetlb.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 1e777cc51ad04..d3542e92a712e 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -4657,6 +4657,7 @@ static int __init hugetlb_init(void)
>
> BUILD_BUG_ON(sizeof_field(struct page, private) * BITS_PER_BYTE <
> __NR_HPAGEFLAGS);
> + BUILD_BUG_ON_INVALID(HUGETLB_PAGE_ORDER > MAX_FOLIO_ORDER);
>
> if (!hugepages_supported()) {
> if (hugetlb_max_hstate || default_hstate_max_huge_pages)
> @@ -4740,6 +4741,7 @@ void __init hugetlb_add_hstate(unsigned int order)
> }
> BUG_ON(hugetlb_max_hstate >= HUGE_MAX_HSTATE);
> BUG_ON(order < order_base_2(__NR_USED_SUBPAGE));
> + WARN_ON(order > MAX_FOLIO_ORDER);
> h = &hstates[hugetlb_max_hstate++];
> __mutex_init(&h->resize_lock, "resize mutex", &h->resize_key);
> h->order = order;