> On Nov 7, 2022, at 10:10, Naoya Horiguchi <naoya.horiguchi@xxxxxxxxx> wrote:
>
> From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
>
> The following bug is reported to be triggered when starting X on x86-32
> system with i915:
>
> [ 225.777375] kernel BUG at mm/memory.c:2664!
> [ 225.777391] invalid opcode: 0000 [#1] PREEMPT SMP
> [ 225.777405] CPU: 0 PID: 2402 Comm: Xorg Not tainted 6.1.0-rc3-bdg+ #86
> [ 225.777415] Hardware name: /8I865G775-G, BIOS F1 08/29/2006
> [ 225.777421] EIP: __apply_to_page_range+0x24d/0x31c
> [ 225.777437] Code: ff ff 8b 55 e8 8b 45 cc e8 0a 11 ec ff 89 d8 83 c4 28 5b 5e 5f 5d c3 81 7d e0 a0 ef 96 c1 74 ad 8b 45 d0 e8 2d 83 49 00 eb a3 <0f> 0b 25 00 f0 ff ff 81 eb 00 00 00 40 01 c3 8b 45 ec 8b 00 e8 76
> [ 225.777446] EAX: 00000001 EBX: c53a3b58 ECX: b5c00000 EDX: c258aa00
> [ 225.777454] ESI: b5c00000 EDI: b5900000 EBP: c4b0fdb4 ESP: c4b0fd80
> [ 225.777462] DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068 EFLAGS: 00010202
> [ 225.777470] CR0: 80050033 CR2: b5900000 CR3: 053a3000 CR4: 000006d0
> [ 225.777479] Call Trace:
> [ 225.777486] ? i915_memcpy_init_early+0x63/0x63 [i915]
> [ 225.777684] apply_to_page_range+0x21/0x27
> [ 225.777694] ? i915_memcpy_init_early+0x63/0x63 [i915]
> [ 225.777870] remap_io_mapping+0x49/0x75 [i915]
> [ 225.778046] ? i915_memcpy_init_early+0x63/0x63 [i915]
> [ 225.778220] ? mutex_unlock+0xb/0xd
> [ 225.778231] ? i915_vma_pin_fence+0x6d/0xf7 [i915]
> [ 225.778420] vm_fault_gtt+0x2a9/0x8f1 [i915]
> [ 225.778644] ? lock_is_held_type+0x56/0xe7
> [ 225.778655] ? lock_is_held_type+0x7a/0xe7
> [ 225.778663] ? 0xc1000000
> [ 225.778670] __do_fault+0x21/0x6a
> [ 225.778679] handle_mm_fault+0x708/0xb21
> [ 225.778686] ? mt_find+0x21e/0x5ae
> [ 225.778696] exc_page_fault+0x185/0x705
> [ 225.778704] ? doublefault_shim+0x127/0x127
> [ 225.778715] handle_exception+0x130/0x130
> [ 225.778723] EIP: 0xb700468a
>
> Recently pud_huge() got aware of non-present entry by commit 3a194f3f8ad0
> ("mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present
> pud entry") to handle some special states of gigantic page. However, it's
> overlooked that pud_none() always returns false when running with 2-level
> paging, and as a result pmd_huge() can return true pointlessly.
>
> Introduce "#if CONFIG_PGTABLE_LEVELS > 2" to pud_huge() to deal with this.
>
> Fixes: 3a194f3f8ad0 ("mm/hugetlb: make pud_huge() and follow_huge_pud() aware of non-present pud entry")
> Reported-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Thanks.
