Test: update readme#27
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Don't merge Signed-off-by: Vishal Kumar <viskuma@qti.qualcomm.com>
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The following race is possible with migration swap entries or
device-private THP entries. e.g. when move_pages is called on a PMD THP
page, then there maybe an intermediate state, where PMD entry acts as
a migration swap entry (pmd_present() is true). Then if an munmap
happens at the same time, then this VM_BUG_ON() can happen in
pmdp_huge_get_and_clear_full().
This patch fixes that.
Thread A: move_pages() syscall
add_folio_for_migration()
mmap_read_lock(mm)
folio_isolate_lru(folio)
mmap_read_unlock(mm)
do_move_pages_to_node()
migrate_pages()
try_to_migrate_one()
spin_lock(ptl)
set_pmd_migration_entry()
pmdp_invalidate() # PMD: _PAGE_INVALID | _PAGE_PTE | pfn
set_pmd_at() # PMD: migration swap entry (pmd_present=0)
spin_unlock(ptl)
[page copy phase] # <--- RACE WINDOW -->
Thread B: munmap()
mmap_write_downgrade(mm)
unmap_vmas() -> zap_pmd_range()
zap_huge_pmd()
__pmd_trans_huge_lock()
pmd_is_huge(): # !pmd_present && !pmd_none -> TRUE (swap entry)
pmd_lock() -> # spin_lock(ptl), waits for Thread A to release ptl
pmdp_huge_get_and_clear_full()
VM_BUG_ON(!pmd_present(*pmdp)) # HITS!
[ 287.738700][ T1867] ------------[ cut here ]------------
[ 287.743843][ T1867] kernel BUG at arch/powerpc/mm/book3s64/pgtable.c:187!
cpu 0x0: Vector: 700 (Program Check) at [c00000044037f4f0]
pc: c000000000094ca4: pmdp_huge_get_and_clear_full+0x6c/0x23c
lr: c000000000645dec: zap_huge_pmd+0xb0/0x868
sp: c00000044037f790
msr: 800000000282b033
current = 0xc0000004032c1a00
paca = 0xc000000004fe0000 irqmask: 0x03 irq_happened: 0x09
pid = 1867, comm = a.out
kernel BUG at :187!
Linux version 6.19.0-12136-g14360d4f917c-dirty (powerpc64le-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40) qualcomm-linux#27 SMP PREEMPT Sun Feb 22 10:38:56 IST 2026
enter ? for help
[link register ] c000000000645dec zap_huge_pmd+0xb0/0x868
[c00000044037f790] c00000044037f7d0 (unreliable)
[c00000044037f7d0] c000000000645dcc zap_huge_pmd+0x90/0x868
[c00000044037f840] c0000000005724cc unmap_page_range+0x176c/0x1f40
[c00000044037fa00] c000000000572ea0 unmap_vmas+0xb0/0x1d8
[c00000044037fa90] c0000000005af254 unmap_region+0xb4/0x128
[c00000044037fb50] c0000000005af400 vms_complete_munmap_vmas+0x138/0x310
[c00000044037fbe0] c0000000005b0f1c do_vmi_align_munmap+0x1ec/0x238
[c00000044037fd30] c0000000005b3688 __vm_munmap+0x170/0x1f8
[c00000044037fdf0] c000000000587f74 sys_munmap+0x2c/0x40
[c00000044037fe10] c000000000032668 system_call_exception+0x128/0x350
[c00000044037fe50] c00000000000d05c system_call_vectored_common+0x15c/0x2ec
---- Exception: 3000 (System Call Vectored) at 0000000010064a2c
SP (7fff9b1ee9c0) is in userspace
0:mon> zh
commit a30b48b ("mm/migrate_device: implement THP migration of zone device pages"),
enabled migration for device-private PMD entries. Hence this is one
other path where this warning could get trigger from.
------------[ cut here ]------------
WARNING: arch/powerpc/mm/book3s64/hash_pgtable.c:199 at hash__pmd_hugepage_update+0x48/0x284, CPU#3: hmm-tests/1905
Modules linked in: test_hmm
CPU: 3 UID: 0 PID: 1905 Comm: hmm-tests Tainted: G B W L N 7.0.0-rc1-01438-g7e2f0ee7581c qualcomm-linux#21 PREEMPT
Tainted: [B]=BAD_PAGE, [W]=WARN, [L]=SOFTLOCKUP, [N]=TEST
Hardware name: IBM pSeries (emulated by qemu) POWER10 (architected) 0x801200 0xf000006 of:SLOF,git-ee03ae pSeries
NIP [c000000000096b70] hash__pmd_hugepage_update+0x48/0x284
LR [c000000000096e7c] hash__pmdp_huge_get_and_clear+0xd0/0xd4
Call Trace:
[c000000604707670] [c000000004e102b8] 0xc000000004e102b8 (unreliable)
[c000000604707700] [c00000000064ec3c] set_pmd_migration_entry+0x414/0x498
[c000000604707760] [c00000000063e5a4] migrate_vma_collect_pmd+0x12e8/0x16c4
[c000000604707890] [c00000000059282c] walk_pgd_range+0x7fc/0xd2c
[c000000604707990] [c000000000592e40] __walk_page_range+0xe4/0x2ac
[c000000604707a10] [c000000000593534] walk_page_range_mm_unsafe+0x204/0x2a4
[c000000604707ab0] [c00000000063af10] migrate_vma_setup+0x1dc/0x2e8
[c000000604707b10] [c008000006a21838] dmirror_migrate_to_system.constprop.0+0x210/0x4b0 [test_hmm]
[c000000604707c30] [c008000006a245b0] dmirror_fops_unlocked_ioctl+0x454/0xa5c [test_hmm]
[c000000604707d20] [c0000000006aab84] sys_ioctl+0x4ec/0x1178
[c000000604707e10] [c0000000000326a8] system_call_exception+0x128/0x350
[c000000604707e50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec
---- interrupt: 3000 at 0x7fffbe44f50c
Fixes: 75358ea ("powerpc/mm/book3s64: Fix MADV_DONTNEED and parallel page fault race")
Fixes: a30b48b ("mm/migrate_device: implement THP migration of zone device pages")
Reported-by: Pavithra Prakash <pavrampu@linux.vnet.ibm.com>
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/9437e5ef28d1e2f5cbdd7f8286350ce93c1d43c5.1773078178.git.ritesh.list@gmail.com
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[ Upstream commit 2a432a6 ] mt7996_vif_link_remove routine is executed by mt76_scan_complete() without holding the wiphy mutex triggering the following lockdep warning. WARNING: CPU: 0 PID: 72 at net/mac80211/key.c:1029 ieee80211_iter_keys+0xe4/0x1a0 [mac80211] CPU: 0 UID: 0 PID: 72 Comm: kworker/u32:2 Tainted: G S 6.18.0-rc5+ qualcomm-linux#27 PREEMPT(full) Tainted: [S]=CPU_OUT_OF_SPEC Hardware name: Default string Default string/SKYBAY, BIOS 5.12 02/15/2023 Workqueue: phy3 mt76_scan_work [mt76] RIP: 0010:ieee80211_iter_keys+0xe4/0x1a0 [mac80211] Code: 4c 48 83 c4 10 5b 5d 41 5c 41 5d 41 5e 41 5f c3 48 8b 47 48 be ff ff ff ff 48 8d 78 68 e8 b4 eb 1e e1 85 c0 0f 85 49 ff ff ff 4c 8b ab 90 1a 00 00 48 8d 83 90 RSP: 0018:ffffc900002f7cb0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888127e00ee0 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff888127e00788 RDI: ffff88811132b5c8 RBP: ffffffffa0ddf400 R08: 0000000000000001 R09: 000000009dcc1dac R10: 0000000000000001 R11: ffff88811132b5a0 R12: ffffc900002f7d00 R13: ffff8882581e6a80 R14: ffff888127e0afc8 R15: ffff888158832038 FS: 0000000000000000(0000) GS:ffff8884da486000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000030a0fd90 CR3: 0000000002c52004 CR4: 00000000003706f0 Call Trace: <TASK> ? lock_acquire+0xc2/0x2c0 mt7996_vif_link_remove+0x64/0x2b0 [mt7996e] mt76_put_vif_phy_link+0x41/0x50 [mt76] mt76_scan_complete+0x77/0x100 [mt76] mt76_scan_work+0x2eb/0x3f0 [mt76] ? process_one_work+0x1e5/0x6d0 process_one_work+0x221/0x6d0 worker_thread+0x19a/0x340 ? rescuer_thread+0x450/0x450 kthread+0x108/0x220 ? kthreads_online_cpu+0x110/0x110 ret_from_fork+0x1c6/0x220 ? kthreads_online_cpu+0x110/0x110 ret_from_fork_asm+0x11/0x20 </TASK> irq event stamp: 45471 hardirqs last enabled at (45477): [<ffffffff813d446e>] __up_console_sem+0x5e/0x70 hardirqs last disabled at (45482): [<ffffffff813d4453>] __up_console_sem+0x43/0x70 softirqs last enabled at (44500): [<ffffffff81f2ae0c>] napi_pp_put_page+0xac/0xd0 softirqs last disabled at (44498): [<ffffffff81fa32a0>] page_pool_put_unrefed_netmem+0x290/0x3d0 ---[ end trace 0000000000000000 ]--- Fix the issue skipping ieee80211_iter_keys() for scanning links in mt7996_vif_link_remove routine since we have not uploaded any hw keys for these links. Fixes: 04414d7 ("wifi: mt76: mt7996: delete vif keys when requested") Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> Tested-by: Ben Greear <greearb@candelatech.com> Link: https://patch.msgid.link/20251115-mt7996-key-iter-link-remove-fix-v1-1-4f3f4e1eaa78@kernel.org Signed-off-by: Felix Fietkau <nbd@nbd.name> Signed-off-by: Sasha Levin <sashal@kernel.org>
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