Re: [mm/debug_vm_pgtable/locks] e2aad6f1d2: BUG:unable_to_handle_page_fault_for_address

[Aneesh Kumar K.V]

On 9/22/20 2:22 PM, Anshuman Khandual wrote:
> On 09/22/2020 09:33 AM, Aneesh Kumar K.V wrote:
> > On 9/21/20 2:51 PM, kernel test robot wrote:
> > > Greeting,
> > >
> > > FYI, we noticed the following commit (built with gcc-9):
> > >
> > > commit: e2aad6f1d232b457ea6a3194992dd4c0a83534a5 ("mm/debug_vm_pgtable/locks: take correct page table lock")
> > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > >
> > >
> > > in testcase: trinity
> > > version: trinity-i386
> > > with following parameters:
> > >
> > >      runtime: 300s
> > >
> > > test-description: Trinity is a linux system call fuzz tester.
> > > test-url: http://codemonkey.org.uk/projects/trinity/
> > >
> > >
> > > on test machine: qemu-system-i386 -enable-kvm -cpu SandyBridge -smp 2 -m 8G
> > >
> > > caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
> > >
> > >
> > > +----------------------------------------------------------------------+------------+------------+
> > > |                                                                      | c50eb1ed65 | e2aad6f1d2 |
> > > +----------------------------------------------------------------------+------------+------------+
> > > | boot_successes                                                       | 0          | 0          |
> > > | boot_failures                                                        | 61         | 17         |
> > > | BUG:workqueue_lockup-pool                                            | 1          |            |
> > > | BUG:sleeping_function_called_from_invalid_context_at_mm/page_alloc.c | 60         | 17         |
> > > | BUG:unable_to_handle_page_fault_for_address                          | 0          | 17         |
> > > | Oops:#[##]                                                           | 0          | 17         |
> > > | EIP:ptep_get                                                         | 0          | 17         |
> > > | Kernel_panic-not_syncing:Fatal_exception                             | 0          | 17         |
> > > +----------------------------------------------------------------------+------------+------------+
> > >
> > >
> > > If you fix the issue, kindly add following tag
> > > Reported-by: kernel test robot <rong.a.chen@xxxxxxxxx>
> > >
> > >
> > > [   28.726464] BUG: sleeping function called from invalid context at mm/page_alloc.c:4822
> > > [   28.727835] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1, name: swapper
> > > [   28.729221] no locks held by swapper/1.
> > > [   28.729954] CPU: 0 PID: 1 Comm: swapper Not tainted 5.9.0-rc3-00324-ge2aad6f1d232b4 #1
> > > [   28.731484] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> > > [   28.732891] Call Trace:
> > > [   28.733295]  ? show_stack+0x48/0x50
> > > [   28.733943]  dump_stack+0x1b/0x1d
> > > [   28.734569]  ___might_sleep+0x205/0x219
> > > [   28.735292]  __might_sleep+0x106/0x10f
> > > [   28.736022]  __alloc_pages_nodemask+0xe0/0x2c8
> > > [   28.736845]  swap_migration_tests+0x62/0x295
> > > [   28.737639]  debug_vm_pgtable+0x587/0x9b5
> > > [   28.738374]  ? pte_advanced_tests+0x267/0x267
> > > [   28.739318]  do_one_initcall+0x129/0x31c
> > > [   28.740023]  ? rcu_read_lock_sched_held+0x46/0x74
> > > [   28.740944]  kernel_init_freeable+0x201/0x250
> > > [   28.741763]  ? rest_init+0xf8/0xf8
> > > [   28.742401]  kernel_init+0xe/0x15d
> > > [   28.743040]  ? rest_init+0xf8/0xf8
> > > [   28.743694]  ret_from_fork+0x1c/0x30
> >
> >
> > This should be fixed by
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/debug_vm_pgtable.c?id=3a4f9a45eadb6ed5fc04686e8db4dc7bb1caec44
> >
> > > [   28.744364] BUG: unable to handle page fault for address: fffbbea4
> > > [   28.745465] #PF: supervisor read access in kernel mode
> > > [   28.746373] #PF: error_code(0x0000) - not-present page
> > > [   28.747275] *pde = 0492b067 *pte = 00000000
> > > [   28.748054] Oops: 0000 [#1]
> > > [   28.748548] CPU: 0 PID: 1 Comm: swapper Tainted: G        W         5.9.0-rc3-00324-ge2aad6f1d232b4 #1
> > > [   28.750188] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
> > > [   28.751641] EIP: ptep_get+0x0/0x3
> > > [   28.752226] Code: 5d fc c9 c3 55 c1 e8 1a 89 e5 53 31 db 83 f8 1f 6a 00 0f 94 c3 b8 80 67 02 c4 31 c9 89 da e8 16 5c f1 ff 89 d8 8b 5d fc c9 c3 <8b> 00 c3 55 31 c9 89 e5 57 56 53 8b 70 04 89 c3 b8 10 68 02 c4 6a
> > > [   28.755465] EAX: fffbbea4 EBX: fffbbea4 ECX: 000047bd EDX: fffbbea4
> > > [   28.756418] ESI: 000047bd EDI: 00000025 EBP: f406bed8 ESP: f406bebc
> > > [   28.757522] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 EFLAGS: 00010286
> > > [   28.758739] CR0: 80050033 CR2: fffbbea4 CR3: 04928000 CR4: 000406d0
> > > [   28.759828] Call Trace:
> > > [   28.760235]  ? hugetlb_advanced_tests+0x2a/0x27f
> > > [   28.761099]  ? do_raw_spin_unlock+0xd7/0x112
> > > [   28.761872]  debug_vm_pgtable+0x927/0x9b5
> > > [   28.762578]  ? pte_advanced_tests+0x267/0x267
> > > [   28.763462]  do_one_initcall+0x129/0x31c
> > > [   28.764134]  ? rcu_read_lock_sched_held+0x46/0x74
> > > [   28.764948]  kernel_init_freeable+0x201/0x250
> > > [   28.765654]  ? rest_init+0xf8/0xf8
> > > [   28.766277]  kernel_init+0xe/0x15d
> > > [   28.766878]  ? rest_init+0xf8/0xf8
> > > [   28.767488]  ret_from_fork+0x1c/0x30
> > > [   28.768052] Modules linked in:
> > > [   28.768532] CR2: 00000000fffbbea4
> > > [   28.769065] ---[ end trace 9c4395cf49c7b3e7 ]---
> >
> > IIUC, Anshuman is reworking the test to follow the page table update rules.
>
> The failure here has been attributed to this particular patch, and
> IIRC we did not see this particular failure before this series.

IIUC that crash is because the usage of pte_t pointer. With  highmem 
that address is unmapped earlier with the series as expected. But 
hugetlb_advanced_test is wrongly using that pointer instead of using a 
pte_t * that should be allocated by huge_pte_alloc().


-aneesh