Re: Arm64 crash while reading memory sysfs

[David Hildenbrand]

On 25.05.21 17:25, Qian Cai (QUIC) wrote:
> Reverting the patchset "arm64: drop pfn_valid_within() and simplify pfn_valid()" [1] from today's linux-next fixed a crash while reading files under /sys/devices/system/memory.
>
> [1] https://lore.kernel.org/kvmarm/20210511100550.28178-1-rppt@xxxxxxxxxx/
>
> [  247.669668][ T1443] kernel BUG at include/linux/mm.h:1383!
> [  247.675987][ T1443] Internal error: Oops - BUG: 0 [#1] SMP
> [  247.681472][ T1443] Modules linked in: loop processor efivarfs ip_tables x_tables ext4 mbcache jbd2 dm_mod igb i2c_algo_bit nvme mlx5_core i2c_core nvme_core firmware_class
> [  247.696894][ T1443] CPU: 15 PID: 1443 Comm: ranbug Not tainted 5.13.0-rc3-next-20210524+ #11
> [  247.705326][ T1443] Hardware name: MiTAC RAPTOR EV-883832-X3-0001/RAPTOR, BIOS 1.6 06/28/2020
> [  247.713842][ T1443] pstate: 60000005 (nZCv daif -PAN -UAO -TCO BTYPE=--)
> [  247.720536][ T1443] pc : test_pages_in_a_zone+0x23c/0x300
> [  247.725935][ T1443] lr : test_pages_in_a_zone+0x23c/0x300
> [  247.731327][ T1443] sp : ffff800023f8f670
> [  247.735327][ T1443] x29: ffff800023f8f670 x28: 000000000000a000 x27: 000000000000a000
> [  247.743156][ T1443] x26: ffffffbfffe00000 x25: ffff800011c6f738 x24: dfff800000000000
> [  247.750984][ T1443] x23: 0000000000002000 x22: ffff009f7efa29c0 x21: 0000000000000000
> [  247.758812][ T1443] x20: ffffffffffffffff x19: 0000000000008000 x18: ffff00084f9d3370
> [  247.766640][ T1443] x17: 0000000000000000 x16: 0000000000000007 x15: 0000000000000078
> [  247.774467][ T1443] x14: 0000000000000000 x13: ffff800011c6eea4 x12: ffff60136cee0574
> [  247.782295][ T1443] x11: 1fffe0136cee0573 x10: ffff60136cee0573 x9 : dfff800000000000
> [  247.790123][ T1443] x8 : ffff009b67702b9b x7 : 0000000000000001 x6 : ffff009b67702b98
> [  247.797951][ T1443] x5 : 00009fec9311fa8d x4 : ffff009b67702b98 x3 : 1fffe00109f3a529
> [  247.805778][ T1443] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000034
> [  247.813606][ T1443] Call trace:
> [  247.816738][ T1443]  test_pages_in_a_zone+0x23c/0x300
> [  247.821784][ T1443]  valid_zones_show+0x1e0/0x298
> [  247.826483][ T1443]  dev_attr_show+0x50/0xc8
> [  247.830747][ T1443]  sysfs_kf_seq_show+0x164/0x368
> [  247.835533][ T1443]  kernfs_seq_show+0x130/0x198
> [  247.840143][ T1443]  seq_read_iter+0x344/0xd50
> [  247.844581][ T1443]  kernfs_fop_read_iter+0x32c/0x4a8
> [  247.849625][ T1443]  new_sync_read+0x2bc/0x4e8
> [  247.854063][ T1443]  vfs_read+0x18c/0x340
> [  247.858066][ T1443]  ksys_read+0xf8/0x1e0
> [  247.862068][ T1443]  __arm64_sys_read+0x74/0xa8
> [  247.866591][ T1443]  invoke_syscall.constprop.0+0xdc/0x1d8
> [  247.872072][ T1443]  do_el0_svc+0xe4/0x298
> [  247.876162][ T1443]  el0_svc+0x20/0x30
> [  247.879906][ T1443]  el0_sync_handler+0xb0/0xb8
> [  247.884429][ T1443]  el0_sync+0x178/0x180
> [  247.888435][ T1443] Code: b0005ee1 912b8021 910b0021 97fc57ac (d4210000)
> [  247.895217][ T1443] ---[ end trace 4ff9f5cbe7443f54 ]---
> [  247.900522][ T1443] Kernel panic - not syncing: Oops - BUG: Fatal exception
> [  247.907501][ T1443] SMP: stopping secondary CPUs
> [  247.912122][ T1443] Kernel Offset: disabled
> [  247.916296][ T1443] CPU features: 0x00000251,20000846
> [  247.921340][ T1443] Memory Limit: none
> [  247.925100][ T1443] ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ]---

That hole test_pages_in_a_zone() cruft has to go sooner or later. I have 
getting rid of that on my list (simply storing the single zone if any 
per memory block).

We run into an uninitialized memmap, because the poison check in 
page_zone()->page_to_nid() triggers. I assume the memmap of a memory 
hole does not get initialized properly?

--
Thanks,

David / dhildenb