Subject: Re: Arm64 crash while reading memory sysfs

From: Mike Rapoport <[email-masked]>
Date: Wed, 26 May 2021 20:24:44 +0300

On Wed, May 26, 2021 at 12:09:14PM +0000, Qian Cai (QUIC) wrote:
> > 
> > On Tue, May 25, 2021 at 03:25:59PM +0000, 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.

Does the issue persist of you only revert the latest patch in the series?
In next-20210525 it would be commit 
89fb47db72f2 ("arm64-drop-pfn_valid_within-and-simplify-pfn_valid-fix")
and commit
dfe215e9bac2 ("arm64: drop pfn_valid_within() and simplify pfn_valid()").

> > Can you please send the beginning of the boot log, up to the
> > 	 "Memory: xK/yK available ..."
> > line?
> 
> [    0.000000] NUMA: Failed to initialise from firmware
> [    0.000000] NUMA: Faking a node at [mem 0x0000000090000000-0x0000009fffffffff]
> [    0.000000] NUMA: NODE_DATA [mem 0x9ffefbabc0-0x9ffefbffff]
> [    0.000000] Zone ranges:
> [    0.000000]   Normal   [mem 0x0000000090000000-0x0000009fffffffff]
> [    0.000000] Movable zone start for each node
> [    0.000000] Early memory node ranges
> [    0.000000]   node   0: [mem 0x0000000090000000-0x0000000091ffffff]
> [    0.000000]   node   0: [mem 0x0000000092000000-0x00000000928fffff]
> [    0.000000]   node   0: [mem 0x0000000092900000-0x00000000fffbffff]
> [    0.000000]   node   0: [mem 0x00000000fffc0000-0x00000000ffffffff]
> [    0.000000]   node   0: [mem 0x0000000880000000-0x0000000fffffffff]
> [    0.000000]   node   0: [mem 0x0000008800000000-0x0000009ff5aeffff]
> [    0.000000]   node   0: [mem 0x0000009ff5af0000-0x0000009ff5b2ffff]
> [    0.000000]   node   0: [mem 0x0000009ff5b30000-0x0000009ff5baffff]
> [    0.000000]   node   0: [mem 0x0000009ff5bb0000-0x0000009ff7deffff]
> [    0.000000]   node   0: [mem 0x0000009ff7df0000-0x0000009ff7e5ffff]
> [    0.000000]   node   0: [mem 0x0000009ff7e60000-0x0000009ff7ffffff]
> [    0.000000]   node   0: [mem 0x0000009ff8000000-0x0000009fffffffff]
> [    0.000000] Initmem setup node 0 [mem 0x0000000090000000-0x0000009fffffffff]
> [    0.000000] mem auto-init: stack:off, heap alloc:on, heap free:off
> [    0.000000] Memory: 777216K/133955584K available (17920K kernel code, 118786K rwdata, 4416K rodata, 6080K init, 67276K bss, 17379072K reserved, 0K cma-reserved)

The available and reserved sizes look weird. Can you post the log with
memblock=debug and mminit_loglevel=4 added to the kernel command line?
 
> > > [1] https://lore.kernel.org/kvmarm/[email-masked]/
> > >
> > > [  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

Do we know what PFN triggers it? Can you please run with this patch:

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 70620d0dd923..b9d1dd0dae5f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1443,6 +1443,12 @@ struct zone *test_pages_in_a_zone(unsigned long start_pfn,
 				i++;
 			if (i == MAX_ORDER_NR_PAGES || pfn + i >= end_pfn)
 				continue;
+
+			if (!pfn_valid(pfn))
+				pr_info("%s: pfn %lx is not valid\n", __func__, pfn);
+			else if (PagePoisoned(pfn_to_page(pfn)))
+				dump_page(pfn_to_page(pfn), "");
+
 			/* Check if we got outside of the zone */
 			if (zone && !zone_spans_pfn(zone, pfn + i))
 				return NULL;

-- 
Sincerely yours,
Mike.

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