On 02/19/20 at 11:50am, Andrew Morton wrote:
> On Wed, 19 Feb 2020 11:04:54 +0800 Baoquan He <bhe@xxxxxxxxxx> wrote:
>
> > From: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
> >
> > When we use SPARSEMEM instead of SPARSEMEM_VMEMMAP, pfn_to_page()
> > doesn't work before sparse_init_one_section() is called. This leads to a
> > crash when hotplug memory:
> >
> > [ 41.839170] BUG: unable to handle page fault for address: 0000000006400000
> > [ 41.840663] #PF: supervisor write access in kernel mode
> > [ 41.841822] #PF: error_code(0x0002) - not-present page
> > [ 41.842970] PGD 0 P4D 0
> > [ 41.843538] Oops: 0002 [#1] SMP PTI
> > [ 41.844125] CPU: 3 PID: 221 Comm: kworker/u16:1 Tainted: G W 5.5.0-next-20200205+ #343
> > [ 41.845659] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
> > [ 41.846977] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> > [ 41.847904] RIP: 0010:__memset+0x24/0x30
> > [ 41.848660] Code: cc cc cc cc cc cc 0f 1f 44 00 00 49 89 f9 48 89 d1 83 e2 07 48 c1 e9 03 40 0f b6 f6 48 b8 01 01 01 01 01 01 01 01 48 0f af c6 <f3> 48 ab 89 d1 f3 aa 4c 89 c8 c3 90 49 89 f9 40 88 f0 48 89 d1 f3
> > [ 41.851836] RSP: 0018:ffffb43ac0373c80 EFLAGS: 00010a87
> > [ 41.852686] RAX: ffffffffffffffff RBX: ffff8a1518800000 RCX: 0000000000050000
> > [ 41.853824] RDX: 0000000000000000 RSI: 00000000000000ff RDI: 0000000006400000
> > [ 41.854967] RBP: 0000000000140000 R08: 0000000000100000 R09: 0000000006400000
> > [ 41.856107] R10: 0000000000000000 R11: 0000000000000002 R12: 0000000000000000
> > [ 41.857255] R13: 0000000000000028 R14: 0000000000000000 R15: ffff8a153ffd9280
> > [ 41.858414] FS: 0000000000000000(0000) GS:ffff8a153ab00000(0000) knlGS:0000000000000000
> > [ 41.859703] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [ 41.860627] CR2: 0000000006400000 CR3: 0000000136fca000 CR4: 00000000000006e0
> > [ 41.861716] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > [ 41.862680] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > [ 41.863628] Call Trace:
> > [ 41.863983] sparse_add_section+0x1c9/0x26a
> > [ 41.864570] __add_pages+0xbf/0x150
> > [ 41.865057] add_pages+0x12/0x60
> > [ 41.865489] add_memory_resource+0xc8/0x210
> > [ 41.866017] ? wake_up_q+0xa0/0xa0
> > [ 41.866416] __add_memory+0x62/0xb0
> > [ 41.866825] acpi_memory_device_add+0x13f/0x300
> > [ 41.867410] acpi_bus_attach+0xf6/0x200
> > [ 41.867890] acpi_bus_scan+0x43/0x90
> > [ 41.868448] acpi_device_hotplug+0x275/0x3d0
> > [ 41.868972] acpi_hotplug_work_fn+0x1a/0x30
> > [ 41.869473] process_one_work+0x1a7/0x370
> > [ 41.869953] worker_thread+0x30/0x380
> > [ 41.870396] ? flush_rcu_work+0x30/0x30
> > [ 41.870846] kthread+0x112/0x130
> > [ 41.871236] ? kthread_create_on_node+0x60/0x60
> > [ 41.871770] ret_from_fork+0x35/0x40
> >
> > We should use memmap as it did.
> >
> > Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
> > Signed-off-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
> > Acked-by: David Hildenbrand <david@xxxxxxxxxx>
> > Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
> > CC: Dan Williams <dan.j.williams@xxxxxxxxx>
>
> This should have included your signed-off-by, as you were on the patch
> delivery path. I have made that change to my copy of the patch - is
> that OK?
OK, thanks.
>
> I also added a cc:stable. Do we agree this is appropriate?
Agree, this breakage happened since subsection hotplug.
>
> I added Dan's "On x86 the impact is limited to x86_32 builds, or x86_64
> configurations that override the default setting for
> SPARSEMEM_VMEMMAP." to the changelog.
Looks good, thanks.
