3:58 a.m.
On Tue, Apr 14, 2020 at 4:51 AM David Hildenbrand <david(a)redhat.com> wrote:
On 11.04.20 02:09, Vishal Verma wrote:
> A misbehaving qemu created a situation where the ACPI SRAT table
> advertised one fewer proximity domains than intended. The NFIT table did
> describe all the expected proximity domains. This caused the device dax
> driver to assign an impossible target_node to the device, and when
> hotplugged as system memory, this would fail with the following
> signature:
>
> [ +0.001627] BUG: kernel NULL pointer dereference, address: 0000000000000088
> [ +0.001331] #PF: supervisor read access in kernel mode
> [ +0.000975] #PF: error_code(0x0000) - not-present page
> [ +0.000976] PGD 80000001767d4067 P4D 80000001767d4067 PUD 10e0c4067 PMD 0
> [ +0.001338] Oops: 0000 [#1] SMP PTI
> [ +0.000676] CPU: 4 PID: 22737 Comm: kswapd3 Tainted: G O
5.6.0-rc5 #9
> [ +0.001457] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
> [ +0.001990] RIP: 0010:prepare_kswapd_sleep+0x7c/0xc0
> [ +0.000780] Code: 89 df e8 87 fd ff ff 89 c2 31 c0 84 d2 74 e6 0f 1f 44
> 00 00 48 8b 05 fb af 7a 01 48 63 93 88 1d 01 00 48 8b
> 84 d0 20 0f 00 00 <48> 3b 98 88 00 00 00 75 28 f0 80 a0
> 80 00 00 00 fe f0 80 a3 38 20
> [ +0.002877] RSP: 0018:ffffc900017a3e78 EFLAGS: 00010202
> [ +0.000805] RAX: 0000000000000000 RBX: ffff8881209e0000 RCX: 0000000000000000
> [ +0.001115] RDX: 0000000000000003 RSI: 0000000000000000 RDI: ffff8881209e0e80
> [ +0.001098] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000008000
> [ +0.001092] R10: 0000000000000000 R11: 0000000000000003 R12: 0000000000000003
> [ +0.001092] R13: 0000000000000003 R14: 0000000000000000 R15: ffffc900017a3ec8
> [ +0.001091] FS: 0000000000000000(0000) GS:ffff888318c00000(0000)
knlGS:0000000000000000
> [ +0.001275] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ +0.000882] CR2: 0000000000000088 CR3: 0000000120b50002 CR4: 00000000001606e0
> [ +0.001095] Call Trace:
> [ +0.000388] kswapd+0x103/0x520
> [ +0.000494] ? finish_wait+0x80/0x80
> [ +0.000547] ? balance_pgdat+0x5a0/0x5a0
> [ +0.000607] kthread+0x120/0x140
> [ +0.000508] ? kthread_create_on_node+0x60/0x60
> [ +0.000706] ret_from_fork+0x3a/0x50
>
> Add a check in the kmem driver to ensure that the target_node for the
> device in question is in the nodes_possible mask.
>
> Cc: Dan Williams <dan.j.williams(a)intel.com>
> Acked-by: Dave Hansen <dave.hansen(a)linux.intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma(a)intel.com>
> ---
> drivers/dax/kmem.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> index 3d0a7e702c94..760c5b4e88c8 100644
> --- a/drivers/dax/kmem.c
> +++ b/drivers/dax/kmem.c
> @@ -32,7 +32,7 @@ int dev_dax_kmem_probe(struct device *dev)
> * unavoidable performance issues.
> */
> numa_node = dev_dax->target_node;
> - if (numa_node < 0) {
> + if (numa_node < 0 || !node_possible(numa_node)) {
> dev_warn(dev, "rejecting DAX region %pR with invalid node:
%d\n",
> res, numa_node);
> return -EINVAL;
>
I do wonder if we should reject that from
add_memory()..->add_memory_resource() instead, where we do the
__try_online_node().
Yes, makes sense to centralize that check internal to
add_memory_resource(). However, instead of a failure let's just pick
the next "closest" possible node with a firmware-workaround
taint-warning to let the admin know when their added memory has an
awkward numa node, but otherwise let the memory come online.