On 25.10.16 14:31:00, David Daney wrote:

From: David Daney <david.daney-YGCgFSpz5w/QT0dZR+AlfA@public.gmane.org>

On arm64 NUMA kernels we can pass "numa=off" on the command line to
disable NUMA.  A side effect of this is that kmalloc_node() calls to
non-zero nodes will crash the system with an OOPS:

[    0.000000] [<fffffc00081bba84>] __alloc_pages_nodemask+0xa4/0xe68
[    0.000000] [<fffffc00082163a8>] new_slab+0xd0/0x57c
[    0.000000] [<fffffc000821879c>] ___slab_alloc+0x2e4/0x514
[    0.000000] [<fffffc000823882c>] __slab_alloc+0x48/0x58
[    0.000000] [<fffffc00082195a0>] __kmalloc_node+0xd0/0x2e0
[    0.000000] [<fffffc00081119b8>] __irq_domain_add+0x7c/0x164
[    0.000000] [<fffffc0008b75d30>] its_probe+0x784/0x81c
[    0.000000] [<fffffc0008b75e10>] its_init+0x48/0x1b0
.
.
.

This is caused by code like this in kernel/irq/irqdomain.c

    domain = kzalloc_node(sizeof(*domain) + (sizeof(unsigned int) * size),
                  GFP_KERNEL, of_node_to_nid(of_node));

When NUMA is disabled, the concept of a node is really undefined, so
of_node_to_nid() should unconditionally return NUMA_NO_NODE.

Add __of_force_no_numa() to allow of_node_to_nid() to be forced to
return NUMA_NO_NODE.

The follow on patch will call this new function from the arm64 numa
code.

Didn't that work before? numa=off just maps all mem to node 0. If mem
allocation is requested for another node it should just fall back to a
node with mem (node 0 then). I suspect there is something wrong with
the page initialization, see:

 http://www.spinics.net/lists/arm-kernel/msg535191.html
 https://bugzilla.redhat.com/show_bug.cgi?id=1387793

What is the complete oops?

So I think k*alloc_node() must be able to handle requests to
non-existing nodes. Otherwise your fix is incomplete, assume a failed
of_numa_init() causing a dummy init but still some devices reporting a
node.

-Robert
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