Re: [PATCH 1/2] of, numa: Add function to disable of_node_to_nid().

[Will Deacon]

On Tue, Oct 25, 2016 at 02:31:00PM -0700, David Daney wrote:
> From: David Daney <david.daney@xxxxxxxxxx>
> 
> 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.
> 
> Reported-by: Gilbert Netzer <noname@xxxxxxxxxx>
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> ---
>  drivers/of/of_numa.c | 15 +++++++++++++++
>  include/linux/of.h   |  2 ++
>  2 files changed, 17 insertions(+)
> 
> diff --git a/drivers/of/of_numa.c b/drivers/of/of_numa.c
> index f63d4b0d..2212299 100644
> --- a/drivers/of/of_numa.c
> +++ b/drivers/of/of_numa.c
> @@ -150,12 +150,27 @@ static int __init of_numa_parse_distance_map(void)
>  	return ret;
>  }
>  
> +static bool of_force_no_numa;
> +
> +void __of_force_no_numa(void)
> +{
> +	of_force_no_numa = true;
> +}
> +
>  int of_node_to_nid(struct device_node *device)
>  {
>  	struct device_node *np;
>  	u32 nid;
>  	int r = -ENODATA;
>  
> +	/*
> +	 * If NUMA forced off, nodes are meaningless.  Return
> +	 * NUMA_NO_NODE so that any node specific memory allocations
> +	 * can succeed from the default pool.
> +	 */
> +	if (of_force_no_numa)
> +		return NUMA_NO_NODE;

Why don't you just check if the nid you get back from the device is set in
numa_nodes_parsed and return NUMA_NO_NODE if not?

Will