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SubjectRe: [PATCH v3 7/8] mips: numa: make node_to_cpumask_map() NUMA_NO_NODE aware for mips
Hi,

On Thu, Sep 12, 2019 at 06:15:33PM +0800, Yunsheng Lin wrote:
> When passing the return value of dev_to_node() to cpumask_of_node()
> without checking the node id if the node id is NUMA_NO_NODE, there is
> global-out-of-bounds detected by KASAN.
>
> From the discussion [1], NUMA_NO_NODE really means no node affinity,
> which also means all cpus should be usable. So the cpumask_of_node()
> should always return all cpus online when user passes the node id
> as NUMA_NO_NODE, just like similar semantic that page allocator handles
> NUMA_NO_NODE.
>
> But we cannot really copy the page allocator logic. Simply because the
> page allocator doesn't enforce the near node affinity. It just picks it
> up as a preferred node but then it is free to fallback to any other numa
> node. This is not the case here and node_to_cpumask_map will only restrict
> to the particular node's cpus which would have really non deterministic
> behavior depending on where the code is executed. So in fact we really
> want to return cpu_online_mask for NUMA_NO_NODE.
>
> Since this arch was already NUMA_NO_NODE aware, this patch only changes
> it to return cpu_online_mask and use NUMA_NO_NODE instead of "-1".
>
> [1] https://lore.kernel.org/patchwork/patch/1125789/
> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
> Suggested-by: Michal Hocko <mhocko@kernel.org>
> ---
> V3: Change to only handle NUMA_NO_NODE, and return cpu_online_mask
> for NUMA_NO_NODE case, and change the commit log to better justify
> the change.
> ---
> arch/mips/include/asm/mach-ip27/topology.h | 4 ++--

Nit: the subject says "mips:", but this patch only touches sgi-ip27 and
loongson is updated as a separate patch. I don't see why both patches
cannot be merged. Moreover, the whole set can be made as a single patch,
IMHO.

> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/mips/include/asm/mach-ip27/topology.h b/arch/mips/include/asm/mach-ip27/topology.h
> index 965f079..04505e6 100644
> --- a/arch/mips/include/asm/mach-ip27/topology.h
> +++ b/arch/mips/include/asm/mach-ip27/topology.h
> @@ -15,8 +15,8 @@ struct cpuinfo_ip27 {
> extern struct cpuinfo_ip27 sn_cpu_info[NR_CPUS];
>
> #define cpu_to_node(cpu) (sn_cpu_info[(cpu)].p_nodeid)
> -#define cpumask_of_node(node) ((node) == -1 ? \
> - cpu_all_mask : \
> +#define cpumask_of_node(node) ((node) == NUMA_NO_NODE ? \
> + cpu_online_mask : \
> &hub_data(node)->h_cpus)
> struct pci_bus;
> extern int pcibus_to_node(struct pci_bus *);
> --
> 2.8.1
>

--
Sincerely yours,
Mike.

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