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From: Yunsheng Lin <linyunsheng@huawei.com>
To: Paul Burton <paul.burton@mips.com>
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Subject: Re: [PATCH v6] numa: make node_to_cpumask_map() NUMA_NO_NODE aware
Date: Mon, 23 Sep 2019 10:31:08 +0800
Message-ID: <57b3f143-f83b-f96a-de7b-1eccecc81dbb@huawei.com> (raw)
In-Reply-To: <20190921223818.sodqc2ui7mpt7ig5@pburton-laptop>

On 2019/9/22 6:38, Paul Burton wrote:
> Hi Yunsheng,
> 
> On Tue, Sep 17, 2019 at 08:48:54PM +0800, Yunsheng Lin wrote:
>> When passing the return value of dev_to_node() to cpumask_of_node()
>> without checking if the device's 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.
>>
>> Also there is a debugging version of node_to_cpumask_map() for x86 and
>> arm64, which is only used when CONFIG_DEBUG_PER_CPU_MAPS is defined, this
>> patch changes it to handle NUMA_NO_NODE as normal node_to_cpumask_map().
>>
>> [1] https://lore.kernel.org/patchwork/patch/1125789/
>> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
>> Suggested-by: Michal Hocko <mhocko@kernel.org>
>> Acked-by: Michal Hocko <mhocko@suse.com>
> 
> If you end up sending another revision then I think it would be worth
> replacing -1 with NUMA_NO_NODE in
> arch/mips/include/asm/mach-ip27/topology.h for consistency, but in any
> case:

Perhaps it is better to replace -1 with NUMA_NO_NODE along with cpu_all_mask
-> cpu_online_mask change if the cpu_all_mask -> cpu_online_mask change is
reasonable.

Anyway, will do that if there is another version needed.

> 
>     Acked-by: Paul Burton <paul.burton@mips.com> # MIPS bits

Thanks for that.

> 
> Thanks,
>     Paul
> 
>> ---
>> V6: Drop the cpu_all_mask -> cpu_online_mask change for it seems a
>>     little controversial, may need deeper investigation, and rebased
>>     on the latest linux-next.
>> V5: Drop unsigned "fix" change for x86/arm64, and change comment log
>>     according to Michal's comment.
>> V4: Have all these changes in a single patch.
>> 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.
>> V2: make the node id checking change to other arches too.
>> ---
>>  arch/arm64/include/asm/numa.h                    | 3 +++
>>  arch/arm64/mm/numa.c                             | 3 +++
>>  arch/mips/include/asm/mach-loongson64/topology.h | 4 +++-
>>  arch/s390/include/asm/topology.h                 | 3 +++
>>  arch/x86/include/asm/topology.h                  | 3 +++
>>  arch/x86/mm/numa.c                               | 3 +++
>>  6 files changed, 18 insertions(+), 1 deletion(-)
> 
> .
> 


  reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-17 12:48 Yunsheng Lin
2019-09-21 22:38 ` Paul Burton
2019-09-23  2:31   ` Yunsheng Lin [this message]
2019-09-23 15:15 ` Peter Zijlstra
2019-09-23 15:28   ` Michal Hocko
2019-09-23 15:48     ` Peter Zijlstra
2019-09-23 16:52       ` Michal Hocko
2019-09-23 20:34         ` Peter Zijlstra
2019-09-24  1:29           ` Yunsheng Lin
2019-09-24  9:25             ` Peter Zijlstra
2019-09-24 11:07               ` Yunsheng Lin
2019-09-24 11:28                 ` Peter Zijlstra
2019-09-24 11:44                   ` Yunsheng Lin
2019-09-24 11:58                     ` Peter Zijlstra
2019-09-24 12:09                       ` Yunsheng Lin
2019-09-24  7:47           ` Michal Hocko
2019-09-24  9:17             ` Peter Zijlstra
2019-09-24 10:56               ` Michal Hocko
2019-09-24 11:23                 ` Peter Zijlstra
2019-09-24 11:54                   ` Michal Hocko
2019-09-24 12:09                     ` Peter Zijlstra
2019-09-24 12:25                       ` Michal Hocko
2019-09-24 12:43                         ` Peter Zijlstra
2019-09-24 12:59                           ` Peter Zijlstra
2019-09-24 13:19                             ` Michal Hocko
2019-09-25  9:14                               ` Yunsheng Lin
2019-09-25 10:41                                 ` Peter Zijlstra
2019-10-08  8:38                                   ` Yunsheng Lin
2019-10-09 12:25                                     ` Robin Murphy
2019-10-10  6:07                                       ` Yunsheng Lin
2019-10-10  7:32                                         ` Michal Hocko
2019-10-11  3:27                                           ` Yunsheng Lin
2019-10-11 11:15                                             ` Peter Zijlstra
2019-10-12  6:17                                               ` Yunsheng Lin
2019-10-12  7:40                                                 ` Greg KH
2019-10-12  9:47                                                   ` Yunsheng Lin
2019-10-12 10:40                                                     ` Greg KH
2019-10-12 10:47                                                       ` Greg KH
2019-10-14  8:00                                                         ` Yunsheng Lin
2019-10-14  9:25                                                           ` Greg KH
2019-10-14  9:49                                                             ` Peter Zijlstra
2019-10-14 10:04                                                               ` Greg KH
2019-10-15 10:40                                                             ` Yunsheng Lin
2019-10-15 16:58                                                               ` Greg KH
2019-10-16 12:07                                                                 ` Yunsheng Lin
2019-10-28  9:20                                                   ` Yunsheng Lin
2019-10-29  8:53                                                     ` Michal Hocko
2019-10-30  1:58                                                       ` Yunsheng Lin
2019-10-10  8:56                                       ` Peter Zijlstra
2019-09-25 10:40                               ` Peter Zijlstra
2019-09-25 13:25                                 ` Michal Hocko
2019-09-25 16:31                                   ` Peter Zijlstra
2019-09-25 21:45                                     ` Peter Zijlstra
2019-09-26  9:05                                       ` Peter Zijlstra
2019-09-26 12:10                                         ` Peter Zijlstra
2019-09-26 11:45                                     ` Geert Uytterhoeven
2019-09-26 12:24                                       ` Peter Zijlstra

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