linux-kernel - Re: [PATCH v3 7/8] mips: numa: make node_to_cpumask_map() NUMA_NO

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Date:   Sun, 15 Sep 2019 14:51:49 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
CC:     <catalin.marinas@....com>, <will@...nel.org>, <mingo@...hat.com>,
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Subject: Re: [PATCH v3 7/8] mips: numa: make node_to_cpumask_map()
 NUMA_NO_NODE aware for mips

On 2019/9/15 14:46, Mike Rapoport wrote:
> On Sun, Sep 15, 2019 at 02:13:51PM +0800, Yunsheng Lin wrote:
>> On 2019/9/15 13:49, Mike Rapoport wrote:
>>> 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@...wei.com>
>>>> Suggested-by: Michal Hocko <mhocko@...nel.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.
>>
>> Thanks for reviewing.
>>
>> As this patchset touches a few files, which may has different maintainer.
>> I am not sure if a separate patch for different arch will make the merging
>> process easy, or a single patch will make the merging process easy?
> 
> The set makes the same logical change to several definitions of
> cpumask_of_node(). It's appropriate to have all these changes in a single
> patch.

Ok, thanks.
Will have all these changes in a single patch.


>  
>> It can be made as a single patch if a single patch will make the merging
>> process easy.
>>
>>>
>>>>  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
>>>>
>>>
>>
>