Messages in this thread | | | Date | Wed, 11 Sep 2019 08:49:26 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] driver core: ensure a device has valid node id in device_add() |
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On Wed 11-09-19 14:15:51, Yunsheng Lin wrote: > On 2019/9/11 13:33, Michal Hocko wrote: > > On Tue 10-09-19 14:53:39, Michal Hocko wrote: > >> On Tue 10-09-19 20:47:40, Yunsheng Lin wrote: > >>> On 2019/9/10 19:12, Greg KH wrote: > >>>> On Tue, Sep 10, 2019 at 01:04:51PM +0200, Michal Hocko wrote: > >>>>> On Tue 10-09-19 18:58:05, Yunsheng Lin wrote: > >>>>>> On 2019/9/10 17:31, Greg KH wrote: > >>>>>>> On Tue, Sep 10, 2019 at 02:43:32PM +0800, Yunsheng Lin wrote: > >>>>>>>> On 2019/9/9 17:53, Greg KH wrote: > >>>>>>>>> On Mon, Sep 09, 2019 at 02:04:23PM +0800, Yunsheng Lin wrote: > >>>>>>>>>> Currently a device does not belong to any of the numa nodes > >>>>>>>>>> (dev->numa_node is NUMA_NO_NODE) when the node id is neither > >>>>>>>>>> specified by fw nor by virtual device layer and the device has > >>>>>>>>>> no parent device. > >>>>>>>>> > >>>>>>>>> Is this really a problem? > >>>>>>>> > >>>>>>>> Not really. > >>>>>>>> Someone need to guess the node id when it is not specified, right? > >>>>>>> > >>>>>>> No, why? Guessing guarantees you will get it wrong on some systems. > >>>>>>> > >>>>>>> Are you seeing real problems because the id is not being set? What > >>>>>>> problem is this fixing that you can actually observe? > >>>>>> > >>>>>> When passing the return value of dev_to_node() to cpumask_of_node() > >>>>>> without checking the node id if the node id is not valid, there is > >>>>>> global-out-of-bounds detected by KASAN as below: > >>>>> > >>>>> OK, I seem to remember this being brought up already. And now when I > >>>>> think about it, we really want to make cpumask_of_node NUMA_NO_NODE > >>>>> aware. That means using the same trick the allocator does for this > >>>>> special case. > >>>> > >>>> That seems reasonable to me, and much more "obvious" as to what is going > >>>> on. > >>>> > >>> > >>> Ok, thanks for the suggestion. > >>> > >>> For arm64 and x86, there are two versions of cpumask_of_node(). > >>> > >>> when CONFIG_DEBUG_PER_CPU_MAPS is defined, the cpumask_of_node() > >>> in arch/x86/mm/numa.c is used, which does partial node id checking: > >>> > >>> const struct cpumask *cpumask_of_node(int node) > >>> { > >>> if (node >= nr_node_ids) { > >>> printk(KERN_WARNING > >>> "cpumask_of_node(%d): node > nr_node_ids(%u)\n", > >>> node, nr_node_ids); > >>> dump_stack(); > >>> return cpu_none_mask; > >>> } > >>> if (node_to_cpumask_map[node] == NULL) { > >>> printk(KERN_WARNING > >>> "cpumask_of_node(%d): no node_to_cpumask_map!\n", > >>> node); > >>> dump_stack(); > >>> return cpu_online_mask; > >>> } > >>> return node_to_cpumask_map[node]; > >>> } > >>> > >>> when CONFIG_DEBUG_PER_CPU_MAPS is undefined, the cpumask_of_node() > >>> in arch/x86/include/asm/topology.h is used: > >>> > >>> static inline const struct cpumask *cpumask_of_node(int node) > >>> { > >>> return node_to_cpumask_map[node]; > >>> } > >> > >> I would simply go with. There shouldn't be any need for heavy weight > >> checks that CONFIG_DEBUG_PER_CPU_MAPS has. > >> > >> static inline const struct cpumask *cpumask_of_node(int node) > >> { > >> /* A nice comment goes here */ > >> if (node == NUMA_NO_NODE) > > How about "(unsigned int)node >= nr_node_ids", this is suggested > by Peter, it checks the case where the node id set by fw is bigger > or equal than nr_node_ids, and still handle the < 0 case, which > includes NUMA_NO_NODE.
Isn't that a plain bug? Is something like that really happening?
> Maybe define a macro like below to do that in order to do > the node checking consistently through kernel: > > #define numa_node_valid(node) ((unsigned int)(node) < nr_node_ids) > > > >> return node_to_cpumask_map[numa_mem_id()]; > >> return node_to_cpumask_map[node]; > >> } > > > > Sleeping over this and thinking more about the actual semantic the above > > is wrong. We cannot really copy the page allocator logic. Why? 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. > > From below, if the __GFP_THISNODE is set, the fallback is not performed.
__GFP_THISNODE is a very specific situation when the caller knows which node should be used for the allocation. NUMA_NO_NODE && __GFP_THISNODE is a bug and I would dare to call it an undefined behavior.
> For node_to_cpumask_map() case, maybe we can return the cpumask that is > on the node of cpu_to_node(raw_smp_processor_id()) for NUMA_NO_NODE, > because the current cpu does belong to a node, and the node does have at > least one cpu, which is the cpu is calling the node_to_cpumask_map(). > > Make any sense?
No. Please read the above paragraph again. NUMA_NO_NODE really means no node affinity. So all cpus should be usable. Making any assumptions about a local context is just wrong. -- Michal Hocko SUSE Labs
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