Messages in this thread | | | Subject | Re: [PATCH] driver core: ensure a device has valid node id in device_add() | From | Yunsheng Lin <> | Date | Wed, 11 Sep 2019 14:15:51 +0800 |
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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.
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. 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?
/* * Allocate pages, preferring the node given as nid. The node must be valid and * online. For more general interface, see alloc_pages_node(). */ static inline struct page * __alloc_pages_node(int nid, gfp_t gfp_mask, unsigned int order) { VM_BUG_ON(nid < 0 || nid >= MAX_NUMNODES); VM_WARN_ON((gfp_mask & __GFP_THISNODE) && !node_online(nid));
return __alloc_pages(gfp_mask, order, nid); }
> > Sorry about the confusion. >> -- >> Michal Hocko >> SUSE Labs >
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