linux-kernel - Re: [PATCH] crypto: iaa - Account for cpu-less numa nodes

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Message-ID: <ccb01eb2-7a8f-4635-95ab-df9791c02f51@infradead.org>
Date: Tue, 26 Dec 2023 15:24:42 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Tom Zanussi <tom.zanussi@...ux.intel.com>, herbert@...dor.apana.org.au,
 davem@...emloft.net, fenghua.yu@...el.com
Cc: rex.zhang@...el.com, dave.jiang@...el.com, tony.luck@...el.com,
 linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
 dmaengine@...r.kernel.org
Subject: Re: [PATCH] crypto: iaa - Account for cpu-less numa nodes



On 12/26/23 14:04, Tom Zanussi wrote:
> Hi Randy,
> 
> On Tue, 2023-12-26 at 13:09 -0800, Randy Dunlap wrote:
>> Hi--
>>
>> On 12/26/23 12:53, Tom Zanussi wrote:
>>> In some configurations e.g. systems with CXL, a numa node can have
>>> 0
>>> cpus and cpumask_nth() will return a cpu value that doesn't exist,
>>> which will result in an attempt to add an entry to the wq table at
>>> a
>>> bad index.
>>>
>>> To fix this, when iterating the cpus for a node, skip any node that
>>> doesn't have cpus.
>>>
>>> Also, as a precaution, add a warning and bail if cpumask_nth()
>>> returns
>>> a nonexistent cpu.
>>>
>>> Reported-by: Zhang, Rex <rex.zhang@...el.com>
>>> Signed-off-by: Tom Zanussi <tom.zanussi@...ux.intel.com>
>>> ---
>>>  drivers/crypto/intel/iaa/iaa_crypto_main.c | 14 +++++++++++---
>>>  1 file changed, 11 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/crypto/intel/iaa/iaa_crypto_main.c
>>> b/drivers/crypto/intel/iaa/iaa_crypto_main.c
>>> index 5093361b0107..782157a74043 100644
>>> --- a/drivers/crypto/intel/iaa/iaa_crypto_main.c
>>> +++ b/drivers/crypto/intel/iaa/iaa_crypto_main.c
>>> @@ -1017,12 +1017,17 @@ static void rebalance_wq_table(void)
>>>                 return;
>>>         }
>>>  
>>> -       for_each_online_node(node) {
>>> +       for_each_node_with_cpus(node) {
>>>                 node_cpus = cpumask_of_node(node);
>>>  
>>>                 for (cpu = 0; cpu < nr_cpus_per_node; cpu++) {
>>>                         int node_cpu = cpumask_nth(cpu, node_cpus);
>>>  
>>> +                       if (WARN_ON(node_cpu >= nr_cpu_ids)) {
>>> +                               pr_debug("node_cpu %d doesn't
>>> exist!\n", node_cpu);
>>> +                               return;
>>> +                       }
>>> +
>>>                         if ((cpu % cpus_per_iaa) == 0)
>>>                                 iaa++;
>>>  
>>> @@ -2095,10 +2100,13 @@ static struct idxd_device_driver
>>> iaa_crypto_driver = {
>>>  static int __init iaa_crypto_init_module(void)
>>>  {
>>>         int ret = 0;
>>> +       int node;
>>>  
>>>         nr_cpus = num_online_cpus();
>>> -       nr_nodes = num_online_nodes();
>>> -       nr_cpus_per_node = nr_cpus / nr_nodes;
>>> +       for_each_node_with_cpus(node)
>>> +               nr_nodes++;
>>> +       if (nr_nodes)
>>> +               nr_cpus_per_node = nr_cpus / nr_nodes;
>>
>> If nr_nodes == 0, nr_cpus_per_node is not initialized here.
>> Is it initialized somewhere else, or just not used if nr_nodes is 0?
>>
> 
> nr_cpus_per_node is initialized to 0 elsewhere (as a static global).
> 
> It seems to me nr_nodes should always be at least 1.  From my testing
> with !CONFIG_NUMA, nr_nodes is set to 1 in that case; not sure how you
> can get actually get nr_nodes == 0 if you have any cpus working.  The
> check is there to avoid dividing by 0 but maybe the right thing to is
> BUG_ON(!nr_nodes) and return an error, and remove that check...

I think it's OK as is then.

and I hope that we never see the WARN_ON() up above. :)

>>>  
>>>         if (crypto_has_comp("deflate-generic", 0, 0))
>>>                 deflate_generic_tfm = crypto_alloc_comp("deflate-
>>> generic", 0, 0);
>>
> 

Thanks.
-- 
#Randy