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

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Message-ID: <62ec89d8633a9a6814d502eb0a9d44714659d06a.camel@linux.intel.com>
Date: Tue, 26 Dec 2023 16:04:07 -0600
From: Tom Zanussi <tom.zanussi@...ux.intel.com>
To: Randy Dunlap <rdunlap@...radead.org>, 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

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...

Thanks,

Tom

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

-- 
Tom Zanussi <tom.zanussi@...ux.intel.com>