linux-kernel - Re: [PATCH v3 1/2] cgroup/cpuset: export cpuset_cpus

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Date: Fri, 7 Jun 2024 19:18:06 +0100
From: Frederic Griffoul <griffoul@...il.com>
To: Tejun Heo <tj@...nel.org>
Cc: Waiman Long <longman@...hat.com>, Fred Griffoul <fgriffo@...zon.co.uk>, 
	kernel test robot <lkp@...el.com>, Alex Williamson <alex.williamson@...hat.com>, 
	Zefan Li <lizefan.x@...edance.com>, Johannes Weiner <hannes@...xchg.org>, 
	Jason Gunthorpe <jgg@...pe.ca>, Yi Liu <yi.l.liu@...el.com>, Kevin Tian <kevin.tian@...el.com>, 
	Eric Auger <eric.auger@...hat.com>, Stefan Hajnoczi <stefanha@...hat.com>, 
	Christian Brauner <brauner@...nel.org>, Ankit Agrawal <ankita@...dia.com>, 
	Reinette Chatre <reinette.chatre@...el.com>, Ye Bin <yebin10@...wei.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH v3 1/2] cgroup/cpuset: export cpuset_cpus_allowed()

Thanks. Unfortunately exporting cpuset_cpus_allowed() is not enough.
When CONFIG_CPUSETS is _not_ defined, the function is inline to return
task_cpu_possible_mask(). On arm64 the latter checks the static key
arm64_mismatched_32bit_el0, and thus this symbol must be exported too.

I wonder whether it would be better to avoid inlining cpuset_cpus_allowed()
in this case.

Br,

Fred

On Fri, Jun 7, 2024 at 5:29 PM Tejun Heo <tj@...nel.org> wrote:
>
> On Thu, Jun 06, 2024 at 11:45:37AM -0400, Waiman Long wrote:
> >
> > On 6/6/24 11:10, Fred Griffoul wrote:
> > > A subsequent patch calls cpuset_cpus_allowed() in the vfio driver pci
> > > code. Export the symbol to be able to build the vfio driver as a kernel
> > > module.
> > >
> > > Signed-off-by: Fred Griffoul <fgriffo@...zon.co.uk>
> > > Reported-by: kernel test robot <lkp@...el.com>
> > > Closes: https://lore.kernel.org/oe-kbuild-all/202406060731.L3NSR1Hy-lkp@intel.com/
> > > ---
> > >   kernel/cgroup/cpuset.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> > > index 4237c8748715..9fd56222aa4b 100644
> > > --- a/kernel/cgroup/cpuset.c
> > > +++ b/kernel/cgroup/cpuset.c
> > > @@ -4764,6 +4764,7 @@ void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
> > >     rcu_read_unlock();
> > >     spin_unlock_irqrestore(&callback_lock, flags);
> > >   }
> > > +EXPORT_SYMBOL_GPL(cpuset_cpus_allowed);
> > >   /**
> > >    * cpuset_cpus_allowed_fallback - final fallback before complete catastrophe.
> >
> > LGTM
> >
> > Acked-by: Waiman Long <longman@...hat.com>
>
> Acked-by: Tejun Heo <tj@...nel.org>
>
> If more convenient, please feel free to route the patch with the rest of the
> series. If you want it applied to the cgroup tree, please let me know.
>
> Thanks.
>
> --
> tejun