Re: [PATCH V2 2/2] net: Fixup virtnet_set_affinity() cause cpumask warning

[Guo Ren]

On Mon, Oct 17, 2022 at 10:00 AM Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx> wrote:
>
> On Thu, 13 Oct 2022 23:04:59 -0400, guoren@xxxxxxxxxx wrote:
> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> >
> > Don't pass nr_bits-1 as arg1 for cpumask_next_wrap, which would
> > cause warning now 78e5a3399421 ("cpumask: fix checking valid
> > cpu range").
> >
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 1 at include/linux/cpumask.h:110 cpumask_next_wrap+0x5c/0x80
> > Modules linked in:
> > CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.0.0-11659-ge7e38f6cce55-dirty #328
> > Hardware name: riscv-virtio,qemu (DT)
> > epc : cpumask_next_wrap+0x5c/0x80
> >  ra : virtnet_set_affinity+0x1ba/0x1fc
> > epc : ffffffff808992ca ra : ffffffff805d84ca sp : ff60000002327a50
> >  gp : ffffffff81602390 tp : ff600000023a0000 t0 : 5f74656e74726976
> >  t1 : 0000000000000000 t2 : 735f74656e747269 s0 : ff60000002327a90
> >  s1 : 0000000000000003 a0 : 0000000000000003 a1 : ffffffff816051c0
> >  a2 : 0000000000000004 a3 : 0000000000000000 a4 : 0000000000000000
> >  a5 : 0000000000000004 a6 : 0000000000000000 a7 : 0000000000000000
> >  s2 : 0000000000000000 s3 : ffffffff816051c0 s4 : ffffffff8160224c
> >  s5 : 0000000000000004 s6 : 0000000000000004 s7 : 0000000000000000
> >  s8 : 0000000000000003 s9 : ffffffff810aa398 s10: ffffffff80e97d20
> >  s11: 0000000000000004 t3 : ffffffff819acc97 t4 : ffffffff819acc97
> >  t5 : ffffffff819acc98 t6 : ff60000002327878
> > status: 0000000200000120 badaddr: 0000000000000000 cause: 0000000000000003
> > [<ffffffff805d84ca>] virtnet_set_affinity+0x1ba/0x1fc
> > [<ffffffff805da7ac>] virtnet_probe+0x832/0xf1e
> > [<ffffffff804fe61c>] virtio_dev_probe+0x164/0x2de
> > [<ffffffff8054c4c4>] really_probe+0x82/0x224
> > [<ffffffff8054c6c0>] __driver_probe_device+0x5a/0xaa
> > [<ffffffff8054c73c>] driver_probe_device+0x2c/0xb8
> > [<ffffffff8054cd66>] __driver_attach+0x76/0x108
> > [<ffffffff8054a482>] bus_for_each_dev+0x52/0x9a
> > [<ffffffff8054be8c>] driver_attach+0x1a/0x28
> > [<ffffffff8054b996>] bus_add_driver+0x154/0x1c2
> > [<ffffffff8054d592>] driver_register+0x52/0x108
> > [<ffffffff804fe120>] register_virtio_driver+0x1c/0x2c
> > [<ffffffff80a29142>] virtio_net_driver_init+0x7a/0xb0
> > [<ffffffff80002854>] do_one_initcall+0x66/0x2e4
> > [<ffffffff80a01222>] kernel_init_freeable+0x28a/0x304
> > [<ffffffff808cb1be>] kernel_init+0x1e/0x110
> > [<ffffffff80003c4e>] ret_from_exception+0x0/0x10
> > ---[ end trace 0000000000000000 ]---
> >
> > Fixes: 2ca653d607ce ("virtio_net: Stripe queue affinities across cores.")
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > Signed-off-by: Guo Ren <guoren@xxxxxxxxxx>
> > ---
> >  drivers/net/virtio_net.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index 7106932c6f88..e4b56523b2b5 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -2300,6 +2300,8 @@ static void virtnet_set_affinity(struct virtnet_info *vi)
> >
> >               for (j = 0; j < group_size; j++) {
> >                       cpumask_set_cpu(cpu, mask);
> > +                     if (cpu == (nr_cpu_ids - 1))
> > +                             break;
>
> The problem seems to be a problem with cpumask_next_wrap(), I'm not particularly
> sure.
>
> But I think there is something wrong with your modification, which will cause
> subsequent queues to be bound to (nr_cpu_ids - 1).
Yes, it would lose cpu[nr_cpu_ids - 1]. We've moved to reverting the
patch to fix problem:
https://lore.kernel.org/all/20221015130548.3634468-1-guoren@xxxxxxxxxx/


>
> Thanks.
>
>
> >                       cpu = cpumask_next_wrap(cpu, cpu_online_mask,
> >                                               nr_cpu_ids, false);
> >               }
> > --
> > 2.36.1
> >



-- 
Best Regards
 Guo Ren