Re: [PATCH] virtio_net: Abort driver initialization if device fails

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 29, 2022 at 04:49:02AM +0000, Eli Cohen wrote:
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Sunday, August 28, 2022 11:08 PM
> > To: Eli Cohen <elic@nvidia.com>
> > Cc: jasowang@redhat.com; eperezma@redhat.com; si-wei.liu@oracle.com;
> > virtualization@lists.linux-foundation.org
> > Subject: Re: [PATCH] virtio_net: Abort driver initialization if device fails
> > 
> > On Sun, Aug 28, 2022 at 06:48:20PM +0300, Eli Cohen wrote:
> > > Read the status bit after virtio_device_ready() to check if device
> > > initialization was successful. If it was not, abort driver
> > > initialization to avoid further attempts to access device resources.
> > >
> > > Abort is required per virtio spec v1.1
> > >
> > > 3.1.1
> > > ...
> > > If any of these steps go irrecoverably wrong, the driver SHOULD set the
> > > FAILED status bit to indicate that it has given up on the device (it can
> > > reset the device later to restart if desired). The driver MUST NOT
> > > continue initialization in that case.
> > 
> > I don't see a requirement to read the status bit though
> > which is what the patch does.
> > 
> 
> No explicit requirement to read the status but we are required to abort in
> case of a failure and reading the status seems legitimate way to detect this situation.

Isn't this supposed to be VIRTIO_CONFIG_S_NEEDS_RESET then?


Here's my analysis:

	device might set VIRTIO_CONFIG_S_NEEDS_RESET on failure.
	Normally it will assert a config change interrupt allowing
	us to check that.

	However, if failure triggers before DRIVER_OK it set,
	interrupt can not be sent.

	To address this, check after DRIVER_OK.

Maybe add a comment along these lines.

 Also how about doing this check inside virtio_device_ready and
marking device as broken, and returning error code?


> > > This fixes an issue that was discovered when mlx5_vdpa initialization
> > > failed due to firmware error
> > 
> > A bit more detail would be nice. which function failed exactly?
> > 
> > > and subsequent attempts to send control VQ
> > > commands failed with a call trace:
> > >
> > >  watchdog: BUG: soft lockup - CPU#62 stuck for 26s! [systemd-udevd:2610]
> > >  Modules linked in: virtio_net(+) net_failover failover virtio_vdpa
> > mlx5_vdpa vringh vhost_iotlb vdpa mlx5_ib ib_uverbs ib_core mlx5_core
> > mlxfw psample tls pci>
> > >   drm ghash_clmulni_intel serio_raw usb_storage scsi_transport_sas hpwdt
> > wmi target_core_mod [last unloaded: ib_core]
> > >  CPU: 62 PID: 2610 Comm: systemd-udevd Tainted: G I        6.0.0-rc2+ #7
> > >  Hardware name: HPE ProLiant DL380 Gen10/ProLiant DL380 Gen10, BIOS
> > U30 04/08/2020
> > >  RIP: 0010:virtnet_send_command+0xfa/0x140 [virtio_net]
> > >  Code: ec f0 80 e0 85 c0 0f 88 0c 68 00 00 48 8b 7b 08 e8 9b d6 80 e0 84 c0
> > 75 11 eb 43 48 8b 7b 08 e8 7c c3 80 e0 84 c0 75 15 f3 90 <48> 8b 7b 08 48 8d
> > 74 24 >
> > >  RSP: 0018:ffffb6fba2037b78 EFLAGS: 00000246
> > >  RAX: 0000000000000000 RBX: ffff99c6043a99c0 RCX: 0000000000000000
> > >  RDX: 0000000000000000 RSI: ffffb6fba2037b7c RDI: ffff99c6042c6500
> > >  RBP: ffffb6fba2037bc0 R08: 0000000000000001 R09: 0000000000000000
> > >  R10: 0000000000000003 R11: 0000000000000002 R12: 0000000000000002
> > >  R13: 0000000000000004 R14: 0000000000000000 R15: ffff99f634258400
> > >  FS:  00007f5894eefb40(0000) GS:ffff99dd9fb80000(0000)
> > knlGS:0000000000000000
> > >  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > >  CR2: 000055acd4a80000 CR3: 00000018605a4002 CR4: 00000000007706e0
> > >  DR0: 0000000000000000 DR1: 0000000000000000 DR2:
> > 0000000000000000
> > >  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > >  PKRU: 55555554
> > >  Call Trace:
> > >   <TASK>
> > >   _virtnet_set_queues+0x7f/0xc0 [virtio_net]
> > >   virtnet_probe+0x989/0xae0 [virtio_net]
> > >   virtio_dev_probe+0x1ab/0x260
> > >   really_probe+0xde/0x390
> > >   ? pm_runtime_barrier+0x50/0x90
> > >   __driver_probe_device+0x78/0x180
> > >   driver_probe_device+0x1e/0x90
> > >   __driver_attach+0xc4/0x1e0
> > >   ? __device_attach_driver+0xe0/0xe0
> > >   ? __device_attach_driver+0xe0/0xe0
> > >   bus_for_each_dev+0x61/0x90
> > >   bus_add_driver+0x1a9/0x200
> > >   driver_register+0x8f/0xf0
> > >   ? 0xffffffffc0fdb000
> > >   virtio_net_driver_init+0x70/0x1000 [virtio_net]
> > >   do_one_initcall+0x41/0x210
> > >   ? kmem_cache_alloc_trace+0x16d/0x2c0
> > >   do_init_module+0x4c/0x1f0
> > >   __do_sys_finit_module+0x9f/0x100
> > >   do_syscall_64+0x38/0x90
> > >   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > >  RIP: 0033:0x7f589510aecd
> > >  Code: 5b 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48
> > 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01
> > >
> > >  RSP: 002b:00007ffde61fb398 EFLAGS: 00000246 ORIG_RAX:
> > 0000000000000139
> > >  RAX: ffffffffffffffda RBX: 000055acd48ac950 RCX: 00007f589510aecd
> > >  RDX: 0000000000000000 RSI: 00007f589584332c RDI: 0000000000000012
> > >  RBP: 0000000000020000 R08: 0000000000000000 R09: 0000000000000002
> > >  R10: 0000000000000012 R11: 0000000000000246 R12: 00007f589584332c
> > >  R13: 000055acd4867c70 R14: 0000000000000007 R15: 000055acd48980a0
> > >   </TASK>
> > >
> > > Fixes: commit 4baf1e33d084 ("virtio_net: enable VQs early")
> > > Signed-off-by: Eli Cohen <elic@nvidia.com>
> > > ---
> > >  drivers/net/virtio_net.c | 7 ++++++-
> > >  1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 9cce7dec7366..4698d9a28a6f 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -3900,6 +3900,11 @@ static int virtnet_probe(struct virtio_device
> > *vdev)
> > >  	}
> > >
> > >  	virtio_device_ready(vdev);
> > > +	if (vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_FAILED) {
> > > +		err = -EINVAL;
> > > +		rtnl_unlock();
> > > +		goto unregister_ndev;
> > > +	}
> > >
> > >  	rtnl_unlock();
> > >
> > 
> > I don't get it. What set the failed status?
> > 
> > 
> > > @@ -3934,7 +3939,7 @@ static int virtnet_probe(struct virtio_device
> > *vdev)
> > >
> > >  free_unregister_netdev:
> > >  	virtio_reset_device(vdev);
> > > -
> > > +unregister_ndev:
> > >  	unregister_netdev(dev);
> > >  free_failover:
> > >  	net_failover_destroy(vi->failover);
> > > --
> > > 2.35.1
> 

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