Re: [PATCH v4 10/25] virtio: add API to enable VQs early

Andy Grover
2014-11-11T00:45:09Z

On 10/13/2014 12:50 AM, Michael S. Tsirkin wrote:
> virtio spec 0.9.X requires DRIVER_OK to be set before
> VQs are used, but some drivers use VQs before probe
> function returns.
> Since DRIVER_OK is set after probe, this violates the spec.
>
> Even though under virtio 1.0 transitional devices support this
> behaviour, we want to make it possible for those early callers to become
> spec compliant and eventually support non-transitional devices.
>
> Add API for drivers to call before using VQs.
>
> Sets DRIVER_OK internally.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
> include/linux/virtio_config.h | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
> index e8f8f71..e36403b 100644
> --- a/include/linux/virtio_config.h
> +++ b/include/linux/virtio_config.h
> @@ -109,6 +109,23 @@ struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
> return vq;
> }
>
> +/**
> + * virtio_device_ready - enable vq use in probe function
> + * @vdev: the device
> + *
> + * Driver must call this to use vqs in the probe function.
> + *
> + * Note: vqs are enabled automatically after probe returns.
> + */
> +static inline
> +void virtio_device_ready(struct virtio_device *dev)
> +{
> + unsigned status = dev->config->get_status(dev);
> +
> + BUG_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
> + dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
> +}

Getting a BUG when booting via KVM, host Fedora 20, guest Fedora 20.

my config is at:

https://fedorapeople.org/~grover/config-20141110

[ 0.828494] ------------[ cut here ]------------
[ 0.829039] kernel BUG at
/home/agrover/git/kernel/include/linux/virtio_config.h:125!
[ 0.831266] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC
[ 0.831266] Modules linked in:
[ 0.831266] CPU: 1 PID: 30 Comm: kworker/1:1 Not tainted 3.18.0-rc4 #120
[ 0.831266] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 0.831266] Workqueue: events control_work_handler
[ 0.831266] task: ffff88003cd98000 ti: ffff88003cd94000 task.ti:
ffff88003cd94000
[ 0.831266] RIP: 0010:[<ffffffff81445004>] [<ffffffff81445004>]
add_port+0x264/0x410
[ 0.831266] RSP: 0000:ffff88003cd97c78 EFLAGS: 00010202
[ 0.831266] RAX: 0000000000000007 RBX: ffff88003c58c400 RCX:
0000000000000001
[ 0.831266] RDX: 000000000000c132 RSI: ffffffff81a955e9 RDI:
000000000001c132
[ 0.831266] RBP: ffff88003cd97cc8 R08: 0000000000000000 R09:
0000000000000000
[ 0.831266] R10: 0000000000000001 R11: 0000000000000000 R12:
ffff88003c58be00
[ 0.831266] R13: 0000000000000001 R14: ffff8800395ca800 R15:
ffff88003c58c420
[ 0.831266] FS: 0000000000000000(0000) GS:ffff88003fa00000(0000)
knlGS:0000000000000000
[ 0.831266] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 0.831266] CR2: 0000000000000000 CR3: 0000000001c11000 CR4:
00000000000006e0
[ 0.831266] DR0: 0000000000000000 DR1: 0000000000000000 DR2:
0000000000000000
[ 0.831266] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7:
0000000000000400
[ 0.831266] Stack:
[ 0.831266] ffff880000000001 0000000000000292 0000000000000000
0000000000000001
[ 0.831266] ffff88003cd97cc8 ffff88003dfa8a20 ffff88003c58beb8
ffff88003c58be10
[ 0.831266] ffff8800395a2000 0000000000000000 ffff88003cd97d38
ffffffff8144531a
[ 0.831266] Call Trace:
[ 0.831266] [<ffffffff8144531a>] control_work_handler+0x16a/0x3c0
[ 0.831266] [<ffffffff8108b0c8>] ? process_one_work+0x208/0x500
[ 0.831266] [<ffffffff8108b16c>] process_one_work+0x2ac/0x500
[ 0.831266] [<ffffffff8108b0c8>] ? process_one_work+0x208/0x500
[ 0.831266] [<ffffffff8108b68e>] worker_thread+0x2ce/0x4e0
[ 0.831266] [<ffffffff8108b3c0>] ? process_one_work+0x500/0x500
[ 0.831266] [<ffffffff81090b28>] kthread+0xf8/0x100
[ 0.831266] [<ffffffff810bad7d>] ? trace_hardirqs_on+0xd/0x10
[ 0.831266] [<ffffffff81090a30>] ? kthread_stop+0x140/0x140
[ 0.831266] [<ffffffff816ea92c>] ret_from_fork+0x7c/0xb0
[ 0.831266] [<ffffffff81090a30>] ? kthread_stop+0x140/0x140
[ 0.831266] Code: c7 c2 48 31 01 83 48 c7 c6 e9 55 a9 81 e8 55 b4 c6
ff 4d 8b b4 24 58 01 00 00 49 8b 86 e8 04 00 00 4c 89 f7 ff 50 10 a8 04
74 0c <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 49 8b 96 e8 04 00 00 83 c8
[ 0.831266] RIP [<ffffffff81445004>] add_port+0x264/0x410
[ 0.831266] RSP <ffff88003cd97c78>
[ 0.878202] ---[ end trace f98fbb172cc7bbf4 ]---

Thanks -- Andy