[dpdk-dev] [PATCH] vchost: Notify application of ownership change

[Tetsuya Mukawa]

On 2015/10/25 2:16, Thomas Monjalon wrote:
> 2015-08-12 03:34, Xie, Huawei:
>> On 8/8/2015 1:21 AM, Jan Kiszka wrote:
>>> On VHOST_*_RESET_OWNER, we reinitialize the device but without telling
>>> the application. That will cause crashes when it continues to invoke
>>> vhost services on the device. Fix it by calling the destruction hook if
>>> the device is still in use.
> [...]
>>> --- a/lib/librte_vhost/virtio-net.c
>>> +++ b/lib/librte_vhost/virtio-net.c
>>> @@ -402,6 +402,9 @@ reset_owner(struct vhost_device_ctx ctx)
>>>
>>>  	ll_dev = get_config_ll_entry(ctx);
>>>
>>> +	if ((ll_dev->dev.flags & VIRTIO_DEV_RUNNING))
>>> +		notify_ops->destroy_device(&ll_dev->dev);
>> To me this patch makes sense here.
>> Whether RESET_OWNER is really needed is another question. Whenever the
>> vhost itself needs to process the vhost device, we need to notify the
>> switch application to remove it from data plane.
> Huawei,
> some patches have been accepted for RESET_OWNER management.
> Is this patch obsolete?

Hi Yuanhan and Huawei,

I also have the same question. Do we have a patch for this issue?

Today, I've download Yuanhan's multiple queues patches and applied it on
latest dpdk tree.
Then, tried to apply my vhost PMD patch on it.

When I check the patch, it seems I've faced this issue.
Here are steps to reproduce.

1. Start vhost-user backend application.
     (In my case, testpmd using vhost PMD is the application)
2. Start a VM with vhost-user.
     You can see below message from the backend application.
      VHOST_CONFIG: read message VHOST_USER_SET_VRING_ENABLE
      VHOST_CONFIG: set queue enable: 1 to qp idx: 0
      (snip)
      VHOST_CONFIG: read message VHOST_USER_SET_VRING_KICK
3. After booting Linux on guest, bind the virtio-net device to igb_uio.
    Then below messages are shown.
    VHOST_CONFIG: read message VHOST_USER_RESET_OWNER
    VHOST_CONFIG: read message VHOST_USER_RESET_OWNER
    VHOST_CONFIG: read message VHOST_USER_GET_VRING_BASE

The point is we will have VHOST_USER_RESET_OWNER before
VHOST_USER_GET_VRING_BASE.
Currently, in RESET_OWNER function, all virtio-net data is initialized.
As a result, we also initialize virtio-net flags.
When we get GET_VRING_BASE, we cannot call destroy callback handler
because RUNNING flag has been initialized already.

 I guess when we get RESET_OWNER message, I don't need to do anything.
And all finalizations should be done in GET_VRING_BASE.
(Or some finalizations might be done when next SET_MEM_TABLE is called.)

Thanks,
Tetsuya