[PATCH 3/3] net/vhost: fix Rx interrupt

[Maxime Coquelin]

On 3/14/23 09:59, David Marchand wrote:
> On Thu, Mar 9, 2023 at 1:38 PM David Marchand <david.marchand at redhat.com> wrote:
>>
>> In the situation when a port was started while no virtio driver was
>> connected, Rx interrupts were broken.
>> They were also broken after a virtio driver reconnects.
>>
>> There were several issues mixed in:
>> - this driver was not exposing a fixed file descriptor per Rx queue,
>>    If a virtio driver was not connected yet, each Rx queue vector was
>>    pointing at a -1 fd, and an application could interpret this as a lack
>>    of Rx interrupt support,
>> - when a virtio driver later (re)connected, this net/vhost driver was
>>    hacking into the EAL layer epoll fd to remove a old vring kickfd and
>>    insert the new vring kickfd. This hack constitutes a layer violation
>>    plus users of rte_eth_dev_rx_intr_ctl_q_get_fd() were not notified of
>>    this change,
>> - in the case of reconnection, because the interrupt handle was
>>    reallocated, a 0 fd was failing to be removed from the EAL layer
>>    epoll fd, which resulted in never fixing the EAL epoll fd,
>>
>> To fix Rx interrupts:
>> - allocating (eth_vhost_install_intr) / releasing
>>    (eth_vhost_uninstall_intr) the interrupt handle is moved when
>>    starting / closing the port, while setting / resetting per rxq fd is
>>    triggered by vhost events via some new helpers (see
>>    eth_vhost_configure_intr and eth_vhost_unconfigure_intr),
>> - a "proxy" epoll fd is created per Rx queue at the time the interrupt
>>    handle is allocated, so applications can start waiting for events on
>>    those fds, even before a virtio driver initialises,
>> - when available, vring kickd are populated in the "proxy" epoll fd,
>>
> 
> Maxime, Chenbo,
> 
> Dukai confirms this series fix it, we can mark this patch as fixing:
> Bugzilla ID: 1135
> 
> Do you want me to respin a series or can you fix when applying?

I can do it while preparing the pull request.

Thanks,
Maxime

> 
>> Fixes: 3f8ff12821e4 ("vhost: support interrupt mode")
>> Fixes: 3d4cd4be577c ("net/vhost: fix interrupt mode")
>> Fixes: d61138d4f0e2 ("drivers: remove direct access to interrupt handle")
>> Cc: stable at dpdk.org
>>
>> Signed-off-by: David Marchand <david.marchand at redhat.com>
> 
> Thanks.
> 
>