Re: [dpdk-dev] [PATCH] doc: vhost multi-queue reconnection known issue

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 7/28/20 3:33 AM, Xuan Ding wrote:
> This patch added known issue for vhost multi-queue reconnection
> with virtio-net/virtio-pmd.
> 
> Signed-off-by: Xuan Ding <xuan.ding@intel.com>
> ---
>  doc/guides/rel_notes/known_issues.rst | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/doc/guides/rel_notes/known_issues.rst b/doc/guides/rel_notes/known_issues.rst
> index de0782136..3359cf063 100644
> --- a/doc/guides/rel_notes/known_issues.rst
> +++ b/doc/guides/rel_notes/known_issues.rst
> @@ -888,3 +888,24 @@ Unsuitable IOVA mode may be picked as the default
>  
>  **Driver/Module**:
>     ALL.
> +
> +Vhost multi-queue reconnection failed with QEMU version >= 4.2.0
> +-------------------------------------------------
> +
> +**Description**
> +   It's a QEMU regression bug (bad commit: c6beefd674ff). QEMU only saves
> +   acked features for one vhost-net when vhost quits. When vhost reconnects
> +   to virtio-net/virtio-pmd in multi-queue situations, the features been
> +   set multiple times are not consistent.
> +
> +**Implication**
> +   Vhost cannot reconnect back to virtio-net/virtio-pmd normally.
> +
> +**Resolution/Workaround**:
> +   It is possible to filter the incorrect acked features at vhost-user side.
> +
> +**Affected Environment/Platform**:
> +   ALL.
> +
> +**Driver/Module**:
> +   Virtual Device Poll Mode Driver (PMD).
> 

Thanks for documenting this Qemu issue.

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Maxime