linux-kernel - Re: [PATCH net v3 0/3] vsock/virtio: enable VQs early on probe and finish the setup before using them

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Date:   Thu, 24 Mar 2022 09:20:30 +0000
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>,
        "Michael S. Tsirkin" <mst@...hat.com>, Asias He <asias@...hat.com>,
        Arseny Krasnov <arseny.krasnov@...persky.com>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH net v3 0/3] vsock/virtio: enable VQs early on probe and
 finish the setup before using them

On Wed, Mar 23, 2022 at 06:36:22PM +0100, Stefano Garzarella wrote:
> The first patch fixes a virtio-spec violation. The other two patches
> complete the driver configuration before using the VQs in the probe.
> 
> The patch order should simplify backporting in stable branches.
> 
> v3:
> - re-ordered the patch to improve bisectability [MST]
> 
> v2: https://lore.kernel.org/netdev/20220323084954.11769-1-sgarzare@redhat.com/
> v1: https://lore.kernel.org/netdev/20220322103823.83411-1-sgarzare@redhat.com/
> 
> Stefano Garzarella (3):
>   vsock/virtio: initialize vdev->priv before using VQs
>   vsock/virtio: read the negotiated features before using VQs
>   vsock/virtio: enable VQs early on probe
> 
>  net/vmw_vsock/virtio_transport.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> -- 
> 2.35.1
> 

A subtle point is that we still drop events and rx packets during the
window where DRIVER_OK has been set but vqs haven't been filled.
This is acceptable because it's unavoidable and equivalent to events
happening before DRIVER_OK is set. What this revision *does* fix is that
vq used buffer notifications are no longer lost. Good.

Reviewed-by: Stefan Hajnoczi <stefanha@...hat.com>

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