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Date:   Tue, 4 Jul 2023 12:43:20 -0400
From:   "Michael S. Tsirkin" <mst@redhat.com>
To:     Maxime Coquelin <maxime.coquelin@redhat.com>
Cc:     xieyongji@bytedance.com, jasowang@redhat.com,
        david.marchand@redhat.com, lulu@redhat.com,
        linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        xuanzhuo@linux.alibaba.com, eperezma@redhat.com
Subject: Re: [PATCH v2 3/3] vduse: Temporarily disable control queue features
Message-ID: <20230704124245-mutt-send-email-mst@kernel.org>
References: <20230704164045.39119-1-maxime.coquelin@redhat.com>
 <20230704164045.39119-4-maxime.coquelin@redhat.com>
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In-Reply-To: <20230704164045.39119-4-maxime.coquelin@redhat.com>
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On Tue, Jul 04, 2023 at 06:40:45PM +0200, Maxime Coquelin wrote:
> Virtio-net driver control queue implementation is not safe
> when used with VDUSE. If the VDUSE application does not
> reply to control queue messages, it currently ends up
> hanging the kernel thread sending this command.
> 
> Some work is on-going to make the control queue
> implementation robust with VDUSE. Until it is completed,
> let's disable control virtqueue and features that depend on
> it.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 1271c9796517..04367a53802b 100644
> --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> @@ -1778,6 +1778,25 @@ static struct attribute *vduse_dev_attrs[] = {
>  
>  ATTRIBUTE_GROUPS(vduse_dev);
>  
> +static void vduse_dev_features_fixup(struct vduse_dev_config *config)
> +{
> +	if (config->device_id == VIRTIO_ID_NET) {
> +		/*
> +		 * Temporarily disable control virtqueue and features that
> +		 * depend on it while CVQ is being made more robust for VDUSE.
> +		 */
> +		config->features &= ~((1ULL << VIRTIO_NET_F_CTRL_VQ) |
> +				(1ULL << VIRTIO_NET_F_CTRL_RX) |
> +				(1ULL << VIRTIO_NET_F_CTRL_VLAN) |
> +				(1ULL << VIRTIO_NET_F_GUEST_ANNOUNCE) |
> +				(1ULL << VIRTIO_NET_F_MQ) |
> +				(1ULL << VIRTIO_NET_F_CTRL_MAC_ADDR) |
> +				(1ULL << VIRTIO_NET_F_RSS) |
> +				(1ULL << VIRTIO_NET_F_HASH_REPORT) |
> +				(1ULL << VIRTIO_NET_F_NOTF_COAL));
> +	}
> +}
> +


This will never be exhaustive, we are adding new features.
Please add an allowlist with just legal ones instead.


>  static int vduse_create_dev(struct vduse_dev_config *config,
>  			    void *config_buf, u64 api_version)
>  {
> @@ -1793,6 +1812,8 @@ static int vduse_create_dev(struct vduse_dev_config *config,
>  	if (!dev)
>  		goto err;
>  
> +	vduse_dev_features_fixup(config);
> +
>  	dev->api_version = api_version;
>  	dev->device_features = config->features;
>  	dev->device_id = config->device_id;
> -- 
> 2.41.0