Re: [dpdk-dev] [PATCH 25/40] net/virtio: add Virtio-user features ops

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi Maxime,

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Monday, December 21, 2020 5:14 AM
> To: dev@dpdk.org; Xia, Chenbo <chenbo.xia@intel.com>; olivier.matz@6wind.com;
> amorenoz@redhat.com; david.marchand@redhat.com
> Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
> Subject: [PATCH 25/40] net/virtio: add Virtio-user features ops
> 
> This patch introduce new callbacks for getting

s/introduce/introduces

> and setting Virtio features, and implements them
> for the different backend types.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  drivers/net/virtio/virtio_user/vhost.h        |   2 +
>  drivers/net/virtio/virtio_user/vhost_kernel.c | 150 +++++++++---------
>  .../net/virtio/virtio_user/vhost_kernel_tap.c |  23 +++
>  .../net/virtio/virtio_user/vhost_kernel_tap.h |   1 +
>  drivers/net/virtio/virtio_user/vhost_user.c   |  63 +++++++-
>  drivers/net/virtio/virtio_user/vhost_vdpa.c   |  38 +++--
>  .../net/virtio/virtio_user/virtio_user_dev.c  |   5 +-
>  drivers/net/virtio/virtio_user_ethdev.c       |   3 +-
>  8 files changed, 188 insertions(+), 97 deletions(-)
> 
> diff --git a/drivers/net/virtio/virtio_user/vhost.h
> b/drivers/net/virtio/virtio_user/vhost.h
> index 8e819ecfb8..16978e27ed 100644
> --- a/drivers/net/virtio/virtio_user/vhost.h
> +++ b/drivers/net/virtio/virtio_user/vhost.h
> @@ -102,6 +102,8 @@ struct virtio_user_dev;
>  struct virtio_user_backend_ops {
>  	int (*setup)(struct virtio_user_dev *dev);
>  	int (*set_owner)(struct virtio_user_dev *dev);
> +	int (*get_features)(struct virtio_user_dev *dev, uint64_t *features);
> +	int (*set_features)(struct virtio_user_dev *dev, uint64_t features);
>  	int (*send_request)(struct virtio_user_dev *dev,
>  			    enum vhost_user_request req,
>  			    void *arg);
> diff --git a/drivers/net/virtio/virtio_user/vhost_kernel.c
> b/drivers/net/virtio/virtio_user/vhost_kernel.c
> index b79dcad179..f44df8ef1f 100644
> --- a/drivers/net/virtio/virtio_user/vhost_kernel.c
> +++ b/drivers/net/virtio/virtio_user/vhost_kernel.c
> @@ -38,6 +38,28 @@ struct vhost_memory_kernel {
>  #define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct vhost_vring_file)
>  #define VHOST_NET_SET_BACKEND _IOW(VHOST_VIRTIO, 0x30, struct
> vhost_vring_file)
> 
> +/* with below features, vhost kernel does not need to do the checksum and TSO,
> + * these info will be passed to virtio_user through virtio net header.
> + */
> +#define VHOST_KERNEL_GUEST_OFFLOADS_MASK	\
> +	((1ULL << VIRTIO_NET_F_GUEST_CSUM) |	\
> +	 (1ULL << VIRTIO_NET_F_GUEST_TSO4) |	\
> +	 (1ULL << VIRTIO_NET_F_GUEST_TSO6) |	\
> +	 (1ULL << VIRTIO_NET_F_GUEST_ECN)  |	\
> +	 (1ULL << VIRTIO_NET_F_GUEST_UFO))
> +
> +/* with below features, when flows from virtio_user to vhost kernel
> + * (1) if flows goes up through the kernel networking stack, it does not need
> + * to verify checksum, which can save CPU cycles;
> + * (2) if flows goes through a Linux bridge and outside from an interface
> + * (kernel driver), checksum and TSO will be done by GSO in kernel or even
> + * offloaded into real physical device.
> + */
> +#define VHOST_KERNEL_HOST_OFFLOADS_MASK		\
> +	((1ULL << VIRTIO_NET_F_HOST_TSO4) |	\
> +	 (1ULL << VIRTIO_NET_F_HOST_TSO6) |	\
> +	 (1ULL << VIRTIO_NET_F_CSUM))
> +
>  static uint64_t max_regions = 64;
> 
>  static void
> @@ -77,10 +99,57 @@ vhost_kernel_set_owner(struct virtio_user_dev *dev)
>  	return vhost_kernel_ioctl(dev->vhostfds[0], VHOST_SET_OWNER, NULL);
>  }
> 
> +static int
> +vhost_kernel_get_features(struct virtio_user_dev *dev, uint64_t *features)
> +{
> +	int ret;
> +	unsigned int tap_features;
> +
> +	ret = vhost_kernel_ioctl(dev->vhostfds[0], VHOST_GET_FEATURES, features);
> +	if (ret < 0) {
> +		PMD_DRV_LOG(ERR, "Failed to get features");
> +		return -1;
> +	}
> +
> +	ret = tap_support_features(&tap_features);
> +	if (ret < 0) {
> +		PMD_DRV_LOG(ERR, "Failed to get TAP features)");

should delete ')' after 'features'?

> +		return -1;
> +	}
> +
> +	/* with tap as the backend, all these features are supported
> +	 * but not claimed by vhost-net, so we add them back when
> +	 * reporting to upper layer.
> +	 */

<snip>

>  	.dma_map = vhost_vdpa_dma_map,
> diff --git a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> index f8e4581951..0a85d058a8 100644
> --- a/drivers/net/virtio/virtio_user/virtio_user_dev.c
> +++ b/drivers/net/virtio/virtio_user/virtio_user_dev.c
> @@ -141,7 +141,7 @@ virtio_user_dev_set_features(struct virtio_user_dev *dev)
>  	/* Strip VIRTIO_NET_F_CTRL_VQ, as devices do not really need to know */
>  	features &= ~(1ull << VIRTIO_NET_F_CTRL_VQ);
>  	features &= ~(1ull << VIRTIO_NET_F_STATUS);
> -	ret = dev->ops->send_request(dev, VHOST_USER_SET_FEATURES, &features);
> +	ret = dev->ops->set_features(dev, features);

I noticed that virtio_user_dev_set_features is called by virtio_user_set_status.
The former may fail but the latter will ignore the failure. So this will happen:
setting features already failed but virtio-user still continue to do things. IMHO, 
this is not very good (similar things may happen for virtio_user_start_device).
What do you think?

Thanks,
Chenbo

>  	if (ret < 0)
>  		goto error;
>  	PMD_DRV_LOG(INFO, "set features: %" PRIx64, features);
> @@ -488,8 +488,7 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char
> *path, int queues,
>  			return -1;
>  		}
> 
> -		if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
> -					   &dev->device_features) < 0) {
> +		if (dev->ops->get_features(dev, &dev->device_features) < 0) {
>  			PMD_INIT_LOG(ERR, "get_features failed: %s",
>  				     strerror(errno));
>  			return -1;
> diff --git a/drivers/net/virtio/virtio_user_ethdev.c
> b/drivers/net/virtio/virtio_user_ethdev.c
> index 283f5c7a36..4d2635c8aa 100644
> --- a/drivers/net/virtio/virtio_user_ethdev.c
> +++ b/drivers/net/virtio/virtio_user_ethdev.c
> @@ -85,8 +85,7 @@ virtio_user_server_reconnect(struct virtio_user_dev *dev)
> 
>  	virtio_set_status(hw, VIRTIO_CONFIG_STATUS_DRIVER);
> 
> -	if (dev->ops->send_request(dev, VHOST_USER_GET_FEATURES,
> -				   &dev->device_features) < 0) {
> +	if (dev->ops->get_features(dev, &dev->device_features) < 0) {
>  		PMD_INIT_LOG(ERR, "get_features failed: %s",
>  			     strerror(errno));
>  		return -1;
> --
> 2.29.2