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

[Adrian Moreno]

Hi Chenbo

On 1/6/21 12:54 PM, Xia, Chenbo wrote:
> Hi Maxime,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin at redhat.com>
>> Sent: Monday, December 21, 2020 5:14 AM
>> To: dev at dpdk.org; Xia, Chenbo <chenbo.xia at intel.com>; olivier.matz at 6wind.com;
>> amorenoz at redhat.com; david.marchand at redhat.com
>> Cc: Maxime Coquelin <maxime.coquelin at 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 at 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?
> 
You're right. Although  set_status(features_ok) should be followed by
get_status() to check if device has set feature_ok bit, the problem is that
set_status is called on device initialization, which would happen even when the
vhost backed is not yet connected (server-mode). Failing there would tear down
the ethdev which would make the future "hotplug" fail. Hopefully this will all
be fixed by Maxime's refactoring :)
So +1 to reconsider improving error propagation here.

> 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
> 

-- 
Adrián Moreno