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

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

On 1/13/21 2:43 PM, Adrian Moreno wrote:
> Hi Chenbo
> 
> On 1/6/21 12:54 PM, Xia, Chenbo wrote:
>> 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?
>>
> 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.

Yes, makes sense.
Sorry for not replying earlier, I'm rebasing the series and than will
look at all your comments one by one.

Thanks,
Maxime

>> 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
>>
>