Re: [dpdk-dev] vhost: add virtio configuration space access socket messages

[Ilya Maximets <i.maximets@samsung.com>]

On 25.02.2019 10:51, Changpeng Liu wrote:
> This patch adds new vhost user messages GET_CONFIG and SET_CONFIG
> used to get/set virtio device's PCI configuration space.

Beside the fact that some additional description and reasoning required,
I do not see the usage of this feature. You're defining the flag
VHOST_USER_PROTOCOL_F_CONFIG, but it's never used. So, none of dpdk vhost
backends (vdpa, vhost-user) will use this feature.
You, probably, missed adding it to VHOST_USER_PROTOCOL_FEATURES or
VDPA_SUPPORTED_PROTOCOL_FEATURES.

>From the other side, current implementation forces application to properly
implement the get/set_config callbacks. Otherwise, receiving of the messages
will result in RTE_VHOST_MSG_RESULT_ERR and subsequent vhost disconnection.
This looks strange, because supported protocol features normally enabled by
default. Am I misunderstood something ?

One more thing. According to spec: "vhost-user slave uses zero length of
payload to indicate an error to vhost-user master". However, current version
of 'vhost_user_get_config' replies with size equal to 'sizeof(uint64_t)'.

Best regards, Ilya Maximets.

> Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
> Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
> ---
>  lib/librte_vhost/rte_vhost.h  |  8 ++++++++
>  lib/librte_vhost/vhost_user.c | 44 +++++++++++++++++++++++++++++++++++++++++++
>  lib/librte_vhost/vhost_user.h | 16 ++++++++++++++++
>  3 files changed, 68 insertions(+)
> 
> diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
> index 2753670..ab710ce 100644
> --- a/lib/librte_vhost/rte_vhost.h
> +++ b/lib/librte_vhost/rte_vhost.h
> @@ -63,6 +63,10 @@
>  #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
>  #endif
>  
> +#ifndef VHOST_USER_PROTOCOL_F_CONFIG
> +#define VHOST_USER_PROTOCOL_F_CONFIG 9
> +#endif
> +
>  #ifndef VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD
>  #define VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD 10
>  #endif
> @@ -173,6 +177,10 @@ struct vhost_device_ops {
>  
>  	int (*vring_state_changed)(int vid, uint16_t queue_id, int enable);	/**< triggered when a vring is enabled or disabled */
>  
> +	int (*get_config)(int vid, uint8_t *config, uint32_t config_len);
> +	int (*set_config)(int vid, uint8_t *config, uint32_t offset,
> +			  uint32_t len, uint32_t flags);
> +
>  	/**
>  	 * Features could be changed after the feature negotiation.
>  	 * For example, VHOST_F_LOG_ALL will be set/cleared at the
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index b086ad9..8e42734 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -73,6 +73,8 @@
>  	[VHOST_USER_NET_SET_MTU]  = "VHOST_USER_NET_SET_MTU",
>  	[VHOST_USER_SET_SLAVE_REQ_FD]  = "VHOST_USER_SET_SLAVE_REQ_FD",
>  	[VHOST_USER_IOTLB_MSG]  = "VHOST_USER_IOTLB_MSG",
> +	[VHOST_USER_GET_CONFIG] = "VHOST_USER_GET_CONFIG",
> +	[VHOST_USER_SET_CONFIG] = "VHOST_USER_SET_CONFIG",
>  	[VHOST_USER_CRYPTO_CREATE_SESS] = "VHOST_USER_CRYPTO_CREATE_SESS",
>  	[VHOST_USER_CRYPTO_CLOSE_SESS] = "VHOST_USER_CRYPTO_CLOSE_SESS",
>  	[VHOST_USER_POSTCOPY_ADVISE]  = "VHOST_USER_POSTCOPY_ADVISE",
> @@ -359,6 +361,46 @@
>  	return RTE_VHOST_MSG_RESULT_OK;
>  }
>  
> +static int
> +vhost_user_get_config(struct virtio_net **pdev, struct VhostUserMsg *msg,
> +		      int main_fd __rte_unused)
> +{
> +	struct virtio_net *dev = *pdev;
> +
> +	if (!dev->notify_ops->get_config) {
> +		msg->size = sizeof(uint64_t);
> +		return RTE_VHOST_MSG_RESULT_REPLY;
> +	}
> +
> +	if (dev->notify_ops->get_config(dev->vid,
> +					msg->payload.config.region,
> +					msg->payload.config.size) != 0) {
> +		msg->size = sizeof(uint64_t);
> +	}
> +
> +	return RTE_VHOST_MSG_RESULT_REPLY;
> +}
> +
> +static int
> +vhost_user_set_config(struct virtio_net **pdev, struct VhostUserMsg *msg,
> +		      int main_fd __rte_unused)
> +{
> +	struct virtio_net *dev = *pdev;
> +
> +	if (!dev->notify_ops->set_config)
> +		return RTE_VHOST_MSG_RESULT_ERR;
> +
> +	if (dev->notify_ops->set_config(dev->vid,
> +					msg->payload.config.region,
> +					msg->payload.config.offset,
> +					msg->payload.config.size,
> +					msg->payload.config.flags) != 0) {
> +		return RTE_VHOST_MSG_RESULT_ERR;
> +	}
> +
> +	return RTE_VHOST_MSG_RESULT_OK;
> +}
> +
>  /*
>   * Reallocate virtio_dev and vhost_virtqueue data structure to make them on the
>   * same numa node as the memory of vring descriptor.
> @@ -1725,6 +1767,8 @@ typedef int (*vhost_message_handler_t)(struct virtio_net **pdev,
>  	[VHOST_USER_NET_SET_MTU] = vhost_user_net_set_mtu,
>  	[VHOST_USER_SET_SLAVE_REQ_FD] = vhost_user_set_req_fd,
>  	[VHOST_USER_IOTLB_MSG] = vhost_user_iotlb_msg,
> +	[VHOST_USER_GET_CONFIG] = vhost_user_get_config,
> +	[VHOST_USER_SET_CONFIG] = vhost_user_set_config,
>  	[VHOST_USER_POSTCOPY_ADVISE] = vhost_user_set_postcopy_advise,
>  	[VHOST_USER_POSTCOPY_LISTEN] = vhost_user_set_postcopy_listen,
>  	[VHOST_USER_POSTCOPY_END] = vhost_user_postcopy_end,
> diff --git a/lib/librte_vhost/vhost_user.h b/lib/librte_vhost/vhost_user.h
> index 2a650fe..057cdec 100644
> --- a/lib/librte_vhost/vhost_user.h
> +++ b/lib/librte_vhost/vhost_user.h
> @@ -12,6 +12,11 @@
>  
>  /* refer to hw/virtio/vhost-user.c */
>  
> +/*
> + * Maximum size of virtio device config space
> + */
> +#define VHOST_USER_MAX_CONFIG_SIZE 256
> +
>  #define VHOST_MEMORY_MAX_NREGIONS 8
>  
>  #define VHOST_USER_PROTOCOL_FEATURES	((1ULL << VHOST_USER_PROTOCOL_F_MQ) | \
> @@ -49,6 +54,8 @@
>  	VHOST_USER_NET_SET_MTU = 20,
>  	VHOST_USER_SET_SLAVE_REQ_FD = 21,
>  	VHOST_USER_IOTLB_MSG = 22,
> +	VHOST_USER_GET_CONFIG = 24,
> +	VHOST_USER_SET_CONFIG = 25,
>  	VHOST_USER_CRYPTO_CREATE_SESS = 26,
>  	VHOST_USER_CRYPTO_CLOSE_SESS = 27,
>  	VHOST_USER_POSTCOPY_ADVISE = 28,
> @@ -60,6 +67,7 @@
>  typedef enum VhostUserSlaveRequest {
>  	VHOST_USER_SLAVE_NONE = 0,
>  	VHOST_USER_SLAVE_IOTLB_MSG = 1,
> +	VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
>  	VHOST_USER_SLAVE_VRING_HOST_NOTIFIER_MSG = 3,
>  	VHOST_USER_SLAVE_MAX
>  } VhostUserSlaveRequest;
> @@ -112,6 +120,13 @@
>  	uint64_t offset;
>  } VhostUserVringArea;
>  
> +typedef struct VhostUserConfig {
> +	uint32_t offset;
> +	uint32_t size;
> +	uint32_t flags;
> +	uint8_t region[VHOST_USER_MAX_CONFIG_SIZE];
> +} VhostUserConfig;
> +
>  typedef struct VhostUserMsg {
>  	union {
>  		uint32_t master; /* a VhostUserRequest value */
> @@ -131,6 +146,7 @@
>  		struct vhost_vring_addr addr;
>  		VhostUserMemory memory;
>  		VhostUserLog    log;
> +		VhostUserConfig config;
>  		struct vhost_iotlb_msg iotlb;
>  		VhostUserCryptoSessionParam crypto_session;
>  		VhostUserVringArea area;
>