Re: [dpdk-dev] [PATCH v2] vhost: add virtio configuration space messages

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

On 03/27/2018 05:35 PM, Tomasz Kulasek wrote:
> This patch adds new vhost user messages GET_CONFIG and SET_CONFIG used
> for get/set virtio device's configuration space.
> 
> Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
> Signed-off-by: Tomasz Kulasek <tomaszx.kulasek@intel.com>
> ---
> Changes in v2:
>   - code cleanup
> 
>   lib/librte_vhost/rte_vhost.h  |  4 ++++
>   lib/librte_vhost/vhost_user.c | 22 ++++++++++++++++++++++
>   lib/librte_vhost/vhost_user.h | 16 ++++++++++++++++
>   3 files changed, 42 insertions(+)
> 
> diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
> index d332069..fe30518 100644
> --- a/lib/librte_vhost/rte_vhost.h
> +++ b/lib/librte_vhost/rte_vhost.h
> @@ -84,6 +84,10 @@ struct vhost_device_ops {
>   	int (*new_connection)(int vid);
>   	void (*destroy_connection)(int vid);
>   
> +	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);
> +
>   	void *reserved[2]; /**< Reserved for future extension */

You are breaking the ABI, as you grow the size of the ops struct.

Also, I'm wondering if we shouldn't have a different ops for external 
backends. Here these ops are more intended to the application, we could 
have a specific ops struct for external backends IMHO.

>   };
>   
> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
> index 90ed211..0ed6a5a 100644
> --- a/lib/librte_vhost/vhost_user.c
> +++ b/lib/librte_vhost/vhost_user.c
> @@ -50,6 +50,8 @@ static const char *vhost_message_str[VHOST_USER_MAX] = {
>   	[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",
>   };
>   
>   static uint64_t
> @@ -1355,6 +1357,7 @@ vhost_user_msg_handler(int vid, int fd)
>   	 * would cause a dead lock.
>   	 */
>   	switch (msg.request.master) {
> +	case VHOST_USER_SET_CONFIG:

It seems VHOST_USER_GET_CONFIG is missing here.

>   	case VHOST_USER_SET_FEATURES:
>   	case VHOST_USER_SET_PROTOCOL_FEATURES:
>   	case VHOST_USER_SET_OWNER:
> @@ -1380,6 +1383,25 @@ vhost_user_msg_handler(int vid, int fd)
>   	}
>   
>   	switch (msg.request.master) {
> +	case VHOST_USER_GET_CONFIG:
> +		if (dev->notify_ops->get_config(dev->vid,
Please check ->get_config is set before calling it.

> +				msg.payload.config.region,
> +				msg.payload.config.size) != 0) {
> +			msg.size = sizeof(uint64_t);
> +		}
> +		send_vhost_reply(fd, &msg);
> +		break;
> +	case VHOST_USER_SET_CONFIG:
> +		if ((dev->notify_ops->set_config(dev->vid,
Ditto.

> +				msg.payload.config.region,
> +				msg.payload.config.offset,
> +				msg.payload.config.size,
> +				msg.payload.config.flags)) != 0) {
> +			ret = 1;
> +		} else {
> +			ret = 0;
> +		}

ret = dev->notify_ops->set_config instead?
> +		break;
>   	case VHOST_USER_GET_FEATURES:
>   		msg.payload.u64 = vhost_user_get_features(dev);
>   		msg.size = sizeof(msg.payload.u64);
> diff --git a/lib/librte_vhost/vhost_user.h b/lib/librte_vhost/vhost_user.h
> index d4bd604..25cc026 100644
> --- a/lib/librte_vhost/vhost_user.h
> +++ b/lib/librte_vhost/vhost_user.h
> @@ -14,6 +14,11 @@
>   
>   #define VHOST_MEMORY_MAX_NREGIONS 8
>   
> +/*
> + * Maximum size of virtio device config space
> + */
> +#define VHOST_USER_MAX_CONFIG_SIZE 256
> +
>   #define VHOST_USER_PROTOCOL_F_MQ	0
>   #define VHOST_USER_PROTOCOL_F_LOG_SHMFD	1
>   #define VHOST_USER_PROTOCOL_F_RARP	2

Shouldn't there be a protocol feature associated to these new messages?
Else how QEMU knows the backend supports it or not?

I looked at QEMU code and indeed no protocol feature associated, that's
strange...

> @@ -52,12 +57,15 @@ typedef enum VhostUserRequest {
>   	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_MAX
>   } VhostUserRequest;
>   
>   typedef enum VhostUserSlaveRequest {
>   	VHOST_USER_SLAVE_NONE = 0,
>   	VHOST_USER_SLAVE_IOTLB_MSG = 1,
> +	VHOST_USER_SLAVE_CONFIG_CHANGE_MSG = 2,
>   	VHOST_USER_SLAVE_MAX
>   } VhostUserSlaveRequest;
>   
> @@ -79,6 +87,13 @@ typedef struct VhostUserLog {
>   	uint64_t mmap_offset;
>   } VhostUserLog;
>   
> +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 {
>   		VhostUserRequest master;
> @@ -98,6 +113,7 @@ typedef struct VhostUserMsg {
>   		struct vhost_vring_addr addr;
>   		VhostUserMemory memory;
>   		VhostUserLog    log;
> +		VhostUserConfig config;
>   		struct vhost_iotlb_msg iotlb;
>   	} payload;
>   	int fds[VHOST_MEMORY_MAX_NREGIONS];
>