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

["Wodkowski, PawelX" <pawelx.wodkowski@intel.com>]

> -----Original Message-----
> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Wednesday, March 28, 2018 11:12 AM
> To: Kulasek, TomaszX <tomaszx.kulasek@intel.com>; yliu@fridaylinux.org
> Cc: Verkamp, Daniel <daniel.verkamp@intel.com>; Harris, James R
> <james.r.harris@intel.com>; Wodkowski, PawelX
> <pawelx.wodkowski@intel.com>; dev@dpdk.org; Liu, Changpeng
> <changpeng.liu@intel.com>; Tan, Jianfeng <jianfeng.tan@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v2] vhost: add virtio configuration space
> messages
> 
> 
> 
> 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.

What do mean by "external backends" ?
> 
> >   };
> >
> > 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];
> >