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

["Liu, Changpeng" <changpeng.liu@intel.com>]

> -----Original Message-----
> From: Ilya Maximets [mailto:i.maximets@samsung.com]
> Sent: Monday, February 25, 2019 9:20 PM
> To: Liu, Changpeng <changpeng.liu@intel.com>; dev@dpdk.org
> Cc: Stojaczyk, Dariusz <dariusz.stojaczyk@intel.com>;
> maxime.coquelin@redhat.com; Bie, Tiwei <tiwei.bie@intel.com>; Wang,
> Zhihong <zhihong.wang@intel.com>; Jason Wang <jasowang@redhat.com>
> Subject: Re: vhost: add virtio configuration space access socket messages
> 
> 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 ?
QEMU will not send the messages if VHOST_USER_PROTOCOL_F_CONFIG wasn't enabled.
> 
> 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)'.
Yeah, can be changed to 0 here, QEMU can process it.
> 
> 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;
> >