Date:   Fri, 15 Jan 2021 17:51:57 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Ido Schimmel <idosch@...sch.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        jacob.e.keller@...el.com, roopa@...dia.com, mlxsw@...dia.com
Subject: Re: [patch net-next RFC 02/10] devlink: implement line card
 provisioning

Fri, Jan 15, 2021 at 05:03:19PM CET, idosch@...sch.org wrote:
>On Wed, Jan 13, 2021 at 01:12:14PM +0100, Jiri Pirko wrote:
>> From: Jiri Pirko <jiri@...dia.com>
>> 
>> In order to be able to configure all needed stuff on a port/netdevice
>> of a line card without the line card being present, introduce line card
>> provisioning. Basically provisioning will create a placeholder for
>> instances (ports/netdevices) for a line card type.
>> 
>> Allow the user to query the supported line card types over line card
>> get command. Then implement two netlink commands to allow user to
>> provision/unprovision the line card with selected line card type.
>> 
>> On the driver API side, add provision/unprovision ops and supported
>> types array to be advertised. Upon provision op call, the driver should
>> take care of creating the instances for the particular line card type.
>> Introduce provision_set/clear() functions to be called by the driver
>> once the provisioning/unprovisioning is done on its side.
>> 
>> Signed-off-by: Jiri Pirko <jiri@...dia.com>
>> ---
>>  include/net/devlink.h        |  31 +++++++-
>>  include/uapi/linux/devlink.h |  17 +++++
>>  net/core/devlink.c           | 141 ++++++++++++++++++++++++++++++++++-
>>  3 files changed, 185 insertions(+), 4 deletions(-)
>> 
>> diff --git a/include/net/devlink.h b/include/net/devlink.h
>> index 67c2547d5ef9..854abd53e9ea 100644
>> --- a/include/net/devlink.h
>> +++ b/include/net/devlink.h
>> @@ -139,10 +139,33 @@ struct devlink_port {
>>  	struct mutex reporters_lock; /* Protects reporter_list */
>>  };
>>  
>> +struct devlink_linecard_ops;
>> +
>>  struct devlink_linecard {
>>  	struct list_head list;
>>  	struct devlink *devlink;
>>  	unsigned int index;
>> +	const struct devlink_linecard_ops *ops;
>> +	void *priv;
>> +	enum devlink_linecard_state state;
>> +	const char *provisioned_type;
>> +};
>> +
>> +/**
>> + * struct devlink_linecard_ops - Linecard operations
>> + * @supported_types: array of supported types of linecards
>> + * @supported_types_count: number of elements in the array above
>> + * @provision: callback to provision the linecard slot with certain
>> + *	       type of linecard
>> + * @unprovision: callback to unprovision the linecard slot
>> + */
>> +struct devlink_linecard_ops {
>> +	const char **supported_types;
>> +	unsigned int supported_types_count;
>> +	int (*provision)(struct devlink_linecard *linecard, void *priv,
>> +			 u32 type_index, struct netlink_ext_ack *extack);
>> +	int (*unprovision)(struct devlink_linecard *linecard, void *priv,
>> +			   struct netlink_ext_ack *extack);
>>  };
>>  
>>  struct devlink_sb_pool_info {
>> @@ -1414,9 +1437,13 @@ void devlink_port_attrs_pci_pf_set(struct devlink_port *devlink_port, u32 contro
>>  				   u16 pf, bool external);
>>  void devlink_port_attrs_pci_vf_set(struct devlink_port *devlink_port, u32 controller,
>>  				   u16 pf, u16 vf, bool external);
>> -struct devlink_linecard *devlink_linecard_create(struct devlink *devlink,
>> -						 unsigned int linecard_index);
>> +struct devlink_linecard *
>> +devlink_linecard_create(struct devlink *devlink, unsigned int linecard_index,
>> +			const struct devlink_linecard_ops *ops, void *priv);
>>  void devlink_linecard_destroy(struct devlink_linecard *linecard);
>> +void devlink_linecard_provision_set(struct devlink_linecard *linecard,
>> +				    u32 type_index);
>> +void devlink_linecard_provision_clear(struct devlink_linecard *linecard);
>>  int devlink_sb_register(struct devlink *devlink, unsigned int sb_index,
>>  			u32 size, u16 ingress_pools_count,
>>  			u16 egress_pools_count, u16 ingress_tc_count,
>> diff --git a/include/uapi/linux/devlink.h b/include/uapi/linux/devlink.h
>> index e5ed0522591f..4111ddcc000b 100644
>> --- a/include/uapi/linux/devlink.h
>> +++ b/include/uapi/linux/devlink.h
>> @@ -131,6 +131,9 @@ enum devlink_command {
>>  	DEVLINK_CMD_LINECARD_NEW,
>>  	DEVLINK_CMD_LINECARD_DEL,
>>  
>> +	DEVLINK_CMD_LINECARD_PROVISION,
>> +	DEVLINK_CMD_LINECARD_UNPROVISION,
>
>I do not really see the point in these two commands. Better extend
>DEVLINK_CMD_LINECARD_SET to carry these attributes.

Yeah, I was thinking about that. Not sure it is correct though. This is
single purpose command. It really does not change "an attribute" as the
"_SET" commands are usually doing. Consider extension of "_SET" by other
attributes. Then it looks wrong.


>
>> +
>>  	/* add new commands above here */
>>  	__DEVLINK_CMD_MAX,
>>  	DEVLINK_CMD_MAX = __DEVLINK_CMD_MAX - 1
>> @@ -329,6 +332,17 @@ enum devlink_reload_limit {
>>  
>>  #define DEVLINK_RELOAD_LIMITS_VALID_MASK (_BITUL(__DEVLINK_RELOAD_LIMIT_MAX) - 1)
>>  
>> +enum devlink_linecard_state {
>> +	DEVLINK_LINECARD_STATE_UNSPEC,
>> +	DEVLINK_LINECARD_STATE_UNPROVISIONED,
>> +	DEVLINK_LINECARD_STATE_UNPROVISIONING,
>> +	DEVLINK_LINECARD_STATE_PROVISIONING,
>
>Can you explain why these two states are necessary? Any reason the
>provision operation can't be synchronous? This is somewhat explained in
>patch #8, but it should really be explained here. Changelog says:
>
>"To avoid deadlock and to mimic actual HW flow, use workqueue
>to add/del ports during provisioning as the port add/del calls
>devlink_port_register/unregister() which take devlink mutex."
>
>The deadlock is not really a reason to have these states.

It is, need to avoid recursice locking

>'DEVLINK_CMD_PORT_SPLIT' also calls devlink_port_register() /
>devlink_port_unregister() and the deadlock is solved by:
>
>'internal_flags = DEVLINK_NL_FLAG_NO_LOCK'

Yeah, however, there, the port_index is passed down to the driver, not
the actual object pointer. That's why it can be done like that.

>
>A hardware flow the requires it is something else...

Hardware flow in case of Spectrum is async too.


>
>> +	DEVLINK_LINECARD_STATE_PROVISIONED,
>> +
>> +	__DEVLINK_LINECARD_STATE_MAX,
>> +	DEVLINK_LINECARD_STATE_MAX = __DEVLINK_LINECARD_STATE_MAX - 1
>> +};
>> +
>>  enum devlink_attr {
>>  	/* don't change the order or add anything between, this is ABI! */
>>  	DEVLINK_ATTR_UNSPEC,
>> @@ -535,6 +549,9 @@ enum devlink_attr {
>>  	DEVLINK_ATTR_RELOAD_ACTION_STATS,       /* nested */
>>  
>>  	DEVLINK_ATTR_LINECARD_INDEX,		/* u32 */
>> +	DEVLINK_ATTR_LINECARD_STATE,		/* u8 */
>> +	DEVLINK_ATTR_LINECARD_TYPE,		/* string */
>> +	DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES,	/* nested */
>>  
>>  	/* add new attributes above here, update the policy in devlink.c */
>>  
>> diff --git a/net/core/devlink.c b/net/core/devlink.c
>> index 564e921133cf..434eecc310c3 100644
>> --- a/net/core/devlink.c
>> +++ b/net/core/devlink.c
>> @@ -1192,7 +1192,9 @@ static int devlink_nl_linecard_fill(struct sk_buff *msg,
>>  				    u32 seq, int flags,
>>  				    struct netlink_ext_ack *extack)
>>  {
>> +	struct nlattr *attr;
>>  	void *hdr;
>> +	int i;
>>  
>>  	hdr = genlmsg_put(msg, portid, seq, &devlink_nl_family, flags, cmd);
>>  	if (!hdr)
>> @@ -1202,6 +1204,22 @@ static int devlink_nl_linecard_fill(struct sk_buff *msg,
>>  		goto nla_put_failure;
>>  	if (nla_put_u32(msg, DEVLINK_ATTR_LINECARD_INDEX, linecard->index))
>>  		goto nla_put_failure;
>> +	if (nla_put_u8(msg, DEVLINK_ATTR_LINECARD_STATE, linecard->state))
>> +		goto nla_put_failure;
>> +	if (linecard->state >= DEVLINK_LINECARD_STATE_PROVISIONED &&
>
>This assumes that every state added after provisioned should report the
>type. Better to check for the specific states

Yes, that is correct assumption.


>
>> +	    nla_put_string(msg, DEVLINK_ATTR_LINECARD_TYPE,
>> +			   linecard->provisioned_type))
>> +		goto nla_put_failure;
>> +
>> +	attr = nla_nest_start(msg, DEVLINK_ATTR_LINECARD_SUPPORTED_TYPES);
>> +	if (!attr)
>> +		return -EMSGSIZE;
>> +	for (i = 0; i < linecard->ops->supported_types_count; i++) {
>> +		if (nla_put_string(msg, DEVLINK_ATTR_LINECARD_TYPE,
>> +				   linecard->ops->supported_types[i]))
>> +			goto nla_put_failure;
>> +	}
>> +	nla_nest_end(msg, attr);
>>  
>>  	genlmsg_end(msg, hdr);
>>  	return 0;
>> @@ -1300,6 +1318,68 @@ static int devlink_nl_cmd_linecard_get_dumpit(struct sk_buff *msg,
>>  	return msg->len;
>>  }
>>  
>> +static int devlink_nl_cmd_linecard_provision_doit(struct sk_buff *skb,
>> +						  struct genl_info *info)
>> +{
>> +	struct devlink_linecard *linecard = info->user_ptr[1];
>> +	const char *type;
>> +	int i;
>> +
>> +	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Linecard is currently being provisioned");
>> +		return -EBUSY;
>> +	}
>> +	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONING) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Linecard is currently being unprovisioned");
>> +		return -EBUSY;
>> +	}
>> +	if (linecard->state != DEVLINK_LINECARD_STATE_UNPROVISIONED) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Linecard already provisioned");
>> +		return -EBUSY;
>> +	}
>> +
>> +	if (!info->attrs[DEVLINK_ATTR_LINECARD_TYPE]) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Provision type not provided");
>> +		return -EINVAL;
>> +	}
>> +
>> +	type = nla_data(info->attrs[DEVLINK_ATTR_LINECARD_TYPE]);
>> +	for (i = 0; i < linecard->ops->supported_types_count; i++) {
>> +		if (!strcmp(linecard->ops->supported_types[i], type)) {
>> +			linecard->state = DEVLINK_LINECARD_STATE_PROVISIONING;
>> +			devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
>> +			return linecard->ops->provision(linecard,
>> +							linecard->priv, i,
>> +							info->extack);
>
>So if this fails user space will see 'provisioning' although nothing is
>being provisioned... Better to set the state and notify if this call did
>not fail

The driver is responsible to either call provision_set/provision_clear
helper. Note the async nature of this op.


>
>> +		}
>> +	}
>> +	NL_SET_ERR_MSG_MOD(info->extack, "Unsupported provision type provided");
>> +	return -EINVAL;
>> +}
>> +
>> +static int devlink_nl_cmd_linecard_unprovision_doit(struct sk_buff *skb,
>> +						    struct genl_info *info)
>> +{
>> +	struct devlink_linecard *linecard = info->user_ptr[1];
>> +
>> +	if (linecard->state == DEVLINK_LINECARD_STATE_PROVISIONING) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Linecard is currently being provisioned");
>> +		return -EBUSY;
>> +	}
>> +	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONING) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Linecard is currently being unprovisioned");
>> +		return -EBUSY;
>> +	}
>> +	if (linecard->state == DEVLINK_LINECARD_STATE_UNPROVISIONED) {
>> +		NL_SET_ERR_MSG_MOD(info->extack, "Linecard is not provisioned");
>> +		return -EOPNOTSUPP;
>> +	}
>> +	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONING;
>> +	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
>> +	return linecard->ops->unprovision(linecard, linecard->priv,
>> +					  info->extack);
>> +}
>> +
>>  static int devlink_nl_sb_fill(struct sk_buff *msg, struct devlink *devlink,
>>  			      struct devlink_sb *devlink_sb,
>>  			      enum devlink_command cmd, u32 portid,
>> @@ -7759,6 +7839,7 @@ static const struct nla_policy devlink_nl_policy[DEVLINK_ATTR_MAX + 1] = {
>>  							DEVLINK_RELOAD_ACTION_MAX),
>>  	[DEVLINK_ATTR_RELOAD_LIMITS] = NLA_POLICY_BITFIELD32(DEVLINK_RELOAD_LIMITS_VALID_MASK),
>>  	[DEVLINK_ATTR_LINECARD_INDEX] = { .type = NLA_U32 },
>> +	[DEVLINK_ATTR_LINECARD_TYPE] = { .type = NLA_NUL_STRING },
>>  };
>>  
>>  static const struct genl_small_ops devlink_nl_ops[] = {
>> @@ -7806,6 +7887,20 @@ static const struct genl_small_ops devlink_nl_ops[] = {
>>  		.internal_flags = DEVLINK_NL_FLAG_NEED_LINECARD,
>>  		/* can be retrieved by unprivileged users */
>>  	},
>> +	{
>> +		.cmd = DEVLINK_CMD_LINECARD_PROVISION,
>> +		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>> +		.doit = devlink_nl_cmd_linecard_provision_doit,
>> +		.flags = GENL_ADMIN_PERM,
>> +		.internal_flags = DEVLINK_NL_FLAG_NEED_LINECARD,
>> +	},
>> +	{
>> +		.cmd = DEVLINK_CMD_LINECARD_UNPROVISION,
>> +		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>> +		.doit = devlink_nl_cmd_linecard_unprovision_doit,
>> +		.flags = GENL_ADMIN_PERM,
>> +		.internal_flags = DEVLINK_NL_FLAG_NEED_LINECARD,
>> +	},
>>  	{
>>  		.cmd = DEVLINK_CMD_SB_GET,
>>  		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
>> @@ -8613,11 +8708,17 @@ static int __devlink_port_phys_port_name_get(struct devlink_port *devlink_port,
>>   *	Create devlink linecard instance with provided linecard index.
>>   *	Caller can use any indexing, even hw-related one.
>>   */
>> -struct devlink_linecard *devlink_linecard_create(struct devlink *devlink,
>> -						 unsigned int linecard_index)
>> +struct devlink_linecard *
>> +devlink_linecard_create(struct devlink *devlink, unsigned int linecard_index,
>> +			const struct devlink_linecard_ops *ops, void *priv)
>>  {
>>  	struct devlink_linecard *linecard;
>>  
>> +	if (WARN_ON(!ops || !ops->supported_types ||
>> +		    !ops->supported_types_count ||
>> +		    !ops->provision || !ops->unprovision))
>> +		return ERR_PTR(-EINVAL);
>> +
>>  	mutex_lock(&devlink->lock);
>>  	if (devlink_linecard_index_exists(devlink, linecard_index)) {
>>  		mutex_unlock(&devlink->lock);
>> @@ -8630,6 +8731,9 @@ struct devlink_linecard *devlink_linecard_create(struct devlink *devlink,
>>  
>>  	linecard->devlink = devlink;
>>  	linecard->index = linecard_index;
>> +	linecard->ops = ops;
>> +	linecard->priv = priv;
>> +	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
>>  	list_add_tail(&linecard->list, &devlink->linecard_list);
>>  	mutex_unlock(&devlink->lock);
>>  	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
>> @@ -8653,6 +8757,39 @@ void devlink_linecard_destroy(struct devlink_linecard *linecard)
>>  }
>>  EXPORT_SYMBOL_GPL(devlink_linecard_create);
>>  
>> +/**
>> + *	devlink_linecard_provision_set - Set provisioning on linecard
>
>'Set linecard as provisioned' maybe?

Sure, why not.


>
>> + *
>> + *	@devlink_linecard: devlink linecard
>> + *	@type_index: index of the linecard type (in array of types in ops)
>> + */
>> +void devlink_linecard_provision_set(struct devlink_linecard *linecard,
>> +				    u32 type_index)
>> +{
>> +	WARN_ON(type_index >= linecard->ops->supported_types_count);
>
>Wouldn't this explode below when you use the index to access the array?
>Maybe better to just warn and return

Okay.


>
>> +	mutex_lock(&linecard->devlink->lock);
>> +	linecard->state = DEVLINK_LINECARD_STATE_PROVISIONED;
>> +	linecard->provisioned_type = linecard->ops->supported_types[type_index];
>> +	mutex_unlock(&linecard->devlink->lock);
>> +	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
>> +}
>> +EXPORT_SYMBOL_GPL(devlink_linecard_provision_set);
>> +
>> +/**
>> + *	devlink_linecard_provision_clear - Clear provisioning on linecard
>
>'Set linecard as unprovisioned' maybe?

Sure, why not.


>
>> + *
>> + *	@devlink_linecard: devlink linecard
>> + */
>> +void devlink_linecard_provision_clear(struct devlink_linecard *linecard)
>> +{
>> +	mutex_lock(&linecard->devlink->lock);
>> +	linecard->state = DEVLINK_LINECARD_STATE_UNPROVISIONED;
>> +	linecard->provisioned_type = NULL;
>> +	mutex_unlock(&linecard->devlink->lock);
>> +	devlink_linecard_notify(linecard, DEVLINK_CMD_LINECARD_NEW);
>> +}
>> +EXPORT_SYMBOL_GPL(devlink_linecard_provision_clear);
>> +
>>  int devlink_sb_register(struct devlink *devlink, unsigned int sb_index,
>>  			u32 size, u16 ingress_pools_count,
>>  			u16 egress_pools_count, u16 ingress_tc_count,
>> -- 
>> 2.26.2
>> 

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