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[213.179.129.39]) by smtp.gmail.com with ESMTPSA id c17-20020adffb11000000b0033725783839sm10019056wrr.110.2024.01.02.03.11.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Jan 2024 03:11:06 -0800 (PST) Date: Tue, 2 Jan 2024 12:11:05 +0100 From: Jiri Pirko To: David Wei Cc: Jakub Kicinski , Sabrina Dubroca , netdev@vger.kernel.org, "David S. Miller" , Eric Dumazet , Paolo Abeni Subject: Re: [PATCH net-next v5 2/5] netdevsim: allow two netdevsim ports to be connected Message-ID: References: <20231228014633.3256862-1-dw@davidwei.uk> <20231228014633.3256862-3-dw@davidwei.uk> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231228014633.3256862-3-dw@davidwei.uk> Thu, Dec 28, 2023 at 02:46:30AM CET, dw@davidwei.uk wrote: >Add a debugfs file in >/sys/kernel/debug/netdevsim/netdevsimN/ports/A/peer > >Writing "M B" to this file will link port A of netdevsim N with port B >of netdevsim M. Reading this file will return the linked netdevsim id >and port, if any. > >During nsim_dev_peer_write(), nsim_dev_list_lock prevents concurrent >modifications to nsim_dev and peer's devlink->lock prevents concurrent >modifications to the peer's port_list. rtnl_lock ensures netdevices do >not change during the critical section where a link is established. > >The lock order is consistent with other parts that touch netdevsim and >should not deadlock. > >During nsim_dev_peer_read(), RCU read critical section ensures valid >values even if stale. > >Signed-off-by: David Wei >--- > drivers/net/netdevsim/dev.c | 134 +++++++++++++++++++++++++++--- > drivers/net/netdevsim/netdev.c | 6 ++ > drivers/net/netdevsim/netdevsim.h | 1 + > 3 files changed, 128 insertions(+), 13 deletions(-) > >diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c >index 8d477aa99f94..6d5e4ce08dfd 100644 >--- a/drivers/net/netdevsim/dev.c >+++ b/drivers/net/netdevsim/dev.c >@@ -391,6 +391,124 @@ static const struct file_operations nsim_dev_rate_parent_fops = { > .owner = THIS_MODULE, > }; > >+static struct nsim_dev *nsim_dev_find_by_id(unsigned int id) >+{ >+ struct nsim_dev *dev; >+ >+ list_for_each_entry(dev, &nsim_dev_list, list) >+ if (dev->nsim_bus_dev->dev.id == id) >+ return dev; >+ >+ return NULL; >+} >+ >+static struct nsim_dev_port * >+__nsim_dev_port_lookup(struct nsim_dev *nsim_dev, enum nsim_dev_port_type type, >+ unsigned int port_index) >+{ >+ struct nsim_dev_port *nsim_dev_port; >+ >+ port_index = nsim_dev_port_index(type, port_index); >+ list_for_each_entry(nsim_dev_port, &nsim_dev->port_list, list) >+ if (nsim_dev_port->port_index == port_index) >+ return nsim_dev_port; >+ return NULL; >+} >+ >+static ssize_t nsim_dev_peer_read(struct file *file, char __user *data, >+ size_t count, loff_t *ppos) >+{ >+ struct nsim_dev_port *nsim_dev_port; >+ struct netdevsim *peer; >+ unsigned int id, port; >+ ssize_t ret = 0; >+ char buf[23]; >+ >+ nsim_dev_port = file->private_data; >+ rcu_read_lock(); >+ peer = rcu_dereference(nsim_dev_port->ns->peer); >+ if (!peer) { >+ rcu_read_unlock(); >+ return 0; >+ } >+ >+ id = peer->nsim_bus_dev->dev.id; >+ port = peer->nsim_dev_port->port_index; >+ ret = scnprintf(buf, sizeof(buf), "%u %u\n", id, port); >+ ret = simple_read_from_buffer(data, count, ppos, buf, ret); >+ >+ rcu_read_unlock(); >+ return ret; >+} >+ >+static ssize_t nsim_dev_peer_write(struct file *file, >+ const char __user *data, >+ size_t count, loff_t *ppos) >+{ >+ struct nsim_dev_port *nsim_dev_port, *peer_dev_port; >+ struct nsim_dev *peer_dev; >+ unsigned int id, port; >+ char buf[22]; >+ ssize_t ret; >+ >+ if (count >= sizeof(buf)) >+ return -ENOSPC; >+ >+ ret = copy_from_user(buf, data, count); >+ if (ret) >+ return -EFAULT; >+ buf[count] = '\0'; >+ >+ ret = sscanf(buf, "%u %u", &id, &port); >+ if (ret != 2) { >+ pr_err("Format is peer netdevsim \"id port\" (uint uint)\n"); >+ return -EINVAL; >+ } >+ >+ ret = -EINVAL; >+ mutex_lock(&nsim_dev_list_lock); >+ peer_dev = nsim_dev_find_by_id(id); >+ if (!peer_dev) { >+ pr_err("Peer netdevsim %u does not exist\n", id); >+ goto out_mutex; >+ } >+ >+ devl_lock(priv_to_devlink(peer_dev)); Why exactly do you take devlink instance mutex of the peer here? >+ rtnl_lock(); >+ nsim_dev_port = file->private_data; >+ peer_dev_port = __nsim_dev_port_lookup(peer_dev, NSIM_DEV_PORT_TYPE_PF, >+ port); >+ if (!peer_dev_port) { >+ pr_err("Peer netdevsim %u port %u does not exist\n", id, port); >+ goto out_devl; >+ } >+ >+ if (nsim_dev_port == peer_dev_port) { >+ pr_err("Cannot link netdevsim to itself\n"); >+ goto out_devl; >+ } >+ >+ rcu_assign_pointer(nsim_dev_port->ns->peer, peer_dev_port->ns); >+ rcu_assign_pointer(peer_dev_port->ns->peer, nsim_dev_port->ns); >+ ret = count; >+ >+out_devl: >+ rtnl_unlock(); >+ devl_unlock(priv_to_devlink(peer_dev)); >+out_mutex: >+ mutex_unlock(&nsim_dev_list_lock); >+ >+ return ret; >+} >+ >+static const struct file_operations nsim_dev_peer_fops = { >+ .open = simple_open, >+ .read = nsim_dev_peer_read, >+ .write = nsim_dev_peer_write, >+ .llseek = generic_file_llseek, >+ .owner = THIS_MODULE, >+}; >+ > static int nsim_dev_port_debugfs_init(struct nsim_dev *nsim_dev, > struct nsim_dev_port *nsim_dev_port) > { >@@ -421,6 +539,9 @@ static int nsim_dev_port_debugfs_init(struct nsim_dev *nsim_dev, > } > debugfs_create_symlink("dev", nsim_dev_port->ddir, dev_link_name); > >+ debugfs_create_file("peer", 0600, nsim_dev_port->ddir, >+ nsim_dev_port, &nsim_dev_peer_fops); >+ > return 0; > } > >@@ -1704,19 +1825,6 @@ void nsim_drv_remove(struct nsim_bus_dev *nsim_bus_dev) > dev_set_drvdata(&nsim_bus_dev->dev, NULL); > } > >-static struct nsim_dev_port * >-__nsim_dev_port_lookup(struct nsim_dev *nsim_dev, enum nsim_dev_port_type type, >- unsigned int port_index) >-{ >- struct nsim_dev_port *nsim_dev_port; >- >- port_index = nsim_dev_port_index(type, port_index); >- list_for_each_entry(nsim_dev_port, &nsim_dev->port_list, list) >- if (nsim_dev_port->port_index == port_index) >- return nsim_dev_port; >- return NULL; >-} >- > int nsim_drv_port_add(struct nsim_bus_dev *nsim_bus_dev, enum nsim_dev_port_type type, > unsigned int port_index) > { >diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c >index aecaf5f44374..434322f6a565 100644 >--- a/drivers/net/netdevsim/netdev.c >+++ b/drivers/net/netdevsim/netdev.c >@@ -388,6 +388,7 @@ nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port) > ns->nsim_dev = nsim_dev; > ns->nsim_dev_port = nsim_dev_port; > ns->nsim_bus_dev = nsim_dev->nsim_bus_dev; >+ RCU_INIT_POINTER(ns->peer, NULL); > SET_NETDEV_DEV(dev, &ns->nsim_bus_dev->dev); > SET_NETDEV_DEVLINK_PORT(dev, &nsim_dev_port->devlink_port); > nsim_ethtool_init(ns); >@@ -407,8 +408,13 @@ nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port) > void nsim_destroy(struct netdevsim *ns) > { > struct net_device *dev = ns->netdev; >+ struct netdevsim *peer; > > rtnl_lock(); >+ peer = rtnl_dereference(ns->peer); >+ if (peer) >+ RCU_INIT_POINTER(peer->peer, NULL); >+ RCU_INIT_POINTER(ns->peer, NULL); > unregister_netdevice(dev); > if (nsim_dev_port_is_pf(ns->nsim_dev_port)) { > nsim_macsec_teardown(ns); >diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h >index babb61d7790b..24fc3fbda791 100644 >--- a/drivers/net/netdevsim/netdevsim.h >+++ b/drivers/net/netdevsim/netdevsim.h >@@ -125,6 +125,7 @@ struct netdevsim { > } udp_ports; > > struct nsim_ethtool ethtool; >+ struct netdevsim __rcu *peer; > }; > > struct netdevsim * >-- >2.39.3 >