[RFC PATCH net-next v5 4/9] net/smc: Introduce SMC-D loopback device

[Wen Gu]

This patch introduces a kind of loopback device for SMC-D, thus
enabling the SMC communication between two local sockets within
one OS instance.

The loopback device supports basic capabilities defined by SMC-D
options, and exposed as an SMC-D v2 device.

The GID of loopback device is random generated, CHID is 0xFFFF
and SEID is SMCD_DEFAULT_V2_SEID.

TODO:
- The hierarchy preference of coexistent SMC-D devices.

Signed-off-by: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
---
 include/net/smc.h      |   6 +
 net/smc/Makefile       |   2 +-
 net/smc/af_smc.c       |  12 +-
 net/smc/smc_cdc.c      |   9 +-
 net/smc/smc_cdc.h      |   1 +
 net/smc/smc_ism.h      |   2 +
 net/smc/smc_loopback.c | 406 +++++++++++++++++++++++++++++++++++++++++++++++++
 net/smc/smc_loopback.h |  51 +++++++
 8 files changed, 486 insertions(+), 3 deletions(-)
 create mode 100644 net/smc/smc_loopback.c
 create mode 100644 net/smc/smc_loopback.h

diff --git a/include/net/smc.h b/include/net/smc.h
index 26206d2..021ca42 100644
--- a/include/net/smc.h
+++ b/include/net/smc.h
@@ -41,6 +41,12 @@ struct smcd_dmb {
 	dma_addr_t dma_addr;
 };
 
+struct smcd_seid {
+	u8 seid_string[24];
+	u8 serial_number[4];
+	u8 type[4];
+};
+
 #define ISM_EVENT_DMB	0
 #define ISM_EVENT_GID	1
 #define ISM_EVENT_SWR	2
diff --git a/net/smc/Makefile b/net/smc/Makefile
index 875efcd..a8c3711 100644
--- a/net/smc/Makefile
+++ b/net/smc/Makefile
@@ -4,5 +4,5 @@ obj-$(CONFIG_SMC)	+= smc.o
 obj-$(CONFIG_SMC_DIAG)	+= smc_diag.o
 smc-y := af_smc.o smc_pnet.o smc_ib.o smc_clc.o smc_core.o smc_wr.o smc_llc.o
 smc-y += smc_cdc.o smc_tx.o smc_rx.o smc_close.o smc_ism.o smc_netlink.o smc_stats.o
-smc-y += smc_tracepoint.o
+smc-y += smc_tracepoint.o smc_loopback.o
 smc-$(CONFIG_SYSCTL) += smc_sysctl.o
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 50c38b6..3230309 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -53,6 +53,7 @@
 #include "smc_stats.h"
 #include "smc_tracepoint.h"
 #include "smc_sysctl.h"
+#include "smc_loopback.h"
 
 static DEFINE_MUTEX(smc_server_lgr_pending);	/* serialize link group
 						 * creation on server
@@ -3482,15 +3483,23 @@ static int __init smc_init(void)
 		goto out_sock;
 	}
 
+	rc = smc_loopback_init();
+	if (rc) {
+		pr_err("%s: smc_loopback_init fails with %d\n", __func__, rc);
+		goto out_ib;
+	}
+
 	rc = tcp_register_ulp(&smc_ulp_ops);
 	if (rc) {
 		pr_err("%s: tcp_ulp_register fails with %d\n", __func__, rc);
-		goto out_ib;
+		goto out_lo;
 	}
 
 	static_branch_enable(&tcp_have_smc);
 	return 0;
 
+out_lo:
+	smc_loopback_exit();
 out_ib:
 	smc_ib_unregister_client();
 out_sock:
@@ -3528,6 +3537,7 @@ static void __exit smc_exit(void)
 	tcp_unregister_ulp(&smc_ulp_ops);
 	sock_unregister(PF_SMC);
 	smc_core_exit();
+	smc_loopback_exit();
 	smc_ib_unregister_client();
 	smc_ism_exit();
 	destroy_workqueue(smc_close_wq);
diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 89105e9..2f79bac 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -410,7 +410,14 @@ static void smc_cdc_msg_recv(struct smc_sock *smc, struct smc_cdc_msg *cdc)
  */
 static void smcd_cdc_rx_tsklet(struct tasklet_struct *t)
 {
-	struct smc_connection *conn = from_tasklet(conn, t, rx_tsklet);
+	struct smc_connection *conn =
+		from_tasklet(conn, t, rx_tsklet);
+
+	smcd_cdc_rx_handler(conn);
+}
+
+void smcd_cdc_rx_handler(struct smc_connection *conn)
+{
 	struct smcd_cdc_msg *data_cdc;
 	struct smcd_cdc_msg cdc;
 	struct smc_sock *smc;
diff --git a/net/smc/smc_cdc.h b/net/smc/smc_cdc.h
index 696cc11..11559d4 100644
--- a/net/smc/smc_cdc.h
+++ b/net/smc/smc_cdc.h
@@ -301,5 +301,6 @@ int smcr_cdc_msg_send_validation(struct smc_connection *conn,
 				 struct smc_wr_buf *wr_buf);
 int smc_cdc_init(void) __init;
 void smcd_cdc_rx_init(struct smc_connection *conn);
+void smcd_cdc_rx_handler(struct smc_connection *conn);
 
 #endif /* SMC_CDC_H */
diff --git a/net/smc/smc_ism.h b/net/smc/smc_ism.h
index 14d2e77..d18c50a 100644
--- a/net/smc/smc_ism.h
+++ b/net/smc/smc_ism.h
@@ -15,6 +15,8 @@
 
 #include "smc.h"
 
+#define S390_ISM_IDENT_MASK 0x00FFFF
+
 struct smcd_dev_list {	/* List of SMCD devices */
 	struct list_head list;
 	struct mutex mutex;	/* Protects list of devices */
diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
new file mode 100644
index 0000000..4197201
--- /dev/null
+++ b/net/smc/smc_loopback.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Shared Memory Communications Direct over loopback device.
+ *
+ *  Provide a SMC-D loopback dummy device.
+ *
+ *  Copyright (c) 2022, Alibaba Inc.
+ *
+ *  Author: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
+ *          Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/types.h>
+#include <net/smc.h>
+
+#include "smc_cdc.h"
+#include "smc_ism.h"
+#include "smc_loopback.h"
+
+#define SMC_LO_SUPPORTS_V2	0x1 /* SMC-D loopback supports SMC-Dv2 */
+#define SMC_LO_DMA_ADDR_INVALID	(~(dma_addr_t)0)
+
+static const char smc_lo_dev_name[] = "smcd_loopback_dev";
+static struct smcd_seid SMC_LO_SEID = {
+	.seid_string = "IBM-SYSZ-ISMSEID00000000",
+	.serial_number = "0000",
+	.type = "0000",
+};
+
+static struct smc_lo_dev *lo_dev;
+
+static void smc_lo_create_seid(struct smcd_seid *seid)
+{
+#if IS_ENABLED(CONFIG_ISM)
+	struct cpuid id;
+	u16 ident_tail;
+	char tmp[5];
+
+	get_cpu_id(&id);
+	ident_tail = (u16)(id.ident & S390_ISM_IDENT_MASK);
+	snprintf(tmp, 5, "%04X", ident_tail);
+	memcpy(&seid->serial_number, tmp, 4);
+	snprintf(tmp, 5, "%04X", id.machine);
+	memcpy(&seid->type, tmp, 4);
+#endif
+}
+
+static void smc_lo_generate_id(struct smc_lo_dev *ldev)
+{
+	/* Note that local GID of loopback device is random generated,
+	 * so there is a very little possibility of collision. The
+	 * collision may cause a mistaken belief that two sides are on
+	 * the same OS instance and loopback device can be used to
+	 * communicate with each other.
+	 *
+	 * But here is a relief that when choosing loopback device in
+	 * CLC handshake, local sndbuf will be attached to peer RMB (DMB),
+	 * which involves another 64-bits rtoken check.
+	 *
+	 * Therefore, the probability of mistakenly believing loopback
+	 * can be used is equivalent to the collision probability of
+	 * 128-bits random numbers (64-bits GID and 64-bits rtoken).
+	 */
+	get_random_bytes(&ldev->local_gid, sizeof(ldev->local_gid));
+	ldev->chid = SMC_LO_CHID;
+	smc_lo_create_seid(&SMC_LO_SEID);
+}
+
+static int smc_lo_query_rgid(struct smcd_dev *smcd, u64 rgid,
+			     u32 vid_valid, u32 vid)
+{
+	struct smc_lo_dev *ldev = smcd->priv;
+
+	/* rgid should equal to lgid in loopback */
+	if (!ldev || rgid != ldev->local_gid)
+		return -ENETUNREACH;
+	return 0;
+}
+
+static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
+			       void *client_priv)
+{
+	struct smc_lo_dmb_node *dmb_node, *tmp_node;
+	struct smc_lo_dev *ldev = smcd->priv;
+	int sba_idx, rc;
+
+	/* check space for new dmb */
+	for_each_clear_bit(sba_idx, ldev->sba_idx_mask, SMC_LODEV_MAX_DMBS) {
+		if (!test_and_set_bit(sba_idx, ldev->sba_idx_mask))
+			break;
+	}
+	if (sba_idx == SMC_LODEV_MAX_DMBS)
+		return -ENOSPC;
+
+	dmb_node = kzalloc(sizeof(*dmb_node), GFP_KERNEL);
+	if (!dmb_node) {
+		rc = -ENOMEM;
+		goto err_bit;
+	}
+
+	dmb_node->sba_idx = sba_idx;
+	dmb_node->cpu_addr = kzalloc(dmb->dmb_len, GFP_KERNEL |
+			     __GFP_NOWARN | __GFP_NORETRY |
+			     __GFP_NOMEMALLOC);
+	if (!dmb_node->cpu_addr) {
+		rc = -ENOMEM;
+		goto err_node;
+	}
+	dmb_node->len = dmb->dmb_len;
+	dmb_node->dma_addr = SMC_LO_DMA_ADDR_INVALID;
+
+again:
+	/* add new dmb into hash table */
+	get_random_bytes(&dmb_node->token, sizeof(dmb_node->token));
+	write_lock(&ldev->dmb_ht_lock);
+	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_node->token) {
+		/* make sure the tokens in the same OS are unique */
+		if (tmp_node->token == dmb_node->token) {
+			write_unlock(&ldev->dmb_ht_lock);
+			goto again;
+		}
+	}
+	hash_add(ldev->dmb_ht, &dmb_node->list, dmb_node->token);
+	write_unlock(&ldev->dmb_ht_lock);
+
+	dmb->sba_idx = dmb_node->sba_idx;
+	dmb->dmb_tok = dmb_node->token;
+	dmb->cpu_addr = dmb_node->cpu_addr;
+	dmb->dma_addr = dmb_node->dma_addr;
+	dmb->dmb_len = dmb_node->len;
+
+	return 0;
+
+err_node:
+	kfree(dmb_node);
+err_bit:
+	clear_bit(sba_idx, ldev->sba_idx_mask);
+	return rc;
+}
+
+static int smc_lo_unregister_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb)
+{
+	struct smc_lo_dmb_node *dmb_node = NULL, *tmp_node;
+	struct smc_lo_dev *ldev = smcd->priv;
+
+	/* remove dmb from hash table */
+	write_lock(&ldev->dmb_ht_lock);
+	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb->dmb_tok) {
+		if (tmp_node->token == dmb->dmb_tok) {
+			dmb_node = tmp_node;
+			break;
+		}
+	}
+	if (!dmb_node) {
+		write_unlock(&ldev->dmb_ht_lock);
+		return -EINVAL;
+	}
+	hash_del(&dmb_node->list);
+	write_unlock(&ldev->dmb_ht_lock);
+
+	clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
+	kfree(dmb_node->cpu_addr);
+	kfree(dmb_node);
+
+	return 0;
+}
+
+static int smc_lo_add_vlan_id(struct smcd_dev *smcd, u64 vlan_id)
+{
+	return -EOPNOTSUPP;
+}
+
+static int smc_lo_del_vlan_id(struct smcd_dev *smcd, u64 vlan_id)
+{
+	return -EOPNOTSUPP;
+}
+
+static int smc_lo_set_vlan_required(struct smcd_dev *smcd)
+{
+	return -EOPNOTSUPP;
+}
+
+static int smc_lo_reset_vlan_required(struct smcd_dev *smcd)
+{
+	return -EOPNOTSUPP;
+}
+
+static int smc_lo_signal_event(struct smcd_dev *dev, u64 rgid, u32 trigger_irq,
+			       u32 event_code, u64 info)
+{
+	return 0;
+}
+
+static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok, unsigned int idx,
+			    bool sf, unsigned int offset, void *data,
+			    unsigned int size)
+{
+	struct smc_lo_dmb_node *rmb_node = NULL, *tmp_node;
+	struct smc_lo_dev *ldev = smcd->priv;
+
+	read_lock(&ldev->dmb_ht_lock);
+	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, dmb_tok) {
+		if (tmp_node->token == dmb_tok) {
+			rmb_node = tmp_node;
+			break;
+		}
+	}
+	if (!rmb_node) {
+		read_unlock(&ldev->dmb_ht_lock);
+		return -EINVAL;
+	}
+	read_unlock(&ldev->dmb_ht_lock);
+
+	memcpy((char *)rmb_node->cpu_addr + offset, data, size);
+
+	if (sf) {
+		struct smc_connection *conn =
+			smcd->conn[rmb_node->sba_idx];
+
+		if (conn && !conn->killed)
+			smcd_cdc_rx_handler(conn);
+	}
+	return 0;
+}
+
+static int smc_lo_supports_v2(void)
+{
+	return SMC_LO_SUPPORTS_V2;
+}
+
+static u8 *smc_lo_get_system_eid(void)
+{
+	return SMC_LO_SEID.seid_string;
+}
+
+static u64 smc_lo_get_local_gid(struct smcd_dev *smcd)
+{
+	return ((struct smc_lo_dev *)smcd->priv)->local_gid;
+}
+
+static u16 smc_lo_get_chid(struct smcd_dev *smcd)
+{
+	return ((struct smc_lo_dev *)smcd->priv)->chid;
+}
+
+static struct device *smc_lo_get_dev(struct smcd_dev *smcd)
+{
+	return &((struct smc_lo_dev *)smcd->priv)->dev;
+}
+
+static const struct smcd_ops lo_ops = {
+	.query_remote_gid = smc_lo_query_rgid,
+	.register_dmb = smc_lo_register_dmb,
+	.unregister_dmb = smc_lo_unregister_dmb,
+	.add_vlan_id = smc_lo_add_vlan_id,
+	.del_vlan_id = smc_lo_del_vlan_id,
+	.set_vlan_required = smc_lo_set_vlan_required,
+	.reset_vlan_required = smc_lo_reset_vlan_required,
+	.signal_event = smc_lo_signal_event,
+	.move_data = smc_lo_move_data,
+	.supports_v2 = smc_lo_supports_v2,
+	.get_system_eid = smc_lo_get_system_eid,
+	.get_local_gid = smc_lo_get_local_gid,
+	.get_chid = smc_lo_get_chid,
+	.get_dev = smc_lo_get_dev,
+};
+
+static struct smcd_dev *smcd_lo_alloc_dev(const struct smcd_ops *ops,
+					  int max_dmbs)
+{
+	struct smcd_dev *smcd;
+
+	smcd = kzalloc(sizeof(*smcd), GFP_KERNEL);
+	if (!smcd)
+		return NULL;
+
+	smcd->conn = kcalloc(max_dmbs, sizeof(struct smc_connection *),
+			     GFP_KERNEL);
+	if (!smcd->conn)
+		goto out_smcd;
+
+	smcd->ops = ops;
+
+	spin_lock_init(&smcd->lock);
+	spin_lock_init(&smcd->lgr_lock);
+	INIT_LIST_HEAD(&smcd->vlan);
+	INIT_LIST_HEAD(&smcd->lgr_list);
+	init_waitqueue_head(&smcd->lgrs_deleted);
+	return smcd;
+
+out_smcd:
+	kfree(smcd);
+	return NULL;
+}
+
+static int smcd_lo_register_dev(struct smc_lo_dev *ldev)
+{
+	struct smcd_dev *smcd;
+
+	smcd = smcd_lo_alloc_dev(&lo_ops, SMC_LODEV_MAX_DMBS);
+	if (!smcd)
+		return -ENOMEM;
+
+	ldev->smcd = smcd;
+	smcd->priv = ldev;
+	smcd->parent_pci_dev = NULL;
+	mutex_lock(&smcd_dev_list.mutex);
+	smc_ism_check_v2_capable(smcd);
+	list_add(&smcd->list, &smcd_dev_list.list);
+	mutex_unlock(&smcd_dev_list.mutex);
+	pr_warn_ratelimited("smc: adding smcd device %s with pnetid %.16s%s\n",
+			    smc_lo_dev_name, smcd->pnetid,
+			    smcd->pnetid_by_user ? " (user defined)" : "");
+	return 0;
+}
+
+static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev)
+{
+	struct smcd_dev *smcd = ldev->smcd;
+
+	pr_warn_ratelimited("smc: removing smcd device %s\n",
+			    smc_lo_dev_name);
+	smcd->going_away = 1;
+	smc_smcd_terminate_all(smcd);
+	mutex_lock(&smcd_dev_list.mutex);
+	list_del_init(&smcd->list);
+	mutex_unlock(&smcd_dev_list.mutex);
+}
+
+static void smc_lo_dev_release(struct device *dev)
+{
+	struct smc_lo_dev *ldev =
+		container_of(dev, struct smc_lo_dev, dev);
+	struct smcd_dev *smcd = ldev->smcd;
+
+	kfree(smcd->conn);
+	kfree(smcd);
+	kfree(ldev);
+}
+
+static int smc_lo_dev_init(struct smc_lo_dev *ldev)
+{
+	smc_lo_generate_id(ldev);
+	rwlock_init(&ldev->dmb_ht_lock);
+	hash_init(ldev->dmb_ht);
+
+	return smcd_lo_register_dev(ldev);
+}
+
+static int smc_lo_dev_probe(void)
+{
+	struct smc_lo_dev *ldev;
+	int ret;
+
+	ldev = kzalloc(sizeof(*ldev), GFP_KERNEL);
+	if (!ldev)
+		return -ENOMEM;
+
+	ldev->dev.parent = NULL;
+	ldev->dev.release = smc_lo_dev_release;
+	device_initialize(&ldev->dev);
+	dev_set_name(&ldev->dev, smc_lo_dev_name);
+	ret = device_add(&ldev->dev);
+	if (ret)
+		goto free_dev;
+
+	ret = smc_lo_dev_init(ldev);
+	if (ret)
+		goto put_dev;
+
+	lo_dev = ldev; /* global loopback device */
+	return 0;
+
+put_dev:
+	device_del(&ldev->dev);
+free_dev:
+	kfree(ldev);
+	return ret;
+}
+
+static void smc_lo_dev_exit(struct smc_lo_dev *ldev)
+{
+	smcd_lo_unregister_dev(ldev);
+}
+
+static void smc_lo_dev_remove(void)
+{
+	if (!lo_dev)
+		return;
+
+	smc_lo_dev_exit(lo_dev);
+	device_del(&lo_dev->dev); /* device_add in smc_lo_dev_probe */
+	put_device(&lo_dev->dev); /* device_initialize in smc_lo_dev_probe */
+}
+
+int smc_loopback_init(void)
+{
+	return smc_lo_dev_probe();
+}
+
+void smc_loopback_exit(void)
+{
+	smc_lo_dev_remove();
+}
diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
new file mode 100644
index 0000000..9d34aba
--- /dev/null
+++ b/net/smc/smc_loopback.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Shared Memory Communications Direct over loopback device.
+ *
+ *  Provide a SMC-D loopback dummy device.
+ *
+ *  Copyright (c) 2022, Alibaba Inc.
+ *
+ *  Author: Wen Gu <guwen@xxxxxxxxxxxxxxxxx>
+ *          Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
+ *
+ */
+
+#ifndef _SMC_LOOPBACK_H
+#define _SMC_LOOPBACK_H
+
+#include <linux/types.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <net/smc.h>
+
+#include "smc_core.h"
+
+#define SMC_LO_CHID 0xFFFF
+#define SMC_LODEV_MAX_DMBS 5000
+#define SMC_LODEV_MAX_DMBS_BUCKETS 16
+
+struct smc_lo_dmb_node {
+	struct hlist_node list;
+	u64 token;
+	u32 len;
+	u32 sba_idx;
+	void *cpu_addr;
+	dma_addr_t dma_addr;
+};
+
+struct smc_lo_dev {
+	struct smcd_dev *smcd;
+	struct device dev;
+	u16 chid;
+	u64 local_gid;
+	DECLARE_BITMAP(sba_idx_mask, SMC_LODEV_MAX_DMBS);
+	rwlock_t dmb_ht_lock;
+	DECLARE_HASHTABLE(dmb_ht, SMC_LODEV_MAX_DMBS_BUCKETS);
+};
+
+int smc_loopback_init(void);
+void smc_loopback_exit(void);
+
+#endif /* _SMC_LOOPBACK_H */
-- 
1.8.3.1