[PATCH net-next v2 00/11] net/smc: SMC intra-OS shortcut with loopback-ism

[PATCH net-next v2 00/11] net/smc: SMC intra-OS shortcut with loopback-ism

[Wen Gu]

This patch set acts as the second part of the new version of [1] (The first
part can be referred from [2]), the updated things of this version are listed
at the end.

- Background

SMC-D is now used in IBM z with ISM function to optimize network interconnect
for intra-CPC communications. Inspired by this, we try to make SMC-D available
on the non-s390 architecture through a software-implemented Emulated-ISM device,
that is the loopback-ism device here, to accelerate inter-process or
inter-containers communication within the same OS instance.

- Design

This patch set includes 3 parts:

 - Patch #1-#2: some prepare work for loopback-ism.
 - Patch #3-#7: implement loopback-ism device. Noted that loopback-ism now
   serves only SMC and no userspace interface exposed.
 - Patch #10-#15: memory copy optimization for intra-OS scenario.

The loopback-ism device is designed as an ISMv2 device and not be limited to
a specific net namespace, ends of both inter-process connection (1/1' in diagram
below) or inter-container connection (2/2' in diagram below) can find the same
available loopback-ism and choose it during the CLC handshake.

 Container 1 (ns1)                              Container 2 (ns2)
 +-----------------------------------------+    +-------------------------+
 | +-------+      +-------+      +-------+ |    |        +-------+        |
 | | App A |      | App B |      | App C | |    |        | App D |<-+     |
 | +-------+      +---^---+      +-------+ |    |        +-------+  |(2') |
 |     |127.0.0.1 (1')|             |192.168.0.11       192.168.0.12|     |
 |  (1)|   +--------+ | +--------+  |(2)   |    | +--------+   +--------+ |
 |     `-->|   lo   |-` |  eth0  |<-`      |    | |   lo   |   |  eth0  | |
 +---------+--|---^-+---+-----|--+---------+    +-+--------+---+-^------+-+
              |   |           |                                  |
 Kernel       |   |           |                                  |
 +----+-------v---+-----------v----------------------------------+---+----+
 |    |                            TCP                               |    |
 |    |                                                              |    |
 |    +--------------------------------------------------------------+    |
 |                                                                        |
 |                           +--------------+                             |
 |                           | smc loopback |                             |
 +---------------------------+--------------+-----------------------------+

loopback-ism device creates DMBs (shared memory) for each connection peer.
Since data transfer occurs within the same kernel, the sndbuf of each peer
is only a descriptor and point to the same memory region as peer DMB, so that
the data copy from sndbuf to peer DMB can be avoided in loopback-ism case.

 Container 1 (ns1)                              Container 2 (ns2)
 +-----------------------------------------+    +-------------------------+
 | +-------+                               |    |        +-------+        |
 | | App C |-----+                         |    |        | App D |        |
 | +-------+     |                         |    |        +-^-----+        |
 |               |                         |    |          |              |
 |           (2) |                         |    |     (2') |              |
 |               |                         |    |          |              |
 +---------------|-------------------------+    +----------|--------------+
                 |                                         |
 Kernel          |                                         |
 +---------------|-----------------------------------------|--------------+
 | +--------+ +--v-----+                           +--------+ +--------+  |
 | |dmb_desc| |snd_desc|                           |dmb_desc| |snd_desc|  |
 | +-----|--+ +--|-----+                           +-----|--+ +--------+  |
 | +-----|--+    |                                 +-----|--+             |
 | | DMB C  |    +---------------------------------| DMB D  |             |
 | +--------+                                      +--------+             |
 |                                                                        |
 |                           +--------------+                             |
 |                           | smc loopback |                             |
 +---------------------------+--------------+-----------------------------+

- Benchmark Test

 * Test environments:
      - VM with Intel Xeon Platinum 8 core 2.50GHz, 16 GiB mem.
      - SMC sndbuf/DMB size 1MB.

 * Test object:
      - TCP: run on TCP loopback.
      - SMC lo: run on SMC loopback-ism.

1. ipc-benchmark (see [3])

 - ./<foo> -c 1000000 -s 100

                            TCP                  SMC-lo
Message
rate (msg/s)              79287                  148946(+87.86%)

2. sockperf

 - serv: <smc_run> taskset -c <cpu> sockperf sr --tcp
 - clnt: <smc_run> taskset -c <cpu> sockperf { tp | pp } --tcp --msg-size={ 64000 for tp | 14 for pp } -i 127.0.0.1 -t 30

                            TCP                  SMC-lo
Bandwidth(MBps)         5053.47                 8195.07(+62.17%)
Latency(us)               6.108                   3.404(-44.27%)

3. nginx/wrk

 - serv: <smc_run> nginx
 - clnt: <smc_run> wrk -t 8 -c 1000 -d 30 http://127.0.0.1:80

                           TCP                   SMC-lo
Requests/s           178187.56                247970.92(+39.16%)

4. redis-benchmark

 - serv: <smc_run> redis-server
 - clnt: <smc_run> redis-benchmark -h 127.0.0.1 -q -t set,get -n 400000 -c 200 -d 1024

                           TCP                   SMC-lo
GET(Requests/s)       89067.02                123877.36(+39.08%)
SET(Requests/s)       87700.07                131319.77(+49.73%)


Change log:

v2->v1:
- All the patches: changed the term virtual-ISM to Emulated-ISM as defined by SMCv2.1.
- Patch #3: optimized the description of SMC_LO config. Avoid exposing loopback-ism
  to sysfs and remove all the knobs until future definition clear.
- Patch #3: try to make lockdep happy by using read_lock_bh() in smc_lo_move_data().
- Patch #6: defaultly use physical contiguous DMB buffers.
- Patch #11: defaultly enable DMB no-copy for loopback-ism and free the DMB in
  unregister_dmb or detach_dmb when dmb_node->refcnt reaches 0, instead of using
  wait_event to keep waiting in unregister_dmb.

v1->RFC:
- Patch #9: merge rx_bytes and tx_bytes as xfer_bytes statistics:
  /sys/devices/virtual/smc/loopback-ism/xfer_bytes
- Patch #10: add support_dmb_nocopy operation to check if SMC-D device supports
  merging sndbuf with peer DMB.
- Patch #13 & #14: introduce loopback-ism device control of DMB memory type and
  control of whether to merge sndbuf and DMB. They can be respectively set by:
  /sys/devices/virtual/smc/loopback-ism/dmb_type
  /sys/devices/virtual/smc/loopback-ism/dmb_copy
  The motivation for these two control is that a performance bottleneck was
  found when using vzalloced DMB and sndbuf is merged with DMB, and there are
  many CPUs and CONFIG_HARDENED_USERCOPY is set [4]. The bottleneck is caused
  by the lock contention in vmap_area_lock [5] which is involved in memcpy_from_msg()
  or memcpy_to_msg(). Currently, Uladzislau Rezki is working on mitigating the
  vmap lock contention [6]. It has significant effects, but using virtual memory
  still has additional overhead compared to using physical memory.
  So this new version provides controls of dmb_type and dmb_copy to suit
  different scenarios.
- Some minor changes and comments improvements.

RFC->old version([1]):
Link: https://lore.kernel.org/netdev/1702214654-32069-1-git-send-email-guwen@linux.alibaba.com/
- Patch #1: improve the loopback-ism dump, it shows as follows now:
  # smcd d
  FID  Type  PCI-ID        PCHID  InUse  #LGs  PNET-ID
  0000 0     loopback-ism  ffff   No        0
- Patch #3: introduce the smc_ism_set_v2_capable() helper and set
  smc_ism_v2_capable when ISMv2 or virtual ISM is registered,
  regardless of whether there is already a device in smcd device list.
- Patch #3: loopback-ism will be added into /sys/devices/virtual/smc/loopback-ism/.
- Patch #8: introduce the runtime switch /sys/devices/virtual/smc/loopback-ism/active
  to activate or deactivate the loopback-ism.
- Patch #9: introduce the statistics of loopback-ism by
  /sys/devices/virtual/smc/loopback-ism/{{tx|rx}_tytes|dmbs_cnt}.
- Some minor changes and comments improvements.

[1] https://lore.kernel.org/netdev/1695568613-125057-1-git-send-email-guwen@linux.alibaba.com/
[2] https://lore.kernel.org/netdev/20231219142616.80697-1-guwen@linux.alibaba.com/
[3] https://github.com/goldsborough/ipc-bench
[4] https://lore.kernel.org/all/3189e342-c38f-6076-b730-19a6efd732a5@linux.alibaba.com/
[5] https://lore.kernel.org/all/238e63cd-e0e8-4fbf-852f-bc4d5bc35d5a@linux.alibaba.com/
[6] https://lore.kernel.org/all/20240102184633.748113-1-urezki@gmail.com/

Wen Gu (11):
  net/smc: adapt SMC-D device dump for Emulated-ISM
  net/smc: decouple ism_client from SMC-D DMB registration
  net/smc: introduce loopback-ism for SMC intra-OS shortcut
  net/smc: implement ID-related operations of loopback-ism
  net/smc: implement some unsupported operations of loopback-ism
  net/smc: implement DMB-related operations of loopback-ism
  net/smc: register loopback-ism into SMC-D device list
  net/smc: add operations to merge sndbuf with peer DMB
  net/smc: attach or detach ghost sndbuf to peer DMB
  net/smc: adapt cursor update when sndbuf and peer DMB are merged
  net/smc: implement DMB-merged operations of loopback-ism

 drivers/s390/net/ism_drv.c |   2 +-
 include/net/smc.h          |   7 +-
 net/smc/Kconfig            |  13 +
 net/smc/Makefile           |   2 +-
 net/smc/af_smc.c           |  28 ++-
 net/smc/smc_cdc.c          |  58 ++++-
 net/smc/smc_cdc.h          |   1 +
 net/smc/smc_core.c         |  61 ++++-
 net/smc/smc_core.h         |   1 +
 net/smc/smc_ism.c          |  71 +++++-
 net/smc/smc_ism.h          |   5 +
 net/smc/smc_loopback.c     | 469 +++++++++++++++++++++++++++++++++++++
 net/smc/smc_loopback.h     |  52 ++++
 13 files changed, 741 insertions(+), 29 deletions(-)
 create mode 100644 net/smc/smc_loopback.c
 create mode 100644 net/smc/smc_loopback.h

-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 01/11] net/smc: adapt SMC-D device dump for Emulated-ISM

[Wen Gu]

The introduction of Emulated-ISM requires adaptation of SMC-D device
dump. Software implemented non-PCI device (loopback-ism) should be
handled correctly and the CHID reserved for Emulated-ISM should be got
from smcd_ops interface instead of PCI information.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_ism.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
index ac88de2a06a0..b6eca4231913 100644
--- a/net/smc/smc_ism.c
+++ b/net/smc/smc_ism.c
@@ -252,12 +252,11 @@ static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
 	char smc_pnet[SMC_MAX_PNETID_LEN + 1];
 	struct smc_pci_dev smc_pci_dev;
 	struct nlattr *port_attrs;
+	struct device *device;
 	struct nlattr *attrs;
-	struct ism_dev *ism;
 	int use_cnt = 0;
 	void *nlh;
 
-	ism = smcd->priv;
 	nlh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
 			  &smc_gen_nl_family, NLM_F_MULTI,
 			  SMC_NETLINK_GET_DEV_SMCD);
@@ -272,7 +271,15 @@ static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
 	if (nla_put_u8(skb, SMC_NLA_DEV_IS_CRIT, use_cnt > 0))
 		goto errattr;
 	memset(&smc_pci_dev, 0, sizeof(smc_pci_dev));
-	smc_set_pci_values(to_pci_dev(ism->dev.parent), &smc_pci_dev);
+	device = smcd->ops->get_dev(smcd);
+	if (device->parent)
+		smc_set_pci_values(to_pci_dev(device->parent), &smc_pci_dev);
+	if (smc_ism_is_emulated(smcd)) {
+		smc_pci_dev.pci_pchid = smc_ism_get_chid(smcd);
+		if (!device->parent)
+			snprintf(smc_pci_dev.pci_id, sizeof(smc_pci_dev.pci_id),
+				 "%s", dev_name(device));
+	}
 	if (nla_put_u32(skb, SMC_NLA_DEV_PCI_FID, smc_pci_dev.pci_fid))
 		goto errattr;
 	if (nla_put_u16(skb, SMC_NLA_DEV_PCI_CHID, smc_pci_dev.pci_pchid))
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 02/11] net/smc: decouple ism_client from SMC-D DMB registration

[Wen Gu]

The struct 'ism_client' is specialized for s390 platform firmware ISM.
So replace it with 'void' to make SMCD DMB registration helper generic
for both Emulated-ISM and existing ISM.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 drivers/s390/net/ism_drv.c | 2 +-
 include/net/smc.h          | 4 ++--
 net/smc/smc_ism.c          | 7 ++-----
 3 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index 2c8e964425dc..9b2a52913e76 100644
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -726,7 +726,7 @@ static int smcd_query_rgid(struct smcd_dev *smcd, struct smcd_gid *rgid,
 }
 
 static int smcd_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
-			     struct ism_client *client)
+			     void *client)
 {
 	return ism_register_dmb(smcd->priv, (struct ism_dmb *)dmb, client);
 }
diff --git a/include/net/smc.h b/include/net/smc.h
index c9dcb30e3fd9..6273c3a8b24a 100644
--- a/include/net/smc.h
+++ b/include/net/smc.h
@@ -50,7 +50,6 @@ struct smcd_dmb {
 #define ISM_ERROR	0xFFFF
 
 struct smcd_dev;
-struct ism_client;
 
 struct smcd_gid {
 	u64	gid;
@@ -61,7 +60,7 @@ struct smcd_ops {
 	int (*query_remote_gid)(struct smcd_dev *dev, struct smcd_gid *rgid,
 				u32 vid_valid, u32 vid);
 	int (*register_dmb)(struct smcd_dev *dev, struct smcd_dmb *dmb,
-			    struct ism_client *client);
+			    void *client);
 	int (*unregister_dmb)(struct smcd_dev *dev, struct smcd_dmb *dmb);
 	int (*add_vlan_id)(struct smcd_dev *dev, u64 vlan_id);
 	int (*del_vlan_id)(struct smcd_dev *dev, u64 vlan_id);
@@ -81,6 +80,7 @@ struct smcd_ops {
 struct smcd_dev {
 	const struct smcd_ops *ops;
 	void *priv;
+	void *client;
 	struct list_head list;
 	spinlock_t lock;
 	struct smc_connection **conn;
diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
index b6eca4231913..26743a14cf27 100644
--- a/net/smc/smc_ism.c
+++ b/net/smc/smc_ism.c
@@ -222,7 +222,6 @@ int smc_ism_unregister_dmb(struct smcd_dev *smcd, struct smc_buf_desc *dmb_desc)
 int smc_ism_register_dmb(struct smc_link_group *lgr, int dmb_len,
 			 struct smc_buf_desc *dmb_desc)
 {
-#if IS_ENABLED(CONFIG_ISM)
 	struct smcd_dmb dmb;
 	int rc;
 
@@ -231,7 +230,7 @@ int smc_ism_register_dmb(struct smc_link_group *lgr, int dmb_len,
 	dmb.sba_idx = dmb_desc->sba_idx;
 	dmb.vlan_id = lgr->vlan_id;
 	dmb.rgid = lgr->peer_gid.gid;
-	rc = lgr->smcd->ops->register_dmb(lgr->smcd, &dmb, &smc_ism_client);
+	rc = lgr->smcd->ops->register_dmb(lgr->smcd, &dmb, lgr->smcd->client);
 	if (!rc) {
 		dmb_desc->sba_idx = dmb.sba_idx;
 		dmb_desc->token = dmb.dmb_tok;
@@ -240,9 +239,6 @@ int smc_ism_register_dmb(struct smc_link_group *lgr, int dmb_len,
 		dmb_desc->len = dmb.dmb_len;
 	}
 	return rc;
-#else
-	return 0;
-#endif
 }
 
 static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
@@ -453,6 +449,7 @@ static void smcd_register_dev(struct ism_dev *ism)
 	if (!smcd)
 		return;
 	smcd->priv = ism;
+	smcd->client = &smc_ism_client;
 	ism_set_priv(ism, &smc_ism_client, smcd);
 	if (smc_pnetid_by_dev_port(&ism->pdev->dev, 0, smcd->pnetid))
 		smc_pnetid_by_table_smcd(smcd);
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 03/11] net/smc: introduce loopback-ism for SMC intra-OS shortcut

[Wen Gu]

This introduces a kind of Emulated-ISM device named loopback-ism for
SMCv2.1. The loopback-ism device is currently exclusive for SMC usage,
and aims to provide a SMC shortcut for sockets within the same kernel,
leading to improved intra-OS traffic performance. Configuration of this
feature is managed through the config SMC_LO.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/Kconfig        |  13 ++++
 net/smc/Makefile       |   2 +-
 net/smc/af_smc.c       |  12 ++-
 net/smc/smc_loopback.c | 164 +++++++++++++++++++++++++++++++++++++++++
 net/smc/smc_loopback.h |  33 +++++++++
 5 files changed, 222 insertions(+), 2 deletions(-)
 create mode 100644 net/smc/smc_loopback.c
 create mode 100644 net/smc/smc_loopback.h

diff --git a/net/smc/Kconfig b/net/smc/Kconfig
index 746be3996768..2f1a8706a372 100644
--- a/net/smc/Kconfig
+++ b/net/smc/Kconfig
@@ -20,3 +20,16 @@ config SMC_DIAG
 	  smcss.
 
 	  if unsure, say Y.
+
+config SMC_LO
+	bool "SMC intra-OS shortcut with loopback-ism"
+	depends on SMC
+	default n
+	help
+	  SMC_LO enables the creation of an Emulated-ISM device named
+	  loopback-ism in SMC and the use of it for transferring data
+	  when communication occurs within the same OS. This helps in
+	  convenient testing of SMC-D since loopback-ism is independent
+	  of architecture or hardware.
+
+	  if unsure, say N.
diff --git a/net/smc/Makefile b/net/smc/Makefile
index 875efcd126a2..a8c37111abe1 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 4b52b3b159c0..751a8fdd6eb0 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
@@ -3557,15 +3558,23 @@ 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:
@@ -3603,6 +3612,7 @@ 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_loopback.c b/net/smc/smc_loopback.c
new file mode 100644
index 000000000000..e9170d86e58f
--- /dev/null
+++ b/net/smc/smc_loopback.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Shared Memory Communications Direct over loopback-ism device.
+ *
+ *  Provide a SMC-D loopback-ism device.
+ *
+ *  Copyright (c) 2024, Alibaba Inc.
+ *
+ *  Author: Wen Gu <guwen@linux.alibaba.com>
+ *          Tony Lu <tonylu@linux.alibaba.com>
+ *
+ */
+
+#include <linux/device.h>
+#include <linux/types.h>
+#include <net/smc.h>
+
+#include "smc_ism.h"
+#include "smc_loopback.h"
+
+#if IS_ENABLED(CONFIG_SMC_LO)
+static const char smc_lo_dev_name[] = "loopback-ism";
+static struct smc_lo_dev *lo_dev;
+
+static const struct smcd_ops lo_ops = {
+	.query_remote_gid	= NULL,
+	.register_dmb		= NULL,
+	.unregister_dmb		= NULL,
+	.add_vlan_id		= NULL,
+	.del_vlan_id		= NULL,
+	.set_vlan_required	= NULL,
+	.reset_vlan_required	= NULL,
+	.signal_event		= NULL,
+	.move_data		= NULL,
+	.supports_v2		= NULL,
+	.get_local_gid		= NULL,
+	.get_chid		= NULL,
+	.get_dev		= NULL,
+};
+
+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_LO_MAX_DMBS);
+	if (!smcd)
+		return -ENOMEM;
+	ldev->smcd = smcd;
+	smcd->priv = ldev;
+
+	/* TODO:
+	 * register loopback-ism to smcd_dev list.
+	 */
+	return 0;
+}
+
+static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev)
+{
+	struct smcd_dev *smcd = ldev->smcd;
+
+	/* TODO:
+	 * unregister loopback-ism from smcd_dev list.
+	 */
+	kfree(smcd->conn);
+	kfree(smcd);
+}
+
+static int smc_lo_dev_init(struct smc_lo_dev *ldev)
+{
+	return smcd_lo_register_dev(ldev);
+}
+
+static void smc_lo_dev_exit(struct smc_lo_dev *ldev)
+{
+	smcd_lo_unregister_dev(ldev);
+}
+
+static void smc_lo_dev_release(struct device *dev)
+{
+	struct smc_lo_dev *ldev =
+		container_of(dev, struct smc_lo_dev, dev);
+
+	kfree(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 = smc_lo_dev_init(ldev);
+	if (ret)
+		goto free_dev;
+
+	lo_dev = ldev; /* global loopback device */
+	return 0;
+
+free_dev:
+	put_device(&ldev->dev);
+	return ret;
+}
+
+static void smc_lo_dev_remove(void)
+{
+	if (!lo_dev)
+		return;
+
+	smc_lo_dev_exit(lo_dev);
+	put_device(&lo_dev->dev); /* device_initialize in smc_lo_dev_probe */
+}
+#endif
+
+int smc_loopback_init(void)
+{
+#if IS_ENABLED(CONFIG_SMC_LO)
+	return smc_lo_dev_probe();
+#else
+	return 0;
+#endif
+}
+
+void smc_loopback_exit(void)
+{
+#if IS_ENABLED(CONFIG_SMC_LO)
+	smc_lo_dev_remove();
+#endif
+}
diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
new file mode 100644
index 000000000000..9dd44d4c0ca3
--- /dev/null
+++ b/net/smc/smc_loopback.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  Shared Memory Communications Direct over loopback-ism device.
+ *
+ *  Provide a SMC-D loopback-ism device.
+ *
+ *  Copyright (c) 2024, Alibaba Inc.
+ *
+ *  Author: Wen Gu <guwen@linux.alibaba.com>
+ *          Tony Lu <tonylu@linux.alibaba.com>
+ *
+ */
+
+#ifndef _SMC_LOOPBACK_H
+#define _SMC_LOOPBACK_H
+
+#include <linux/device.h>
+#include <linux/err.h>
+#include <net/smc.h>
+
+#if IS_ENABLED(CONFIG_SMC_LO)
+#define SMC_LO_MAX_DMBS		5000
+
+struct smc_lo_dev {
+	struct smcd_dev *smcd;
+	struct device dev;
+};
+#endif
+
+int smc_loopback_init(void);
+void smc_loopback_exit(void);
+
+#endif /* _SMC_LOOPBACK_H */
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 04/11] net/smc: implement ID-related operations of loopback-ism

[Wen Gu]

This implements GID and CHID related operations of loopback-ism device.
loopback-ism acts as an ISMv2. It's GID is generated randomly by UUIDv4
algorithm and CHID is reserved 0xFFFF.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_loopback.c | 62 ++++++++++++++++++++++++++++++++++++++----
 net/smc/smc_loopback.h |  3 ++
 2 files changed, 60 insertions(+), 5 deletions(-)

diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
index e9170d86e58f..7656a2474500 100644
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -19,11 +19,62 @@
 #include "smc_loopback.h"
 
 #if IS_ENABLED(CONFIG_SMC_LO)
+#define SMC_LO_V2_CAPABLE	0x1 /* loopback-ism acts as ISMv2 */
+
 static const char smc_lo_dev_name[] = "loopback-ism";
 static struct smc_lo_dev *lo_dev;
 
+static void smc_lo_generate_id(struct smc_lo_dev *ldev)
+{
+	struct smcd_gid *lgid = &ldev->local_gid;
+	uuid_t uuid;
+
+	uuid_gen(&uuid);
+	memcpy(&lgid->gid, &uuid, sizeof(lgid->gid));
+	memcpy(&lgid->gid_ext, (u8 *)&uuid + sizeof(lgid->gid),
+	       sizeof(lgid->gid_ext));
+
+	ldev->chid = SMC_LO_CHID;
+}
+
+static int smc_lo_query_rgid(struct smcd_dev *smcd, struct smcd_gid *rgid,
+			     u32 vid_valid, u32 vid)
+{
+	struct smc_lo_dev *ldev = smcd->priv;
+
+	/* rgid should be the same as lgid */
+	if (!ldev || rgid->gid != ldev->local_gid.gid ||
+	    rgid->gid_ext != ldev->local_gid.gid_ext)
+		return -ENETUNREACH;
+	return 0;
+}
+
+static int smc_lo_supports_v2(void)
+{
+	return SMC_LO_V2_CAPABLE;
+}
+
+static void smc_lo_get_local_gid(struct smcd_dev *smcd,
+				 struct smcd_gid *smcd_gid)
+{
+	struct smc_lo_dev *ldev = smcd->priv;
+
+	smcd_gid->gid = ldev->local_gid.gid;
+	smcd_gid->gid_ext = ldev->local_gid.gid_ext;
+}
+
+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	= NULL,
+	.query_remote_gid = smc_lo_query_rgid,
 	.register_dmb		= NULL,
 	.unregister_dmb		= NULL,
 	.add_vlan_id		= NULL,
@@ -32,10 +83,10 @@ static const struct smcd_ops lo_ops = {
 	.reset_vlan_required	= NULL,
 	.signal_event		= NULL,
 	.move_data		= NULL,
-	.supports_v2		= NULL,
-	.get_local_gid		= NULL,
-	.get_chid		= NULL,
-	.get_dev		= NULL,
+	.supports_v2 = smc_lo_supports_v2,
+	.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,
@@ -95,6 +146,7 @@ static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev)
 
 static int smc_lo_dev_init(struct smc_lo_dev *ldev)
 {
+	smc_lo_generate_id(ldev);
 	return smcd_lo_register_dev(ldev);
 }
 
diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
index 9dd44d4c0ca3..55b41133a97f 100644
--- a/net/smc/smc_loopback.h
+++ b/net/smc/smc_loopback.h
@@ -20,10 +20,13 @@
 
 #if IS_ENABLED(CONFIG_SMC_LO)
 #define SMC_LO_MAX_DMBS		5000
+#define SMC_LO_CHID		0xFFFF
 
 struct smc_lo_dev {
 	struct smcd_dev *smcd;
 	struct device dev;
+	u16 chid;
+	struct smcd_gid local_gid;
 };
 #endif
 
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 05/11] net/smc: implement some unsupported operations of loopback-ism

[Wen Gu]

vlan operations are not supported currently since the need for vlan in
loopback-ism situation does not seem to be strong.

signal_event operation is not supported since no event now needs to be
processed by loopback-ism device.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_loopback.c | 36 +++++++++++++++++++++++++++++++-----
 1 file changed, 31 insertions(+), 5 deletions(-)

diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
index 7656a2474500..253128c77208 100644
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -49,6 +49,32 @@ static int smc_lo_query_rgid(struct smcd_dev *smcd, struct smcd_gid *rgid,
 	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, struct smcd_gid *rgid,
+			       u32 trigger_irq, u32 event_code, u64 info)
+{
+	return 0;
+}
+
 static int smc_lo_supports_v2(void)
 {
 	return SMC_LO_V2_CAPABLE;
@@ -77,11 +103,11 @@ static const struct smcd_ops lo_ops = {
 	.query_remote_gid = smc_lo_query_rgid,
 	.register_dmb		= NULL,
 	.unregister_dmb		= NULL,
-	.add_vlan_id		= NULL,
-	.del_vlan_id		= NULL,
-	.set_vlan_required	= NULL,
-	.reset_vlan_required	= NULL,
-	.signal_event		= NULL,
+	.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		= NULL,
 	.supports_v2 = smc_lo_supports_v2,
 	.get_local_gid = smc_lo_get_local_gid,
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 06/11] net/smc: implement DMB-related operations of loopback-ism

[Wen Gu]

This implements DMB (un)registration and data move operations of
loopback-ism device.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_cdc.c      |   6 ++
 net/smc/smc_cdc.h      |   1 +
 net/smc/smc_loopback.c | 131 ++++++++++++++++++++++++++++++++++++++++-
 net/smc/smc_loopback.h |  13 ++++
 4 files changed, 148 insertions(+), 3 deletions(-)

diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index 3c06625ceb20..c820ef197610 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -410,6 +410,12 @@ 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);
+
+	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 696cc11f2303..11559d4ebf2b 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_loopback.c b/net/smc/smc_loopback.c
index 253128c77208..39aa35bf38f5 100644
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -15,11 +15,13 @@
 #include <linux/types.h>
 #include <net/smc.h>
 
+#include "smc_cdc.h"
 #include "smc_ism.h"
 #include "smc_loopback.h"
 
 #if IS_ENABLED(CONFIG_SMC_LO)
 #define SMC_LO_V2_CAPABLE	0x1 /* loopback-ism acts as ISMv2 */
+#define SMC_DMA_ADDR_INVALID	(~(dma_addr_t)0)
 
 static const char smc_lo_dev_name[] = "loopback-ism";
 static struct smc_lo_dev *lo_dev;
@@ -49,6 +51,93 @@ static int smc_lo_query_rgid(struct smcd_dev *smcd, struct smcd_gid *rgid,
 	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_LO_MAX_DMBS) {
+		if (!test_and_set_bit(sba_idx, ldev->sba_idx_mask))
+			break;
+	}
+	if (sba_idx == SMC_LO_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->len = dmb->dmb_len;
+	dmb_node->cpu_addr = kzalloc(dmb_node->len, GFP_KERNEL |
+				     __GFP_NOWARN | __GFP_NORETRY |
+				     __GFP_NOMEMALLOC);
+	if (!dmb_node->cpu_addr) {
+		rc = -ENOMEM;
+		goto err_node;
+	}
+	dmb_node->dma_addr = SMC_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) {
+		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;
@@ -75,6 +164,40 @@ static int smc_lo_signal_event(struct smcd_dev *dev, struct smcd_gid *rgid,
 	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);
+		else
+			return -EPIPE;
+	}
+	return 0;
+}
+
 static int smc_lo_supports_v2(void)
 {
 	return SMC_LO_V2_CAPABLE;
@@ -101,14 +224,14 @@ static struct device *smc_lo_get_dev(struct smcd_dev *smcd)
 
 static const struct smcd_ops lo_ops = {
 	.query_remote_gid = smc_lo_query_rgid,
-	.register_dmb		= NULL,
-	.unregister_dmb		= NULL,
+	.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		= NULL,
+	.move_data = smc_lo_move_data,
 	.supports_v2 = smc_lo_supports_v2,
 	.get_local_gid = smc_lo_get_local_gid,
 	.get_chid = smc_lo_get_chid,
@@ -173,6 +296,8 @@ static void smcd_lo_unregister_dev(struct smc_lo_dev *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);
 }
 
diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
index 55b41133a97f..24ab9d747613 100644
--- a/net/smc/smc_loopback.h
+++ b/net/smc/smc_loopback.h
@@ -20,13 +20,26 @@
 
 #if IS_ENABLED(CONFIG_SMC_LO)
 #define SMC_LO_MAX_DMBS		5000
+#define SMC_LO_DMBS_HASH_BITS	12
 #define SMC_LO_CHID		0xFFFF
 
+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;
 	struct smcd_gid local_gid;
+	rwlock_t dmb_ht_lock;
+	DECLARE_BITMAP(sba_idx_mask, SMC_LO_MAX_DMBS);
+	DECLARE_HASHTABLE(dmb_ht, SMC_LO_DMBS_HASH_BITS);
 };
 #endif
 
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 07/11] net/smc: register loopback-ism into SMC-D device list

[Wen Gu]

After loopback-ism device gets ready, add it to the SMC-D device list as
an ISMv2 device.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_ism.c      | 11 +++++++----
 net/smc/smc_ism.h      |  1 +
 net/smc/smc_loopback.c | 20 +++++++++++++-------
 3 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
index 26743a14cf27..c50910300a03 100644
--- a/net/smc/smc_ism.c
+++ b/net/smc/smc_ism.c
@@ -91,6 +91,11 @@ bool smc_ism_is_v2_capable(void)
 	return smc_ism_v2_capable;
 }
 
+void smc_ism_set_v2_capable(void)
+{
+	smc_ism_v2_capable = true;
+}
+
 /* Set a connection using this DMBE. */
 void smc_ism_set_conn(struct smc_connection *conn)
 {
@@ -454,11 +459,9 @@ static void smcd_register_dev(struct ism_dev *ism)
 	if (smc_pnetid_by_dev_port(&ism->pdev->dev, 0, smcd->pnetid))
 		smc_pnetid_by_table_smcd(smcd);
 
+	if (smcd->ops->supports_v2())
+		smc_ism_set_v2_capable();
 	mutex_lock(&smcd_dev_list.mutex);
-	if (list_empty(&smcd_dev_list.list)) {
-		if (smcd->ops->supports_v2())
-			smc_ism_v2_capable = true;
-	}
 	/* sort list: devices without pnetid before devices with pnetid */
 	if (smcd->pnetid[0])
 		list_add_tail(&smcd->list, &smcd_dev_list.list);
diff --git a/net/smc/smc_ism.h b/net/smc/smc_ism.h
index 165cd013404b..2ea169c1301c 100644
--- a/net/smc/smc_ism.h
+++ b/net/smc/smc_ism.h
@@ -52,6 +52,7 @@ int smc_ism_signal_shutdown(struct smc_link_group *lgr);
 void smc_ism_get_system_eid(u8 **eid);
 u16 smc_ism_get_chid(struct smcd_dev *dev);
 bool smc_ism_is_v2_capable(void);
+void smc_ism_set_v2_capable(void);
 int smc_ism_init(void);
 void smc_ism_exit(void);
 int smcd_nl_get_device(struct sk_buff *skb, struct netlink_callback *cb);
diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
index 39aa35bf38f5..6828e0ad3e90 100644
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -275,10 +275,12 @@ static int smcd_lo_register_dev(struct smc_lo_dev *ldev)
 		return -ENOMEM;
 	ldev->smcd = smcd;
 	smcd->priv = ldev;
-
-	/* TODO:
-	 * register loopback-ism to smcd_dev list.
-	 */
+	smc_ism_set_v2_capable();
+	mutex_lock(&smcd_dev_list.mutex);
+	list_add(&smcd->list, &smcd_dev_list.list);
+	mutex_unlock(&smcd_dev_list.mutex);
+	pr_warn_ratelimited("smc: adding smcd device %s\n",
+			    smc_lo_dev_name);
 	return 0;
 }
 
@@ -286,9 +288,13 @@ static void smcd_lo_unregister_dev(struct smc_lo_dev *ldev)
 {
 	struct smcd_dev *smcd = ldev->smcd;
 
-	/* TODO:
-	 * unregister loopback-ism from smcd_dev list.
-	 */
+	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);
 	kfree(smcd->conn);
 	kfree(smcd);
 }
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 08/11] net/smc: add operations to merge sndbuf with peer DMB

[Wen Gu]

In some scenarios using Emulated-ISM device, sndbuf can share the same
physical memory region with peer DMB to avoid data copy from one side
to the other. In such case the sndbuf is only a descriptor that
describes the shared memory and does not actually occupy memory, it's
more like a ghost buffer.

      +----------+                     +----------+
      | socket A |                     | socket B |
      +----------+                     +----------+
            |                               |
       +--------+                       +--------+
       | sndbuf |                       |  DMB   |
       |  desc  |                       |  desc  |
       +--------+                       +--------+
            |                               |
            |                          +----v-----+
            +-------------------------->  memory  |
                                       +----------+

So here introduces three new SMC-D device operations to check if this
feature is supported by device, and to {attach|detach} ghost sndbuf to
peer DMB. For now only loopback-ism supports this.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 include/net/smc.h |  3 +++
 net/smc/smc_ism.c | 40 ++++++++++++++++++++++++++++++++++++++++
 net/smc/smc_ism.h |  4 ++++
 3 files changed, 47 insertions(+)

diff --git a/include/net/smc.h b/include/net/smc.h
index 6273c3a8b24a..01387631d8a6 100644
--- a/include/net/smc.h
+++ b/include/net/smc.h
@@ -62,6 +62,9 @@ struct smcd_ops {
 	int (*register_dmb)(struct smcd_dev *dev, struct smcd_dmb *dmb,
 			    void *client);
 	int (*unregister_dmb)(struct smcd_dev *dev, struct smcd_dmb *dmb);
+	int (*support_dmb_nocopy)(struct smcd_dev *dev);
+	int (*attach_dmb)(struct smcd_dev *dev, struct smcd_dmb *dmb);
+	int (*detach_dmb)(struct smcd_dev *dev, u64 token);
 	int (*add_vlan_id)(struct smcd_dev *dev, u64 vlan_id);
 	int (*del_vlan_id)(struct smcd_dev *dev, u64 vlan_id);
 	int (*set_vlan_required)(struct smcd_dev *dev);
diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
index c50910300a03..67ab9bce202a 100644
--- a/net/smc/smc_ism.c
+++ b/net/smc/smc_ism.c
@@ -246,6 +246,46 @@ int smc_ism_register_dmb(struct smc_link_group *lgr, int dmb_len,
 	return rc;
 }
 
+bool smc_ism_support_dmb_nocopy(struct smcd_dev *smcd)
+{
+	/* for now only loopback-ism supports
+	 * merging sndbuf with peer DMB to avoid
+	 * data copies between them.
+	 */
+	return (smcd->ops->support_dmb_nocopy &&
+		smcd->ops->support_dmb_nocopy(smcd));
+}
+
+int smc_ism_attach_dmb(struct smcd_dev *dev, u64 token,
+		       struct smc_buf_desc *dmb_desc)
+{
+	struct smcd_dmb dmb;
+	int rc = 0;
+
+	if (!dev->ops->attach_dmb)
+		return -EINVAL;
+
+	memset(&dmb, 0, sizeof(dmb));
+	dmb.dmb_tok = token;
+	rc = dev->ops->attach_dmb(dev, &dmb);
+	if (!rc) {
+		dmb_desc->sba_idx = dmb.sba_idx;
+		dmb_desc->token = dmb.dmb_tok;
+		dmb_desc->cpu_addr = dmb.cpu_addr;
+		dmb_desc->dma_addr = dmb.dma_addr;
+		dmb_desc->len = dmb.dmb_len;
+	}
+	return rc;
+}
+
+int smc_ism_detach_dmb(struct smcd_dev *dev, u64 token)
+{
+	if (!dev->ops->detach_dmb)
+		return -EINVAL;
+
+	return dev->ops->detach_dmb(dev, token);
+}
+
 static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
 				  struct sk_buff *skb,
 				  struct netlink_callback *cb)
diff --git a/net/smc/smc_ism.h b/net/smc/smc_ism.h
index 2ea169c1301c..83cf99265160 100644
--- a/net/smc/smc_ism.h
+++ b/net/smc/smc_ism.h
@@ -48,6 +48,10 @@ int smc_ism_put_vlan(struct smcd_dev *dev, unsigned short vlan_id);
 int smc_ism_register_dmb(struct smc_link_group *lgr, int buf_size,
 			 struct smc_buf_desc *dmb_desc);
 int smc_ism_unregister_dmb(struct smcd_dev *dev, struct smc_buf_desc *dmb_desc);
+bool smc_ism_support_dmb_nocopy(struct smcd_dev *smcd);
+int smc_ism_attach_dmb(struct smcd_dev *dev, u64 token,
+		       struct smc_buf_desc *dmb_desc);
+int smc_ism_detach_dmb(struct smcd_dev *dev, u64 token);
 int smc_ism_signal_shutdown(struct smc_link_group *lgr);
 void smc_ism_get_system_eid(u8 **eid);
 u16 smc_ism_get_chid(struct smcd_dev *dev);
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 09/11] net/smc: attach or detach ghost sndbuf to peer DMB

[Wen Gu]

The ghost sndbuf descriptor will be created and attached to peer DMB
once peer token is obtained and it will be detach and freed when the
connection is freed.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/af_smc.c   | 16 ++++++++++++
 net/smc/smc_core.c | 61 +++++++++++++++++++++++++++++++++++++++++++++-
 net/smc/smc_core.h |  1 +
 3 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 751a8fdd6eb0..fce7a5b2ce5c 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1438,6 +1438,14 @@ static int smc_connect_ism(struct smc_sock *smc,
 	}
 
 	smc_conn_save_peer_info(smc, aclc);
+
+	if (smc_ism_support_dmb_nocopy(smc->conn.lgr->smcd)) {
+		rc = smcd_buf_attach(smc);
+		if (rc) {
+			rc = SMC_CLC_DECL_MEM;	/* try to fallback */
+			goto connect_abort;
+		}
+	}
 	smc_close_init(smc);
 	smc_rx_init(smc);
 	smc_tx_init(smc);
@@ -2542,6 +2550,14 @@ static void smc_listen_work(struct work_struct *work)
 		mutex_unlock(&smc_server_lgr_pending);
 	}
 	smc_conn_save_peer_info(new_smc, cclc);
+
+	if (ini->is_smcd &&
+	    smc_ism_support_dmb_nocopy(new_smc->conn.lgr->smcd)) {
+		rc = smcd_buf_attach(new_smc);
+		if (rc)
+			goto out_decl;
+	}
+
 	smc_listen_out_connected(new_smc);
 	SMC_STAT_SERV_SUCC_INC(sock_net(newclcsock->sk), ini);
 	goto out_free;
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 9b84d5897aa5..fafdb97adfad 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1149,6 +1149,20 @@ static void smcr_buf_unuse(struct smc_buf_desc *buf_desc, bool is_rmb,
 	}
 }
 
+static void smcd_buf_detach(struct smc_connection *conn)
+{
+	struct smcd_dev *smcd = conn->lgr->smcd;
+	u64 peer_token = conn->peer_token;
+
+	if (!conn->sndbuf_desc)
+		return;
+
+	smc_ism_detach_dmb(smcd, peer_token);
+
+	kfree(conn->sndbuf_desc);
+	conn->sndbuf_desc = NULL;
+}
+
 static void smc_buf_unuse(struct smc_connection *conn,
 			  struct smc_link_group *lgr)
 {
@@ -1192,6 +1206,8 @@ void smc_conn_free(struct smc_connection *conn)
 	if (lgr->is_smcd) {
 		if (!list_empty(&lgr->list))
 			smc_ism_unset_conn(conn);
+		if (smc_ism_support_dmb_nocopy(lgr->smcd))
+			smcd_buf_detach(conn);
 		tasklet_kill(&conn->rx_tsklet);
 	} else {
 		smc_cdc_wait_pend_tx_wr(conn);
@@ -1445,6 +1461,8 @@ static void smc_conn_kill(struct smc_connection *conn, bool soft)
 	smc_sk_wake_ups(smc);
 	if (conn->lgr->is_smcd) {
 		smc_ism_unset_conn(conn);
+		if (smc_ism_support_dmb_nocopy(conn->lgr->smcd))
+			smcd_buf_detach(conn);
 		if (soft)
 			tasklet_kill(&conn->rx_tsklet);
 		else
@@ -2464,12 +2482,18 @@ int smc_buf_create(struct smc_sock *smc, bool is_smcd)
 	int rc;
 
 	/* create send buffer */
+	if (is_smcd &&
+	    smc_ism_support_dmb_nocopy(smc->conn.lgr->smcd))
+		goto create_rmb;
+
 	rc = __smc_buf_create(smc, is_smcd, false);
 	if (rc)
 		return rc;
+
+create_rmb:
 	/* create rmb */
 	rc = __smc_buf_create(smc, is_smcd, true);
-	if (rc) {
+	if (rc && smc->conn.sndbuf_desc) {
 		down_write(&smc->conn.lgr->sndbufs_lock);
 		list_del(&smc->conn.sndbuf_desc->list);
 		up_write(&smc->conn.lgr->sndbufs_lock);
@@ -2479,6 +2503,41 @@ int smc_buf_create(struct smc_sock *smc, bool is_smcd)
 	return rc;
 }
 
+int smcd_buf_attach(struct smc_sock *smc)
+{
+	struct smc_connection *conn = &smc->conn;
+	struct smcd_dev *smcd = conn->lgr->smcd;
+	u64 peer_token = conn->peer_token;
+	struct smc_buf_desc *buf_desc;
+	int rc;
+
+	buf_desc = kzalloc(sizeof(*buf_desc), GFP_KERNEL);
+	if (!buf_desc)
+		return -ENOMEM;
+
+	/* The ghost sndbuf_desc describes the same memory region as
+	 * peer RMB. Its lifecycle is consistent with the connection's
+	 * and it will be freed with the connections instead of the
+	 * link group.
+	 */
+	rc = smc_ism_attach_dmb(smcd, peer_token, buf_desc);
+	if (rc)
+		goto free;
+
+	smc->sk.sk_sndbuf = buf_desc->len;
+	buf_desc->cpu_addr =
+		(u8 *)buf_desc->cpu_addr + sizeof(struct smcd_cdc_msg);
+	buf_desc->len -= sizeof(struct smcd_cdc_msg);
+	conn->sndbuf_desc = buf_desc;
+	conn->sndbuf_desc->used = 1;
+	atomic_set(&conn->sndbuf_space, conn->sndbuf_desc->len);
+	return 0;
+
+free:
+	kfree(buf_desc);
+	return rc;
+}
+
 static inline int smc_rmb_reserve_rtoken_idx(struct smc_link_group *lgr)
 {
 	int i;
diff --git a/net/smc/smc_core.h b/net/smc/smc_core.h
index 1f175376037b..d93cf51dbd7c 100644
--- a/net/smc/smc_core.h
+++ b/net/smc/smc_core.h
@@ -557,6 +557,7 @@ void smc_smcd_terminate(struct smcd_dev *dev, struct smcd_gid *peer_gid,
 void smc_smcd_terminate_all(struct smcd_dev *dev);
 void smc_smcr_terminate_all(struct smc_ib_device *smcibdev);
 int smc_buf_create(struct smc_sock *smc, bool is_smcd);
+int smcd_buf_attach(struct smc_sock *smc);
 int smc_uncompress_bufsize(u8 compressed);
 int smc_rmb_rtoken_handling(struct smc_connection *conn, struct smc_link *link,
 			    struct smc_clc_msg_accept_confirm *clc);
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 10/11] net/smc: adapt cursor update when sndbuf and peer DMB are merged

[Wen Gu]

Since ghost sndbuf shares the same physical memory with peer DMB,
the cursor update processing needs to be adapted to ensure that the
data to be consumed won't be overwritten.

So in this case, the fin_curs and sndbuf_space that were originally
updated after sending the CDC message should be modified to not be
update until the peer updates cons_curs.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_cdc.c | 52 +++++++++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 11 deletions(-)

diff --git a/net/smc/smc_cdc.c b/net/smc/smc_cdc.c
index c820ef197610..e938fe3bcc7c 100644
--- a/net/smc/smc_cdc.c
+++ b/net/smc/smc_cdc.c
@@ -18,6 +18,7 @@
 #include "smc_tx.h"
 #include "smc_rx.h"
 #include "smc_close.h"
+#include "smc_ism.h"
 
 /********************************** send *************************************/
 
@@ -255,17 +256,25 @@ int smcd_cdc_msg_send(struct smc_connection *conn)
 		return rc;
 	smc_curs_copy(&conn->rx_curs_confirmed, &curs, conn);
 	conn->local_rx_ctrl.prod_flags.cons_curs_upd_req = 0;
-	/* Calculate transmitted data and increment free send buffer space */
-	diff = smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin,
-			     &conn->tx_curs_sent);
-	/* increased by confirmed number of bytes */
-	smp_mb__before_atomic();
-	atomic_add(diff, &conn->sndbuf_space);
-	/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
-	smp_mb__after_atomic();
-	smc_curs_copy(&conn->tx_curs_fin, &conn->tx_curs_sent, conn);
+	if (!smc_ism_support_dmb_nocopy(conn->lgr->smcd)) {
+		/* Ghost sndbuf shares the same memory region with
+		 * peer DMB, so don't update the tx_curs_fin and
+		 * sndbuf_space until peer has consumed the data.
+		 */
+		/* Calculate transmitted data and increment free
+		 * send buffer space
+		 */
+		diff = smc_curs_diff(conn->sndbuf_desc->len, &conn->tx_curs_fin,
+				     &conn->tx_curs_sent);
+		/* increased by confirmed number of bytes */
+		smp_mb__before_atomic();
+		atomic_add(diff, &conn->sndbuf_space);
+		/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
+		smp_mb__after_atomic();
+		smc_curs_copy(&conn->tx_curs_fin, &conn->tx_curs_sent, conn);
 
-	smc_tx_sndbuf_nonfull(smc);
+		smc_tx_sndbuf_nonfull(smc);
+	}
 	return rc;
 }
 
@@ -323,7 +332,7 @@ static void smc_cdc_msg_recv_action(struct smc_sock *smc,
 {
 	union smc_host_cursor cons_old, prod_old;
 	struct smc_connection *conn = &smc->conn;
-	int diff_cons, diff_prod;
+	int diff_cons, diff_prod, diff_tx;
 
 	smc_curs_copy(&prod_old, &conn->local_rx_ctrl.prod, conn);
 	smc_curs_copy(&cons_old, &conn->local_rx_ctrl.cons, conn);
@@ -339,6 +348,27 @@ static void smc_cdc_msg_recv_action(struct smc_sock *smc,
 		atomic_add(diff_cons, &conn->peer_rmbe_space);
 		/* guarantee 0 <= peer_rmbe_space <= peer_rmbe_size */
 		smp_mb__after_atomic();
+
+		if (conn->lgr->is_smcd &&
+		    smc_ism_support_dmb_nocopy(conn->lgr->smcd)) {
+			/* Ghost sndbuf shares the same memory region with
+			 * peer RMB, so update tx_curs_fin and sndbuf_space
+			 * when peer has consumed the data.
+			 */
+			/* calculate peer rmb consumed data */
+			diff_tx = smc_curs_diff(conn->sndbuf_desc->len,
+						&conn->tx_curs_fin,
+						&conn->local_rx_ctrl.cons);
+			/* increase local sndbuf space and fin_curs */
+			smp_mb__before_atomic();
+			atomic_add(diff_tx, &conn->sndbuf_space);
+			/* guarantee 0 <= sndbuf_space <= sndbuf_desc->len */
+			smp_mb__after_atomic();
+			smc_curs_copy(&conn->tx_curs_fin,
+				      &conn->local_rx_ctrl.cons, conn);
+
+			smc_tx_sndbuf_nonfull(smc);
+		}
 	}
 
 	diff_prod = smc_curs_diff(conn->rmb_desc->len, &prod_old,
-- 
2.32.0.3.g01195cf9f

[PATCH net-next v2 11/11] net/smc: implement DMB-merged operations of loopback-ism

[Wen Gu]

This implements operations related to merging sndbuf with peer DMB in
loopback-ism. The DMB won't be freed until no sndbuf is attached to it.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
---
 net/smc/smc_loopback.c | 136 +++++++++++++++++++++++++++++++++++------
 net/smc/smc_loopback.h |   3 +
 2 files changed, 119 insertions(+), 20 deletions(-)

diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
index 6828e0ad3e90..7e772f3772de 100644
--- a/net/smc/smc_loopback.c
+++ b/net/smc/smc_loopback.c
@@ -21,6 +21,7 @@
 
 #if IS_ENABLED(CONFIG_SMC_LO)
 #define SMC_LO_V2_CAPABLE	0x1 /* loopback-ism acts as ISMv2 */
+#define SMC_LO_SUPPORT_NOCOPY	0x1
 #define SMC_DMA_ADDR_INVALID	(~(dma_addr_t)0)
 
 static const char smc_lo_dev_name[] = "loopback-ism";
@@ -82,6 +83,7 @@ static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
 		goto err_node;
 	}
 	dmb_node->dma_addr = SMC_DMA_ADDR_INVALID;
+	refcount_set(&dmb_node->refcnt, 1);
 
 again:
 	/* add new dmb into hash table */
@@ -95,6 +97,7 @@ static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
 	}
 	hash_add(ldev->dmb_ht, &dmb_node->list, dmb_node->token);
 	write_unlock(&ldev->dmb_ht_lock);
+	atomic_inc(&ldev->dmb_cnt);
 
 	dmb->sba_idx = dmb_node->sba_idx;
 	dmb->dmb_tok = dmb_node->token;
@@ -111,13 +114,29 @@ static int smc_lo_register_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb,
 	return rc;
 }
 
+static void __smc_lo_unregister_dmb(struct smc_lo_dev *ldev,
+				    struct smc_lo_dmb_node *dmb_node)
+{
+	/* remove dmb from hash table */
+	write_lock(&ldev->dmb_ht_lock);
+	hash_del(&dmb_node->list);
+	write_unlock(&ldev->dmb_ht_lock);
+
+	clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
+	kvfree(dmb_node->cpu_addr);
+	kfree(dmb_node);
+
+	if (atomic_dec_and_test(&ldev->dmb_cnt))
+		wake_up(&ldev->ldev_release);
+}
+
 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);
+	/* find dmb from hash table */
+	read_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;
@@ -125,16 +144,76 @@ static int smc_lo_unregister_dmb(struct smcd_dev *smcd, struct smcd_dmb *dmb)
 		}
 	}
 	if (!dmb_node) {
-		write_unlock(&ldev->dmb_ht_lock);
+		read_unlock(&ldev->dmb_ht_lock);
 		return -EINVAL;
 	}
-	hash_del(&dmb_node->list);
-	write_unlock(&ldev->dmb_ht_lock);
+	read_unlock(&ldev->dmb_ht_lock);
 
-	clear_bit(dmb_node->sba_idx, ldev->sba_idx_mask);
-	kfree(dmb_node->cpu_addr);
-	kfree(dmb_node);
+	if (refcount_dec_and_test(&dmb_node->refcnt))
+		__smc_lo_unregister_dmb(ldev, dmb_node);
+	return 0;
+}
+
+static int smc_lo_support_dmb_nocopy(struct smcd_dev *smcd)
+{
+	return SMC_LO_SUPPORT_NOCOPY;
+}
+
+static int smc_lo_attach_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;
 
+	/* find dmb_node according to dmb->dmb_tok */
+	read_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) {
+		read_unlock(&ldev->dmb_ht_lock);
+		return -EINVAL;
+	}
+	read_unlock(&ldev->dmb_ht_lock);
+
+	if (!refcount_inc_not_zero(&dmb_node->refcnt))
+		/* the dmb is being unregistered, but has
+		 * not been removed from the hash table.
+		 */
+		return -EINVAL;
+
+	/* provide dmb information */
+	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;
+}
+
+static int smc_lo_detach_dmb(struct smcd_dev *smcd, u64 token)
+{
+	struct smc_lo_dmb_node *dmb_node = NULL, *tmp_node;
+	struct smc_lo_dev *ldev = smcd->priv;
+
+	/* find dmb_node according to dmb->dmb_tok */
+	read_lock(&ldev->dmb_ht_lock);
+	hash_for_each_possible(ldev->dmb_ht, tmp_node, list, token) {
+		if (tmp_node->token == token) {
+			dmb_node = tmp_node;
+			break;
+		}
+	}
+	if (!dmb_node) {
+		read_unlock(&ldev->dmb_ht_lock);
+		return -EINVAL;
+	}
+	read_unlock(&ldev->dmb_ht_lock);
+
+	if (refcount_dec_and_test(&dmb_node->refcnt))
+		__smc_lo_unregister_dmb(ldev, dmb_node);
 	return 0;
 }
 
@@ -170,8 +249,22 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
 {
 	struct smc_lo_dmb_node *rmb_node = NULL, *tmp_node;
 	struct smc_lo_dev *ldev = smcd->priv;
-
-	read_lock(&ldev->dmb_ht_lock);
+	struct smc_connection *conn;
+
+	if (!sf)
+		/* since sndbuf is merged with peer DMB, there is
+		 * no need to copy data from sndbuf to peer DMB.
+		 */
+		return 0;
+
+	/* read_lock_bh() is used here just to make lockdep
+	 * happy, because spin_(un)lock_bh(&conn->send_lock) wraps
+	 * smc_lo_move_data() and if we use read_lock() here, lockdep
+	 * will complain about SOFTIRQ-safe -> SOFTIRQ-unsafe lock
+	 * order detected, but in fact ldev->dmb_ht_lock will never
+	 * be held in bh context.
+	 */
+	read_lock_bh(&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;
@@ -182,19 +275,14 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
 		read_unlock(&ldev->dmb_ht_lock);
 		return -EINVAL;
 	}
-	read_unlock(&ldev->dmb_ht_lock);
+	read_unlock_bh(&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);
-		else
-			return -EPIPE;
-	}
+	conn = smcd->conn[rmb_node->sba_idx];
+	if (!conn || conn->killed)
+		return -EPIPE;
+	smcd_cdc_rx_handler(conn);
 	return 0;
 }
 
@@ -226,6 +314,9 @@ 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,
+	.support_dmb_nocopy = smc_lo_support_dmb_nocopy,
+	.attach_dmb = smc_lo_attach_dmb,
+	.detach_dmb = smc_lo_detach_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,
@@ -304,12 +395,17 @@ 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);
+	atomic_set(&ldev->dmb_cnt, 0);
+	init_waitqueue_head(&ldev->ldev_release);
+
 	return smcd_lo_register_dev(ldev);
 }
 
 static void smc_lo_dev_exit(struct smc_lo_dev *ldev)
 {
 	smcd_lo_unregister_dev(ldev);
+	if (atomic_read(&ldev->dmb_cnt))
+		wait_event(ldev->ldev_release, !atomic_read(&ldev->dmb_cnt));
 }
 
 static void smc_lo_dev_release(struct device *dev)
diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
index 24ab9d747613..9156a6c37e65 100644
--- a/net/smc/smc_loopback.h
+++ b/net/smc/smc_loopback.h
@@ -30,6 +30,7 @@ struct smc_lo_dmb_node {
 	u32 sba_idx;
 	void *cpu_addr;
 	dma_addr_t dma_addr;
+	refcount_t refcnt;
 };
 
 struct smc_lo_dev {
@@ -37,9 +38,11 @@ struct smc_lo_dev {
 	struct device dev;
 	u16 chid;
 	struct smcd_gid local_gid;
+	atomic_t dmb_cnt;
 	rwlock_t dmb_ht_lock;
 	DECLARE_BITMAP(sba_idx_mask, SMC_LO_MAX_DMBS);
 	DECLARE_HASHTABLE(dmb_ht, SMC_LO_DMBS_HASH_BITS);
+	wait_queue_head_t ldev_release;
 };
 #endif
 
-- 
2.32.0.3.g01195cf9f

Re: [PATCH net-next v2 00/11] net/smc: SMC intra-OS shortcut with loopback-ism

[Jan Karcher]

On 07/03/2024 10:55, Wen Gu wrote:
> This patch set acts as the second part of the new version of [1] (The first
> part can be referred from [2]), the updated things of this version are listed
> at the end.

Hi Wen Gu,

thanks for the updated patch. Please givr me some time to review and 
test the latest version.

Thanks
- Jan

> 
> - Background
> 
> SMC-D is now used in IBM z with ISM function to optimize network interconnect
> for intra-CPC communications. Inspired by this, we try to make SMC-D available
> on the non-s390 architecture through a software-implemented Emulated-ISM device,
> that is the loopback-ism device here, to accelerate inter-process or
> inter-containers communication within the same OS instance.
> 
> - Design
> 
> This patch set includes 3 parts:
> 
>   - Patch #1-#2: some prepare work for loopback-ism.
>   - Patch #3-#7: implement loopback-ism device. Noted that loopback-ism now
>     serves only SMC and no userspace interface exposed.
>   - Patch #10-#15: memory copy optimization for intra-OS scenario.
> 
> The loopback-ism device is designed as an ISMv2 device and not be limited to
> a specific net namespace, ends of both inter-process connection (1/1' in diagram
> below) or inter-container connection (2/2' in diagram below) can find the same
> available loopback-ism and choose it during the CLC handshake.
> 
>   Container 1 (ns1)                              Container 2 (ns2)
>   +-----------------------------------------+    +-------------------------+
>   | +-------+      +-------+      +-------+ |    |        +-------+        |
>   | | App A |      | App B |      | App C | |    |        | App D |<-+     |
>   | +-------+      +---^---+      +-------+ |    |        +-------+  |(2') |
>   |     |127.0.0.1 (1')|             |192.168.0.11       192.168.0.12|     |
>   |  (1)|   +--------+ | +--------+  |(2)   |    | +--------+   +--------+ |
>   |     `-->|   lo   |-` |  eth0  |<-`      |    | |   lo   |   |  eth0  | |
>   +---------+--|---^-+---+-----|--+---------+    +-+--------+---+-^------+-+
>                |   |           |                                  |
>   Kernel       |   |           |                                  |
>   +----+-------v---+-----------v----------------------------------+---+----+
>   |    |                            TCP                               |    |
>   |    |                                                              |    |
>   |    +--------------------------------------------------------------+    |
>   |                                                                        |
>   |                           +--------------+                             |
>   |                           | smc loopback |                             |
>   +---------------------------+--------------+-----------------------------+
> 
> loopback-ism device creates DMBs (shared memory) for each connection peer.
> Since data transfer occurs within the same kernel, the sndbuf of each peer
> is only a descriptor and point to the same memory region as peer DMB, so that
> the data copy from sndbuf to peer DMB can be avoided in loopback-ism case.
> 
>   Container 1 (ns1)                              Container 2 (ns2)
>   +-----------------------------------------+    +-------------------------+
>   | +-------+                               |    |        +-------+        |
>   | | App C |-----+                         |    |        | App D |        |
>   | +-------+     |                         |    |        +-^-----+        |
>   |               |                         |    |          |              |
>   |           (2) |                         |    |     (2') |              |
>   |               |                         |    |          |              |
>   +---------------|-------------------------+    +----------|--------------+
>                   |                                         |
>   Kernel          |                                         |
>   +---------------|-----------------------------------------|--------------+
>   | +--------+ +--v-----+                           +--------+ +--------+  |
>   | |dmb_desc| |snd_desc|                           |dmb_desc| |snd_desc|  |
>   | +-----|--+ +--|-----+                           +-----|--+ +--------+  |
>   | +-----|--+    |                                 +-----|--+             |
>   | | DMB C  |    +---------------------------------| DMB D  |             |
>   | +--------+                                      +--------+             |
>   |                                                                        |
>   |                           +--------------+                             |
>   |                           | smc loopback |                             |
>   +---------------------------+--------------+-----------------------------+
> 
> - Benchmark Test
> 
>   * Test environments:
>        - VM with Intel Xeon Platinum 8 core 2.50GHz, 16 GiB mem.
>        - SMC sndbuf/DMB size 1MB.
> 
>   * Test object:
>        - TCP: run on TCP loopback.
>        - SMC lo: run on SMC loopback-ism.
> 
> 1. ipc-benchmark (see [3])
> 
>   - ./<foo> -c 1000000 -s 100
> 
>                              TCP                  SMC-lo
> Message
> rate (msg/s)              79287                  148946(+87.86%)
> 
> 2. sockperf
> 
>   - serv: <smc_run> taskset -c <cpu> sockperf sr --tcp
>   - clnt: <smc_run> taskset -c <cpu> sockperf { tp | pp } --tcp --msg-size={ 64000 for tp | 14 for pp } -i 127.0.0.1 -t 30
> 
>                              TCP                  SMC-lo
> Bandwidth(MBps)         5053.47                 8195.07(+62.17%)
> Latency(us)               6.108                   3.404(-44.27%)
> 
> 3. nginx/wrk
> 
>   - serv: <smc_run> nginx
>   - clnt: <smc_run> wrk -t 8 -c 1000 -d 30 http://127.0.0.1:80
> 
>                             TCP                   SMC-lo
> Requests/s           178187.56                247970.92(+39.16%)
> 
> 4. redis-benchmark
> 
>   - serv: <smc_run> redis-server
>   - clnt: <smc_run> redis-benchmark -h 127.0.0.1 -q -t set,get -n 400000 -c 200 -d 1024
> 
>                             TCP                   SMC-lo
> GET(Requests/s)       89067.02                123877.36(+39.08%)
> SET(Requests/s)       87700.07                131319.77(+49.73%)
> 
> 
> Change log:
> 
> v2->v1:
> - All the patches: changed the term virtual-ISM to Emulated-ISM as defined by SMCv2.1.
> - Patch #3: optimized the description of SMC_LO config. Avoid exposing loopback-ism
>    to sysfs and remove all the knobs until future definition clear.
> - Patch #3: try to make lockdep happy by using read_lock_bh() in smc_lo_move_data().
> - Patch #6: defaultly use physical contiguous DMB buffers.
> - Patch #11: defaultly enable DMB no-copy for loopback-ism and free the DMB in
>    unregister_dmb or detach_dmb when dmb_node->refcnt reaches 0, instead of using
>    wait_event to keep waiting in unregister_dmb.
> 
> v1->RFC:
> - Patch #9: merge rx_bytes and tx_bytes as xfer_bytes statistics:
>    /sys/devices/virtual/smc/loopback-ism/xfer_bytes
> - Patch #10: add support_dmb_nocopy operation to check if SMC-D device supports
>    merging sndbuf with peer DMB.
> - Patch #13 & #14: introduce loopback-ism device control of DMB memory type and
>    control of whether to merge sndbuf and DMB. They can be respectively set by:
>    /sys/devices/virtual/smc/loopback-ism/dmb_type
>    /sys/devices/virtual/smc/loopback-ism/dmb_copy
>    The motivation for these two control is that a performance bottleneck was
>    found when using vzalloced DMB and sndbuf is merged with DMB, and there are
>    many CPUs and CONFIG_HARDENED_USERCOPY is set [4]. The bottleneck is caused
>    by the lock contention in vmap_area_lock [5] which is involved in memcpy_from_msg()
>    or memcpy_to_msg(). Currently, Uladzislau Rezki is working on mitigating the
>    vmap lock contention [6]. It has significant effects, but using virtual memory
>    still has additional overhead compared to using physical memory.
>    So this new version provides controls of dmb_type and dmb_copy to suit
>    different scenarios.
> - Some minor changes and comments improvements.
> 
> RFC->old version([1]):
> Link: https://lore.kernel.org/netdev/1702214654-32069-1-git-send-email-guwen@linux.alibaba.com/
> - Patch #1: improve the loopback-ism dump, it shows as follows now:
>    # smcd d
>    FID  Type  PCI-ID        PCHID  InUse  #LGs  PNET-ID
>    0000 0     loopback-ism  ffff   No        0
> - Patch #3: introduce the smc_ism_set_v2_capable() helper and set
>    smc_ism_v2_capable when ISMv2 or virtual ISM is registered,
>    regardless of whether there is already a device in smcd device list.
> - Patch #3: loopback-ism will be added into /sys/devices/virtual/smc/loopback-ism/.
> - Patch #8: introduce the runtime switch /sys/devices/virtual/smc/loopback-ism/active
>    to activate or deactivate the loopback-ism.
> - Patch #9: introduce the statistics of loopback-ism by
>    /sys/devices/virtual/smc/loopback-ism/{{tx|rx}_tytes|dmbs_cnt}.
> - Some minor changes and comments improvements.
> 
> [1] https://lore.kernel.org/netdev/1695568613-125057-1-git-send-email-guwen@linux.alibaba.com/
> [2] https://lore.kernel.org/netdev/20231219142616.80697-1-guwen@linux.alibaba.com/
> [3] https://github.com/goldsborough/ipc-bench
> [4] https://lore.kernel.org/all/3189e342-c38f-6076-b730-19a6efd732a5@linux.alibaba.com/
> [5] https://lore.kernel.org/all/238e63cd-e0e8-4fbf-852f-bc4d5bc35d5a@linux.alibaba.com/
> [6] https://lore.kernel.org/all/20240102184633.748113-1-urezki@gmail.com/
> 
> Wen Gu (11):
>    net/smc: adapt SMC-D device dump for Emulated-ISM
>    net/smc: decouple ism_client from SMC-D DMB registration
>    net/smc: introduce loopback-ism for SMC intra-OS shortcut
>    net/smc: implement ID-related operations of loopback-ism
>    net/smc: implement some unsupported operations of loopback-ism
>    net/smc: implement DMB-related operations of loopback-ism
>    net/smc: register loopback-ism into SMC-D device list
>    net/smc: add operations to merge sndbuf with peer DMB
>    net/smc: attach or detach ghost sndbuf to peer DMB
>    net/smc: adapt cursor update when sndbuf and peer DMB are merged
>    net/smc: implement DMB-merged operations of loopback-ism
> 
>   drivers/s390/net/ism_drv.c |   2 +-
>   include/net/smc.h          |   7 +-
>   net/smc/Kconfig            |  13 +
>   net/smc/Makefile           |   2 +-
>   net/smc/af_smc.c           |  28 ++-
>   net/smc/smc_cdc.c          |  58 ++++-
>   net/smc/smc_cdc.h          |   1 +
>   net/smc/smc_core.c         |  61 ++++-
>   net/smc/smc_core.h         |   1 +
>   net/smc/smc_ism.c          |  71 +++++-
>   net/smc/smc_ism.h          |   5 +
>   net/smc/smc_loopback.c     | 469 +++++++++++++++++++++++++++++++++++++
>   net/smc/smc_loopback.h     |  52 ++++
>   13 files changed, 741 insertions(+), 29 deletions(-)
>   create mode 100644 net/smc/smc_loopback.c
>   create mode 100644 net/smc/smc_loopback.h
> 

Re: [PATCH net-next v2 01/11] net/smc: adapt SMC-D device dump for Emulated-ISM

[Jan Karcher]

On 07/03/2024 10:55, Wen Gu wrote:
> The introduction of Emulated-ISM requires adaptation of SMC-D device
> dump. Software implemented non-PCI device (loopback-ism) should be
> handled correctly and the CHID reserved for Emulated-ISM should be got
> from smcd_ops interface instead of PCI information.
> 
> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
> ---
>   net/smc/smc_ism.c | 13 ++++++++++---
>   1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
> index ac88de2a06a0..b6eca4231913 100644
> --- a/net/smc/smc_ism.c
> +++ b/net/smc/smc_ism.c
> @@ -252,12 +252,11 @@ static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
>   	char smc_pnet[SMC_MAX_PNETID_LEN + 1];
>   	struct smc_pci_dev smc_pci_dev;
>   	struct nlattr *port_attrs;
> +	struct device *device;
>   	struct nlattr *attrs;
> -	struct ism_dev *ism;
>   	int use_cnt = 0;
>   	void *nlh;
>   
> -	ism = smcd->priv;
>   	nlh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
>   			  &smc_gen_nl_family, NLM_F_MULTI,
>   			  SMC_NETLINK_GET_DEV_SMCD);
> @@ -272,7 +271,15 @@ static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
>   	if (nla_put_u8(skb, SMC_NLA_DEV_IS_CRIT, use_cnt > 0))
>   		goto errattr;
>   	memset(&smc_pci_dev, 0, sizeof(smc_pci_dev));
> -	smc_set_pci_values(to_pci_dev(ism->dev.parent), &smc_pci_dev);
> +	device = smcd->ops->get_dev(smcd);
> +	if (device->parent)
> +		smc_set_pci_values(to_pci_dev(device->parent), &smc_pci_dev);
> +	if (smc_ism_is_emulated(smcd)) {

net/smc/smc_ism.c: In function ‘smc_nl_handle_smcd_dev’:
net/smc/smc_ism.c:318:13: error: implicit declaration of function 
‘smc_ism_is_emulated’ [-Werror=implicit-function-declaration]
   318 |         if (smc_ism_is_emulated(smcd)) {
       |             ^~~~~~~~~~~~~~~~~~~

> +		smc_pci_dev.pci_pchid = smc_ism_get_chid(smcd);
> +		if (!device->parent)
> +			snprintf(smc_pci_dev.pci_id, sizeof(smc_pci_dev.pci_id),
> +				 "%s", dev_name(device));
> +	}
>   	if (nla_put_u32(skb, SMC_NLA_DEV_PCI_FID, smc_pci_dev.pci_fid))
>   		goto errattr;
>   	if (nla_put_u16(skb, SMC_NLA_DEV_PCI_CHID, smc_pci_dev.pci_pchid))

Re: [PATCH net-next v2 01/11] net/smc: adapt SMC-D device dump for Emulated-ISM

[Wen Gu]

On 2024/3/8 20:27, Jan Karcher wrote:
> 
> 
> On 07/03/2024 10:55, Wen Gu wrote:
>> The introduction of Emulated-ISM requires adaptation of SMC-D device
>> dump. Software implemented non-PCI device (loopback-ism) should be
>> handled correctly and the CHID reserved for Emulated-ISM should be got
>> from smcd_ops interface instead of PCI information.
>>
>> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
>> ---
>>   net/smc/smc_ism.c | 13 ++++++++++---
>>   1 file changed, 10 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/smc/smc_ism.c b/net/smc/smc_ism.c
>> index ac88de2a06a0..b6eca4231913 100644
>> --- a/net/smc/smc_ism.c
>> +++ b/net/smc/smc_ism.c
>> @@ -252,12 +252,11 @@ static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
>>       char smc_pnet[SMC_MAX_PNETID_LEN + 1];
>>       struct smc_pci_dev smc_pci_dev;
>>       struct nlattr *port_attrs;
>> +    struct device *device;
>>       struct nlattr *attrs;
>> -    struct ism_dev *ism;
>>       int use_cnt = 0;
>>       void *nlh;
>> -    ism = smcd->priv;
>>       nlh = genlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
>>                 &smc_gen_nl_family, NLM_F_MULTI,
>>                 SMC_NETLINK_GET_DEV_SMCD);
>> @@ -272,7 +271,15 @@ static int smc_nl_handle_smcd_dev(struct smcd_dev *smcd,
>>       if (nla_put_u8(skb, SMC_NLA_DEV_IS_CRIT, use_cnt > 0))
>>           goto errattr;
>>       memset(&smc_pci_dev, 0, sizeof(smc_pci_dev));
>> -    smc_set_pci_values(to_pci_dev(ism->dev.parent), &smc_pci_dev);
>> +    device = smcd->ops->get_dev(smcd);
>> +    if (device->parent)
>> +        smc_set_pci_values(to_pci_dev(device->parent), &smc_pci_dev);
>> +    if (smc_ism_is_emulated(smcd)) {
> 
> net/smc/smc_ism.c: In function ‘smc_nl_handle_smcd_dev’:
> net/smc/smc_ism.c:318:13: error: implicit declaration of function ‘smc_ism_is_emulated’ 
> [-Werror=implicit-function-declaration]
>    318 |         if (smc_ism_is_emulated(smcd)) {
>        |             ^~~~~~~~~~~~~~~~~~~
> 

Hi Jan, the function smc_ism_is_emulated() is introduced by this merged patch:

b27696cd8fcc ("net/smc: change the term virtual ISM to Emulated-ISM")

Could you please check if your code base has this one?

Thanks!

>> +        smc_pci_dev.pci_pchid = smc_ism_get_chid(smcd);
>> +        if (!device->parent)
>> +            snprintf(smc_pci_dev.pci_id, sizeof(smc_pci_dev.pci_id),
>> +                 "%s", dev_name(device));
>> +    }
>>       if (nla_put_u32(skb, SMC_NLA_DEV_PCI_FID, smc_pci_dev.pci_fid))
>>           goto errattr;
>>       if (nla_put_u16(skb, SMC_NLA_DEV_PCI_CHID, smc_pci_dev.pci_pchid))

Re: [PATCH net-next v2 11/11] net/smc: implement DMB-merged operations of loopback-ism

[Jan Karcher]

On 07/03/2024 10:55, Wen Gu wrote:
> This implements operations related to merging sndbuf with peer DMB in
> loopback-ism. The DMB won't be freed until no sndbuf is attached to it.

Hi Wen Gu,

while I'm still reviewing let me drop a lockdep finding.

> 
> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
> ---
>   net/smc/smc_loopback.c | 136 +++++++++++++++++++++++++++++++++++------
>   net/smc/smc_loopback.h |   3 +
>   2 files changed, 119 insertions(+), 20 deletions(-)
> 
> diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
> index 6828e0ad3e90..7e772f3772de 100644
> --- a/net/smc/smc_loopback.c
> +++ b/net/smc/smc_loopback.c

[...]

>   
> @@ -170,8 +249,22 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
>   {
>   	struct smc_lo_dmb_node *rmb_node = NULL, *tmp_node;
>   	struct smc_lo_dev *ldev = smcd->priv;
> -
> -	read_lock(&ldev->dmb_ht_lock);
> +	struct smc_connection *conn;
> +
> +	if (!sf)
> +		/* since sndbuf is merged with peer DMB, there is
> +		 * no need to copy data from sndbuf to peer DMB.
> +		 */
> +		return 0;
> +
> +	/* read_lock_bh() is used here just to make lockdep
> +	 * happy, because spin_(un)lock_bh(&conn->send_lock) wraps
> +	 * smc_lo_move_data() and if we use read_lock() here, lockdep
> +	 * will complain about SOFTIRQ-safe -> SOFTIRQ-unsafe lock
> +	 * order detected, but in fact ldev->dmb_ht_lock will never
> +	 * be held in bh context.
> +	 */
> +	read_lock_bh(&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;
> @@ -182,19 +275,14 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
>   		read_unlock(&ldev->dmb_ht_lock);
>   		return -EINVAL;
>   	}
> -	read_unlock(&ldev->dmb_ht_lock);
> +	read_unlock_bh(&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);
> -		else
> -			return -EPIPE;
> -	}
> +	conn = smcd->conn[rmb_node->sba_idx];
> +	if (!conn || conn->killed)
> +		return -EPIPE;
> +	smcd_cdc_rx_handler(conn);

[ 2385.528515] ============================================
[ 2385.528517] WARNING: possible recursive locking detected
[ 2385.528519] 6.8.0-loopback_ism-g30af186e8a18-dirty #12 Not tainted
[ 2385.528521] --------------------------------------------
[ 2385.528522] smcapp/51326 is trying to acquire lock:
[ 2385.528524] 000000018707a128 (&smc->conn.send_lock){+...}-{2:2}, at: 
smc_tx_sndbuf_nonempty+0xba/0x1c0 [smc]
[ 2385.528552]
                but task is already holding lock:
[ 2385.528554] 0000000187078728 (&smc->conn.send_lock){+...}-{2:2}, at: 
smc_cdc_get_slot_and_msg_send+0x66/0xa0 [smc]
[ 2385.528568]
                other info that might help us debug this:
[ 2385.528570]  Possible unsafe locking scenario:

[ 2385.528572]        CPU0
[ 2385.528573]        ----
[ 2385.528574]   lock(&smc->conn.send_lock);
[ 2385.528576]   lock(&smc->conn.send_lock);
[ 2385.528579]
                 *** DEADLOCK ***

[ 2385.528580]  May be due to missing lock nesting notation

[ 2385.528582] 3 locks held by smcapp/51326:
[ 2385.528584]  #0: 0000000187078378 (sk_lock-AF_SMC){+.+.}-{0:0}, at: 
smc_recvmsg+0x3c/0x2b0 [smc]
[ 2385.528598]  #1: 0000000187078728 (&smc->conn.send_lock){+...}-{2:2}, 
at: smc_cdc_get_slot_and_msg_send+0x66/0xa0 [smc]
[ 2385.528613]  #2: 0000000187079ce8 (slock-AF_SMC){+...}-{2:2}, at: 
smc_cdc_msg_recv+0x56/0xe0 [smc]
[ 2385.528627]
                stack backtrace:
[ 2385.528660] CPU: 3 PID: 51326 Comm: smcapp Not tainted 
6.8.0-loopback_ism-g30af186e8a18-dirty #12
[ 2385.528663] Hardware name: IBM 3906 M04 704 (LPAR)
[ 2385.528664] Call Trace:
[ 2385.528666]  [<000000012db60788>] dump_stack_lvl+0x90/0x120
[ 2385.528671]  [<000000012cc6d088>] validate_chain+0x560/0x960
[ 2385.528677]  [<000000012cc6f644>] __lock_acquire+0x654/0xd58
[ 2385.528680]  [<000000012cc70a04>] lock_acquire.part.0+0xec/0x260
[ 2385.528683]  [<000000012cc70c24>] lock_acquire+0xac/0x170
[ 2385.528687]  [<000000012dba4ccc>] _raw_spin_lock_bh+0x5c/0xb0
[ 2385.528690]  [<000003ff80453b32>] smc_tx_sndbuf_nonempty+0xba/0x1c0 [smc]
[ 2385.528702]  [<000003ff8045428a>] smc_tx_pending+0x32/0x60 [smc]
[ 2385.528712]  [<000003ff80451f02>] smc_cdc_msg_recv_action+0x3c2/0x528 
[smc]
[ 2385.528723]  [<000003ff804520cc>] smc_cdc_msg_recv+0x64/0xe0 [smc]
[ 2385.528734]  [<000003ff80452a4c>] smcd_cdc_rx_handler+0x64/0x70 [smc]
[ 2385.528745]  [<000003ff80459f7e>] smc_lo_move_data+0xde/0x100 [smc]
[ 2385.528755]  [<000003ff804533e0>] smcd_tx_ism_write+0x68/0x90 [smc]
[ 2385.528766]  [<000003ff804528a4>] smcd_cdc_msg_send+0x74/0x118 [smc]
[ 2385.528776]  [<000003ff804529b8>] 
smc_cdc_get_slot_and_msg_send+0x70/0xa0 [smc]
[ 2385.528788]  [<000003ff804543ec>] smc_tx_consumer_update+0xe4/0x1b0 [smc]
[ 2385.528798]  [<000003ff8045458e>] smc_rx_update_consumer+0x86/0x170 [smc]
[ 2385.528809]  [<000003ff80455ba8>] smc_rx_recvmsg+0x3b8/0x6e8 [smc]
[ 2385.528820]  [<000003ff804388a4>] smc_recvmsg+0xdc/0x2b0 [smc]
[ 2385.528831]  [<000000012d8a6d58>] sock_recvmsg+0x70/0xb0
[ 2385.528837]  [<000000012d8aa0c8>] __sys_recvfrom+0xa8/0x128
[ 2385.528840]  [<000000012d8ab3ca>] __do_sys_socketcall+0x1ca/0x398
[ 2385.528844]  [<000000012db8d4c4>] __do_syscall+0x244/0x308
[ 2385.528847]  [<000000012dba6140>] system_call+0x70/0x98
[ 2385.528850] INFO: lockdep is turned off.


I did not investigate deeper, yet. Just an early heads up that there 
might be something broken.

Thank you
- Jan


>   	return 0;
>   }
>   
> @@ -226,6 +314,9 @@ 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,
> +	.support_dmb_nocopy = smc_lo_support_dmb_nocopy,
> +	.attach_dmb = smc_lo_attach_dmb,
> +	.detach_dmb = smc_lo_detach_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,
> @@ -304,12 +395,17 @@ 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);
> +	atomic_set(&ldev->dmb_cnt, 0);
> +	init_waitqueue_head(&ldev->ldev_release);
> +
>   	return smcd_lo_register_dev(ldev);
>   }
>   
>   static void smc_lo_dev_exit(struct smc_lo_dev *ldev)
>   {
>   	smcd_lo_unregister_dev(ldev);
> +	if (atomic_read(&ldev->dmb_cnt))
> +		wait_event(ldev->ldev_release, !atomic_read(&ldev->dmb_cnt));
>   }
>   
>   static void smc_lo_dev_release(struct device *dev)
> diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
> index 24ab9d747613..9156a6c37e65 100644
> --- a/net/smc/smc_loopback.h
> +++ b/net/smc/smc_loopback.h
> @@ -30,6 +30,7 @@ struct smc_lo_dmb_node {
>   	u32 sba_idx;
>   	void *cpu_addr;
>   	dma_addr_t dma_addr;
> +	refcount_t refcnt;
>   };
>   
>   struct smc_lo_dev {
> @@ -37,9 +38,11 @@ struct smc_lo_dev {
>   	struct device dev;
>   	u16 chid;
>   	struct smcd_gid local_gid;
> +	atomic_t dmb_cnt;
>   	rwlock_t dmb_ht_lock;
>   	DECLARE_BITMAP(sba_idx_mask, SMC_LO_MAX_DMBS);
>   	DECLARE_HASHTABLE(dmb_ht, SMC_LO_DMBS_HASH_BITS);
> +	wait_queue_head_t ldev_release;
>   };
>   #endif
>   

Re: [PATCH net-next v2 11/11] net/smc: implement DMB-merged operations of loopback-ism

[Wen Gu]

On 2024/3/12 16:06, Jan Karcher wrote:
> 
> 
> On 07/03/2024 10:55, Wen Gu wrote:
>> This implements operations related to merging sndbuf with peer DMB in
>> loopback-ism. The DMB won't be freed until no sndbuf is attached to it.
> 
> Hi Wen Gu,
> 
> while I'm still reviewing let me drop a lockdep finding.
> 
>>
>> Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
>> ---
>>   net/smc/smc_loopback.c | 136 +++++++++++++++++++++++++++++++++++------
>>   net/smc/smc_loopback.h |   3 +
>>   2 files changed, 119 insertions(+), 20 deletions(-)
>>
>> diff --git a/net/smc/smc_loopback.c b/net/smc/smc_loopback.c
>> index 6828e0ad3e90..7e772f3772de 100644
>> --- a/net/smc/smc_loopback.c
>> +++ b/net/smc/smc_loopback.c
> 
> [...]
> 
>> @@ -170,8 +249,22 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
>>   {
>>       struct smc_lo_dmb_node *rmb_node = NULL, *tmp_node;
>>       struct smc_lo_dev *ldev = smcd->priv;
>> -
>> -    read_lock(&ldev->dmb_ht_lock);
>> +    struct smc_connection *conn;
>> +
>> +    if (!sf)
>> +        /* since sndbuf is merged with peer DMB, there is
>> +         * no need to copy data from sndbuf to peer DMB.
>> +         */
>> +        return 0;
>> +
>> +    /* read_lock_bh() is used here just to make lockdep
>> +     * happy, because spin_(un)lock_bh(&conn->send_lock) wraps
>> +     * smc_lo_move_data() and if we use read_lock() here, lockdep
>> +     * will complain about SOFTIRQ-safe -> SOFTIRQ-unsafe lock
>> +     * order detected, but in fact ldev->dmb_ht_lock will never
>> +     * be held in bh context.
>> +     */
>> +    read_lock_bh(&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;
>> @@ -182,19 +275,14 @@ static int smc_lo_move_data(struct smcd_dev *smcd, u64 dmb_tok,
>>           read_unlock(&ldev->dmb_ht_lock);
>>           return -EINVAL;
>>       }
>> -    read_unlock(&ldev->dmb_ht_lock);
>> +    read_unlock_bh(&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);
>> -        else
>> -            return -EPIPE;
>> -    }
>> +    conn = smcd->conn[rmb_node->sba_idx];
>> +    if (!conn || conn->killed)
>> +        return -EPIPE;
>> +    smcd_cdc_rx_handler(conn);
> 
> [ 2385.528515] ============================================
> [ 2385.528517] WARNING: possible recursive locking detected
> [ 2385.528519] 6.8.0-loopback_ism-g30af186e8a18-dirty #12 Not tainted
> [ 2385.528521] --------------------------------------------
> [ 2385.528522] smcapp/51326 is trying to acquire lock:
> [ 2385.528524] 000000018707a128 (&smc->conn.send_lock){+...}-{2:2}, at: smc_tx_sndbuf_nonempty+0xba/0x1c0 [smc]
> [ 2385.528552]
>                 but task is already holding lock:
> [ 2385.528554] 0000000187078728 (&smc->conn.send_lock){+...}-{2:2}, at: smc_cdc_get_slot_and_msg_send+0x66/0xa0 [smc]
> [ 2385.528568]
>                 other info that might help us debug this:
> [ 2385.528570]  Possible unsafe locking scenario:
> 
> [ 2385.528572]        CPU0
> [ 2385.528573]        ----
> [ 2385.528574]   lock(&smc->conn.send_lock);
> [ 2385.528576]   lock(&smc->conn.send_lock);
> [ 2385.528579]
>                  *** DEADLOCK ***
> 
> [ 2385.528580]  May be due to missing lock nesting notation
> 
> [ 2385.528582] 3 locks held by smcapp/51326:
> [ 2385.528584]  #0: 0000000187078378 (sk_lock-AF_SMC){+.+.}-{0:0}, at: smc_recvmsg+0x3c/0x2b0 [smc]
> [ 2385.528598]  #1: 0000000187078728 (&smc->conn.send_lock){+...}-{2:2}, at: smc_cdc_get_slot_and_msg_send+0x66/0xa0 [smc]
> [ 2385.528613]  #2: 0000000187079ce8 (slock-AF_SMC){+...}-{2:2}, at: smc_cdc_msg_recv+0x56/0xe0 [smc]
> [ 2385.528627]
>                 stack backtrace:
> [ 2385.528660] CPU: 3 PID: 51326 Comm: smcapp Not tainted 6.8.0-loopback_ism-g30af186e8a18-dirty #12
> [ 2385.528663] Hardware name: IBM 3906 M04 704 (LPAR)
> [ 2385.528664] Call Trace:
> [ 2385.528666]  [<000000012db60788>] dump_stack_lvl+0x90/0x120
> [ 2385.528671]  [<000000012cc6d088>] validate_chain+0x560/0x960
> [ 2385.528677]  [<000000012cc6f644>] __lock_acquire+0x654/0xd58
> [ 2385.528680]  [<000000012cc70a04>] lock_acquire.part.0+0xec/0x260
> [ 2385.528683]  [<000000012cc70c24>] lock_acquire+0xac/0x170
> [ 2385.528687]  [<000000012dba4ccc>] _raw_spin_lock_bh+0x5c/0xb0
> [ 2385.528690]  [<000003ff80453b32>] smc_tx_sndbuf_nonempty+0xba/0x1c0 [smc]
> [ 2385.528702]  [<000003ff8045428a>] smc_tx_pending+0x32/0x60 [smc]
> [ 2385.528712]  [<000003ff80451f02>] smc_cdc_msg_recv_action+0x3c2/0x528 [smc]
> [ 2385.528723]  [<000003ff804520cc>] smc_cdc_msg_recv+0x64/0xe0 [smc]
> [ 2385.528734]  [<000003ff80452a4c>] smcd_cdc_rx_handler+0x64/0x70 [smc]
> [ 2385.528745]  [<000003ff80459f7e>] smc_lo_move_data+0xde/0x100 [smc]
> [ 2385.528755]  [<000003ff804533e0>] smcd_tx_ism_write+0x68/0x90 [smc]
> [ 2385.528766]  [<000003ff804528a4>] smcd_cdc_msg_send+0x74/0x118 [smc]
> [ 2385.528776]  [<000003ff804529b8>] smc_cdc_get_slot_and_msg_send+0x70/0xa0 [smc]
> [ 2385.528788]  [<000003ff804543ec>] smc_tx_consumer_update+0xe4/0x1b0 [smc]
> [ 2385.528798]  [<000003ff8045458e>] smc_rx_update_consumer+0x86/0x170 [smc]
> [ 2385.528809]  [<000003ff80455ba8>] smc_rx_recvmsg+0x3b8/0x6e8 [smc]
> [ 2385.528820]  [<000003ff804388a4>] smc_recvmsg+0xdc/0x2b0 [smc]
> [ 2385.528831]  [<000000012d8a6d58>] sock_recvmsg+0x70/0xb0
> [ 2385.528837]  [<000000012d8aa0c8>] __sys_recvfrom+0xa8/0x128
> [ 2385.528840]  [<000000012d8ab3ca>] __do_sys_socketcall+0x1ca/0x398
> [ 2385.528844]  [<000000012db8d4c4>] __do_syscall+0x244/0x308
> [ 2385.528847]  [<000000012dba6140>] system_call+0x70/0x98
> [ 2385.528850] INFO: lockdep is turned off.
> 
> 
> I did not investigate deeper, yet. Just an early heads up that there might be something broken.
> 

Thank you for reminding, Jan. I think it is because that I used smcd_cdc_rx_handler(),
which may acquire conn->send_lock, in smc_lo_move_data() where the send_lock has been
held. I reproduced this issue and will fix it in v3.

Thanks!

> Thank you
> - Jan
> 
> 
>>       return 0;
>>   }
>> @@ -226,6 +314,9 @@ 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,
>> +    .support_dmb_nocopy = smc_lo_support_dmb_nocopy,
>> +    .attach_dmb = smc_lo_attach_dmb,
>> +    .detach_dmb = smc_lo_detach_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,
>> @@ -304,12 +395,17 @@ 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);
>> +    atomic_set(&ldev->dmb_cnt, 0);
>> +    init_waitqueue_head(&ldev->ldev_release);
>> +
>>       return smcd_lo_register_dev(ldev);
>>   }
>>   static void smc_lo_dev_exit(struct smc_lo_dev *ldev)
>>   {
>>       smcd_lo_unregister_dev(ldev);
>> +    if (atomic_read(&ldev->dmb_cnt))
>> +        wait_event(ldev->ldev_release, !atomic_read(&ldev->dmb_cnt));
>>   }
>>   static void smc_lo_dev_release(struct device *dev)
>> diff --git a/net/smc/smc_loopback.h b/net/smc/smc_loopback.h
>> index 24ab9d747613..9156a6c37e65 100644
>> --- a/net/smc/smc_loopback.h
>> +++ b/net/smc/smc_loopback.h
>> @@ -30,6 +30,7 @@ struct smc_lo_dmb_node {
>>       u32 sba_idx;
>>       void *cpu_addr;
>>       dma_addr_t dma_addr;
>> +    refcount_t refcnt;
>>   };
>>   struct smc_lo_dev {
>> @@ -37,9 +38,11 @@ struct smc_lo_dev {
>>       struct device dev;
>>       u16 chid;
>>       struct smcd_gid local_gid;
>> +    atomic_t dmb_cnt;
>>       rwlock_t dmb_ht_lock;
>>       DECLARE_BITMAP(sba_idx_mask, SMC_LO_MAX_DMBS);
>>       DECLARE_HASHTABLE(dmb_ht, SMC_LO_DMBS_HASH_BITS);
>> +    wait_queue_head_t ldev_release;
>>   };
>>   #endif