[PATCH net-next v3 08/11] net/smc: add operations to merge sndbuf with peer DMB

Wen Gu
2024-03-12T14:28:18Z

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