net/smc: disable SEID on non-s390 archs where virtual ISM may be used

The system EID (SEID) is an internal EID used by SMC-D to represent the
s390 physical machine that OS is executing on. On s390 architecture, it
predefined by fixed string and part of cpuid and is enabled regardless
of whether underlay device is virtual ISM or platform firmware ISM.

However on non-s390 architectures where SMC-D can be used with virtual
ISM devices, there is no similar information to identify physical
machines, especially in virtualization scenarios. So in such cases, SEID
is forcibly disabled and the user-defined UEID will be used to represent
the communicable space.

Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Reviewed-and-tested-by: Wenjia Zhang <wenjia@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_clc.c

@@ -155,10 +155,12 @@ static int smc_clc_ueid_remove(char *ueid)
  rc = 0;
  }
  }
+#if IS_ENABLED(CONFIG_S390)
  if (!rc && !smc_clc_eid_table.ueid_cnt) {
  smc_clc_eid_table.seid_enabled = 1;
  rc = -EAGAIN; /* indicate success and enabling of seid */
  }
+#endif
  write_unlock(&smc_clc_eid_table.lock);
  return rc;
 }
@@ -273,22 +275,30 @@ int smc_nl_dump_seid(struct sk_buff *skb, struct netlink_callback *cb)
 
 int smc_nl_enable_seid(struct sk_buff *skb, struct genl_info *info)
 {
+#if IS_ENABLED(CONFIG_S390)
  write_lock(&smc_clc_eid_table.lock);
  smc_clc_eid_table.seid_enabled = 1;
  write_unlock(&smc_clc_eid_table.lock);
  return 0;
+#else
+ return -EOPNOTSUPP;
+#endif
 }
 
 int smc_nl_disable_seid(struct sk_buff *skb, struct genl_info *info)
 {
  int rc = 0;
 
+#if IS_ENABLED(CONFIG_S390)
  write_lock(&smc_clc_eid_table.lock);
  if (!smc_clc_eid_table.ueid_cnt)
  rc = -ENOENT;
  else
  smc_clc_eid_table.seid_enabled = 0;
  write_unlock(&smc_clc_eid_table.lock);
+#else
+ rc = -EOPNOTSUPP;
+#endif
  return rc;
 }
 
@@ -1328,7 +1338,11 @@ void __init smc_clc_init(void)
  INIT_LIST_HEAD(&smc_clc_eid_table.list);
  rwlock_init(&smc_clc_eid_table.lock);
  smc_clc_eid_table.ueid_cnt = 0;
+#if IS_ENABLED(CONFIG_S390)
  smc_clc_eid_table.seid_enabled = 1;
+#else
+ smc_clc_eid_table.seid_enabled = 0;
+#endif
 }
 
 void smc_clc_exit(void)