net/smc: define a reserved CHID range for virtual ISM devices

JIRA: https://issues.redhat.com/browse/RHEL-73484

commit 8dd512d
Author: Wen Gu <guwen@linux.alibaba.com>
Date:   Tue Dec 19 22:26:12 2023 +0800

    net/smc: define a reserved CHID range for virtual ISM devices

    According to virtual ISM support feature defined by SMCv2.1, CHIDs in
    the range 0xFF00 to 0xFFFF are reserved for use by virtual ISM devices.

    And two helpers are introduced to distinguish virtual ISM devices from
    the existing platform firmware ISM devices.

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

Signed-off-by: Mete Durlu <mdurlu@redhat.com>

Author: Mete Durlu

net/smc/smc_ism.h

@@ -15,6 +15,8 @@
 
 #include "smc.h"
 
+#define SMC_VIRTUAL_ISM_CHID_MASK	0xFF00
+
 struct smcd_dev_list {	/* List of SMCD devices */
 	struct list_head list;
 	struct mutex mutex;	/* Protects list of devices */
@@ -56,4 +58,22 @@ static inline int smc_ism_write(struct smcd_dev *smcd, u64 dmb_tok,
 	return rc < 0 ? rc : 0;
 }
 
+static inline bool __smc_ism_is_virtual(u16 chid)
+{
+	/* CHIDs in range of 0xFF00 to 0xFFFF are reserved
+	 * for virtual ISM device.
+	 *
+	 * loopback-ism:	0xFFFF
+	 * virtio-ism:		0xFF00 ~ 0xFFFE
+	 */
+	return ((chid & 0xFF00) == 0xFF00);
+}
+
+static inline bool smc_ism_is_virtual(struct smcd_dev *smcd)
+{
+	u16 chid = smcd->ops->get_chid(smcd);
+
+	return __smc_ism_is_virtual(chid);
+}
+
 #endif