cxl/mem: Introduce security state sysfs file

Add a read-only sysfs file to display the security state
of a device (currently only pmem):

    /sys/bus/cxl/devices/memX/security/state

This introduces a cxl_security_state structure that is
to be the placeholder for common CXL security features.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20230612181038.14421-3-dave@stgolabs.net
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Documentation/ABI/testing/sysfs-bus-cxl

@@ -58,6 +58,16 @@ Description:
 		affinity for this device.
 
 
+What:		/sys/bus/cxl/devices/memX/security/state
+Date:		June, 2023
+KernelVersion:	v6.5
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) Reading this file will display the CXL security state for
+		that device. Such states can be: 'disabled', or those available
+		only for persistent memory: 'locked', 'unlocked' or 'frozen'.
+
+
 What:		/sys/bus/cxl/devices/*/devtype
 Date:		June, 2021
 KernelVersion:	v5.14

drivers/cxl/core/memdev.c

@@ -107,6 +107,28 @@ static ssize_t numa_node_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(numa_node);
 
+static ssize_t security_state_show(struct device *dev,
+				   struct device_attribute *attr,
+				   char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	unsigned long state = cxlds->security.state;
+
+	if (!(state & CXL_PMEM_SEC_STATE_USER_PASS_SET))
+		return sysfs_emit(buf, "disabled\n");
+	if (state & CXL_PMEM_SEC_STATE_FROZEN ||
+	    state & CXL_PMEM_SEC_STATE_MASTER_PLIMIT ||
+	    state & CXL_PMEM_SEC_STATE_USER_PLIMIT)
+		return sysfs_emit(buf, "frozen\n");
+	if (state & CXL_PMEM_SEC_STATE_LOCKED)
+		return sysfs_emit(buf, "locked\n");
+	else
+		return sysfs_emit(buf, "unlocked\n");
+}
+static struct device_attribute dev_attr_security_state =
+	__ATTR(state, 0444, security_state_show, NULL);
+
 static int cxl_get_poison_by_memdev(struct cxl_memdev *cxlmd)
 {
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
@@ -352,6 +374,11 @@ static struct attribute *cxl_memdev_ram_attributes[] = {
 	NULL,
 };
 
+static struct attribute *cxl_memdev_security_attributes[] = {
+	&dev_attr_security_state.attr,
+	NULL,
+};
+
 static umode_t cxl_memdev_visible(struct kobject *kobj, struct attribute *a,
 				  int n)
 {
@@ -375,10 +402,16 @@ static struct attribute_group cxl_memdev_pmem_attribute_group = {
 	.attrs = cxl_memdev_pmem_attributes,
 };
 
+static struct attribute_group cxl_memdev_security_attribute_group = {
+	.name = "security",
+	.attrs = cxl_memdev_security_attributes,
+};
+
 static const struct attribute_group *cxl_memdev_attribute_groups[] = {
 	&cxl_memdev_attribute_group,
 	&cxl_memdev_ram_attribute_group,
 	&cxl_memdev_pmem_attribute_group,
+	&cxl_memdev_security_attribute_group,
 	NULL,
 };
 

drivers/cxl/cxlmem.h

@@ -260,6 +260,15 @@ struct cxl_poison_state {
 	struct mutex lock;  /* Protect reads of poison list */
 };
 
+/**
+ * struct cxl_security_state - Device security state
+ *
+ * @state: state of last security operation
+ */
+struct cxl_security_state {
+	unsigned long state;
+};
+
 /**
  * struct cxl_dev_state - The driver device state
  *
@@ -336,6 +345,7 @@ struct cxl_dev_state {
 
 	struct cxl_event_state event;
 	struct cxl_poison_state poison;
+	struct cxl_security_state security;
 
 	struct rcuwait mbox_wait;
 	int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);

drivers/cxl/security.c

@@ -34,6 +34,9 @@ static unsigned long cxl_pmem_get_security_flags(struct nvdimm *nvdimm,
 		return 0;
 
 	sec_out = le32_to_cpu(out.flags);
+	/* cache security state */
+	cxlds->security.state = sec_out;
+
 	if (ptype == NVDIMM_MASTER) {
 		if (sec_out & CXL_PMEM_SEC_STATE_MASTER_PASS_SET)
 			set_bit(NVDIMM_SECURITY_UNLOCKED, &security_flags);