cxl/mem: Support Secure Erase

Implement support for the non-pmem exclusive secure erase, per
CXL specs. Create a write-only 'security/erase' sysfs file to
perform the requested operation.

As with the sanitation this requires the device being offline
and thus no active HPA-DPA decoding.

The expectation is that userspace can use it such as:

	cxl disable-memdev memX
	echo 1 > /sys/bus/cxl/devices/memX/security/erase
	cxl enable-memdev memX

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Link: https://lore.kernel.org/r/20230612181038.14421-7-dave@stgolabs.net
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Author: Davidlohr Bueso

Documentation/ABI/testing/sysfs-bus-cxl

@@ -85,6 +85,16 @@ Description:
 		the device to be not be actively decoding any HPA ranges.
 
 
+What            /sys/bus/cxl/devices/memX/security/erase
+Date:           June, 2023
+KernelVersion:  v6.5
+Contact:        linux-cxl@vger.kernel.org
+Description:
+		(WO) Write a boolean 'true' string value to this attribute to
+		secure erase user data by changing the media encryption keys for
+		all user data areas of the device.
+
+
 What:		/sys/bus/cxl/devices/*/devtype
 Date:		June, 2021
 KernelVersion:	v5.14

drivers/cxl/core/mbox.c

@@ -1102,7 +1102,7 @@ int cxl_mem_sanitize(struct cxl_dev_state *cxlds, u16 cmd)
 	};
 	struct cxl_mbox_cmd mbox_cmd = { .opcode = cmd };
 
-	if (cmd != CXL_MBOX_OP_SANITIZE)
+	if (cmd != CXL_MBOX_OP_SANITIZE && cmd != CXL_MBOX_OP_SECURE_ERASE)
 		return -EINVAL;
 
 	rc = cxl_internal_send_cmd(cxlds, &sec_cmd);
@@ -1120,6 +1120,10 @@ int cxl_mem_sanitize(struct cxl_dev_state *cxlds, u16 cmd)
 	if (sec_out & CXL_PMEM_SEC_STATE_USER_PASS_SET)
 		return -EINVAL;
 
+	if (cmd == CXL_MBOX_OP_SECURE_ERASE &&
+	    sec_out & CXL_PMEM_SEC_STATE_LOCKED)
+		return -EINVAL;
+
 	rc = cxl_internal_send_cmd(cxlds, &mbox_cmd);
 	if (rc < 0) {
 		dev_err(cxlds->dev, "Failed to sanitize device : %d", rc);

drivers/cxl/core/memdev.c

@@ -163,6 +163,33 @@ static ssize_t security_sanitize_store(struct device *dev,
 static struct device_attribute dev_attr_security_sanitize =
 	__ATTR(sanitize, 0200, NULL, security_sanitize_store);
 
+static ssize_t security_erase_store(struct device *dev,
+				    struct device_attribute *attr,
+				    const char *buf, size_t len)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	struct cxl_port *port = dev_get_drvdata(&cxlmd->dev);
+	ssize_t rc;
+	bool erase;
+
+	if (kstrtobool(buf, &erase) || !erase)
+		return -EINVAL;
+
+	if (!port || !is_cxl_endpoint(port))
+		return -EINVAL;
+
+	/* ensure no regions are mapped to this memdev */
+	if (port->commit_end != -1)
+		return -EBUSY;
+
+	rc = cxl_mem_sanitize(cxlds, CXL_MBOX_OP_SECURE_ERASE);
+
+	return rc ? rc : len;
+}
+static struct device_attribute dev_attr_security_erase =
+	__ATTR(erase, 0200, NULL, security_erase_store);
+
 static int cxl_get_poison_by_memdev(struct cxl_memdev *cxlmd)
 {
 	struct cxl_dev_state *cxlds = cxlmd->cxlds;
@@ -411,6 +438,7 @@ static struct attribute *cxl_memdev_ram_attributes[] = {
 static struct attribute *cxl_memdev_security_attributes[] = {
 	&dev_attr_security_state.attr,
 	&dev_attr_security_sanitize.attr,
+	&dev_attr_security_erase.attr,
 	NULL,
 };
 

drivers/cxl/cxlmem.h

@@ -388,6 +388,7 @@ enum cxl_opcode {
 	CXL_MBOX_OP_SCAN_MEDIA		= 0x4304,
 	CXL_MBOX_OP_GET_SCAN_MEDIA	= 0x4305,
 	CXL_MBOX_OP_SANITIZE		= 0x4400,
+	CXL_MBOX_OP_SECURE_ERASE	= 0x4401,
 	CXL_MBOX_OP_GET_SECURITY_STATE	= 0x4500,
 	CXL_MBOX_OP_SET_PASSPHRASE	= 0x4501,
 	CXL_MBOX_OP_DISABLE_PASSPHRASE	= 0x4502,