cxl/pmem: Add "Unlock" security command support

Create callback function to support the nvdimm_security_ops() ->unlock()
callback. Translate the operation to send "Unlock" security command for CXL
mem device.

When the mem device is unlocked, cpu_cache_invalidate_memregion() is called
in order to invalidate all CPU caches before attempting to access the mem
device.

See CXL rev3.0 spec section 8.2.9.8.6.4 for reference.

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/166983614167.2734609.15124543712487741176.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -69,6 +69,7 @@ static struct cxl_mem_command cxl_mem_commands[CXL_MEM_COMMAND_ID_MAX] = {
 	CXL_CMD(SET_PASSPHRASE, 0x60, 0, 0),
 	CXL_CMD(DISABLE_PASSPHRASE, 0x40, 0, 0),
 	CXL_CMD(FREEZE_SECURITY, 0, 0, 0),
+	CXL_CMD(UNLOCK, 0x20, 0, 0),
 };
 
 /*

drivers/cxl/cxlmem.h

@@ -276,6 +276,7 @@ enum cxl_opcode {
 	CXL_MBOX_OP_GET_SECURITY_STATE	= 0x4500,
 	CXL_MBOX_OP_SET_PASSPHRASE	= 0x4501,
 	CXL_MBOX_OP_DISABLE_PASSPHRASE	= 0x4502,
+	CXL_MBOX_OP_UNLOCK		= 0x4503,
 	CXL_MBOX_OP_FREEZE_SECURITY	= 0x4504,
 	CXL_MBOX_OP_MAX			= 0x10000
 };

drivers/cxl/security.c

@@ -5,6 +5,7 @@
 #include <linux/module.h>
 #include <linux/async.h>
 #include <linux/slab.h>
+#include <linux/memregion.h>
 #include "cxlmem.h"
 #include "cxl.h"
 
@@ -96,11 +97,37 @@ static int cxl_pmem_security_freeze(struct nvdimm *nvdimm)
 	return cxl_mbox_send_cmd(cxlds, CXL_MBOX_OP_FREEZE_SECURITY, NULL, 0, NULL, 0);
 }
 
+static int cxl_pmem_security_unlock(struct nvdimm *nvdimm,
+				    const struct nvdimm_key_data *key_data)
+{
+	struct cxl_nvdimm *cxl_nvd = nvdimm_provider_data(nvdimm);
+	struct cxl_memdev *cxlmd = cxl_nvd->cxlmd;
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	u8 pass[NVDIMM_PASSPHRASE_LEN];
+	int rc;
+
+	if (!cpu_cache_has_invalidate_memregion())
+		return -EINVAL;
+
+	memcpy(pass, key_data->data, NVDIMM_PASSPHRASE_LEN);
+	rc = cxl_mbox_send_cmd(cxlds, CXL_MBOX_OP_UNLOCK,
+			       pass, NVDIMM_PASSPHRASE_LEN, NULL, 0);
+	if (rc < 0)
+		return rc;
+
+	/* DIMM unlocked, invalidate all CPU caches before we read it */
+	cpu_cache_invalidate_memregion(IORES_DESC_PERSISTENT_MEMORY);
+	return 0;
+}
+
 static const struct nvdimm_security_ops __cxl_security_ops = {
 	.get_flags = cxl_pmem_get_security_flags,
 	.change_key = cxl_pmem_security_change_key,
 	.disable = cxl_pmem_security_disable,
 	.freeze = cxl_pmem_security_freeze,
+	.unlock = cxl_pmem_security_unlock,
 };
 
 const struct nvdimm_security_ops *cxl_security_ops = &__cxl_security_ops;
+
+MODULE_IMPORT_NS(DEVMEM);

include/uapi/linux/cxl_mem.h

@@ -45,6 +45,7 @@
 	___C(SET_PASSPHRASE, "Set Passphrase"),				  \
 	___C(DISABLE_PASSPHRASE, "Disable Passphrase"),			  \
 	___C(FREEZE_SECURITY, "Freeze Security"),			  \
+	___C(UNLOCK, "Unlock"),						  \
 	___C(MAX, "invalid / last command")
 
 #define ___C(a, b) CXL_MEM_COMMAND_ID_##a