[PATCH 17/23] cxl/mbox: Add exclusive kernel command support

[Dan Williams <dan.j.williams@intel.com>]

The CXL_PMEM driver expects exclusive control of the label storage area
space. Similar to the LIBNVDIMM expectation that the label storage area
is only writable from userspace when the corresponding memory device is
not active in any region, the expectation is the native CXL_PCI UAPI
path is disabled while the cxl_nvdimm for a given cxl_memdev device is
active in LIBNVDIMM.

Add the ability to toggle the availability of a given command for the
UAPI path. Use that new capability to shutdown changes to partitions and
the label storage area while the cxl_nvdimm device is actively proxying
commands for LIBNVDIMM.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/core/mbox.c |    5 +++++
 drivers/cxl/cxlmem.h    |    2 ++
 drivers/cxl/pmem.c      |   35 +++++++++++++++++++++++++++++------
 3 files changed, 36 insertions(+), 6 deletions(-)

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 23100231e246..f26962d7cb65 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -409,6 +409,11 @@ static int handle_mailbox_cmd_from_user(struct cxl_mem *cxlm,
 		}
 	}
 
+	if (test_bit(cmd->info.id, cxlm->exclusive_cmds)) {
+		rc = -EBUSY;
+		goto out;
+	}
+
 	dev_dbg(dev,
 		"Submitting %s command for user\n"
 		"\topcode: %x\n"
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index df4f3636a999..f6cfe84a064c 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -102,6 +102,7 @@ struct cxl_mbox_cmd {
  * @mbox_mutex: Mutex to synchronize mailbox access.
  * @firmware_version: Firmware version for the memory device.
  * @enabled_cmds: Hardware commands found enabled in CEL.
+ * @exclusive_cmds: Commands that are kernel-internal only
  * @pmem_range: Persistent memory capacity information.
  * @ram_range: Volatile memory capacity information.
  * @mbox_send: @dev specific transport for transmitting mailbox commands
@@ -117,6 +118,7 @@ struct cxl_mem {
 	struct mutex mbox_mutex; /* Protects device mailbox and firmware */
 	char firmware_version[0x10];
 	DECLARE_BITMAP(enabled_cmds, CXL_MEM_COMMAND_ID_MAX);
+	DECLARE_BITMAP(exclusive_cmds, CXL_MEM_COMMAND_ID_MAX);
 
 	struct range pmem_range;
 	struct range ram_range;
diff --git a/drivers/cxl/pmem.c b/drivers/cxl/pmem.c
index 9652c3ee41e7..11410df77444 100644
--- a/drivers/cxl/pmem.c
+++ b/drivers/cxl/pmem.c
@@ -16,9 +16,23 @@
  */
 static struct workqueue_struct *cxl_pmem_wq;
 
-static void unregister_nvdimm(void *nvdimm)
+static void unregister_nvdimm(void *_cxl_nvd)
 {
-	nvdimm_delete(nvdimm);
+	struct cxl_nvdimm *cxl_nvd = _cxl_nvd;
+	struct cxl_memdev *cxlmd = cxl_nvd->cxlmd;
+	struct cxl_mem *cxlm = cxlmd->cxlm;
+	struct device *dev = &cxl_nvd->dev;
+	struct nvdimm *nvdimm;
+
+	nvdimm = dev_get_drvdata(dev);
+	if (nvdimm)
+		nvdimm_delete(nvdimm);
+
+	mutex_lock(&cxlm->mbox_mutex);
+	clear_bit(CXL_MEM_COMMAND_ID_SET_PARTITION_INFO, cxlm->exclusive_cmds);
+	clear_bit(CXL_MEM_COMMAND_ID_SET_SHUTDOWN_STATE, cxlm->exclusive_cmds);
+	clear_bit(CXL_MEM_COMMAND_ID_SET_LSA, cxlm->exclusive_cmds);
+	mutex_unlock(&cxlm->mbox_mutex);
 }
 
 static int match_nvdimm_bridge(struct device *dev, const void *data)
@@ -39,6 +53,8 @@ static struct cxl_nvdimm_bridge *cxl_find_nvdimm_bridge(void)
 static int cxl_nvdimm_probe(struct device *dev)
 {
 	struct cxl_nvdimm *cxl_nvd = to_cxl_nvdimm(dev);
+	struct cxl_memdev *cxlmd = cxl_nvd->cxlmd;
+	struct cxl_mem *cxlm = cxlmd->cxlm;
 	struct cxl_nvdimm_bridge *cxl_nvb;
 	unsigned long flags = 0;
 	struct nvdimm *nvdimm;
@@ -52,17 +68,24 @@ static int cxl_nvdimm_probe(struct device *dev)
 	if (!cxl_nvb->nvdimm_bus)
 		goto out;
 
+	mutex_lock(&cxlm->mbox_mutex);
+	set_bit(CXL_MEM_COMMAND_ID_SET_PARTITION_INFO, cxlm->exclusive_cmds);
+	set_bit(CXL_MEM_COMMAND_ID_SET_SHUTDOWN_STATE, cxlm->exclusive_cmds);
+	set_bit(CXL_MEM_COMMAND_ID_SET_LSA, cxlm->exclusive_cmds);
+	mutex_unlock(&cxlm->mbox_mutex);
+
 	set_bit(NDD_LABELING, &flags);
 	nvdimm = nvdimm_create(cxl_nvb->nvdimm_bus, cxl_nvd, NULL, flags, 0, 0,
 			       NULL);
-	if (!nvdimm)
-		goto out;
-
-	rc = devm_add_action_or_reset(dev, unregister_nvdimm, nvdimm);
+	dev_set_drvdata(dev, nvdimm);
+	rc = devm_add_action_or_reset(dev, unregister_nvdimm, cxl_nvd);
 out:
 	device_unlock(&cxl_nvb->dev);
 	put_device(&cxl_nvb->dev);
 
+	if (!nvdimm && rc == 0)
+		rc = -ENOMEM;
+
 	return rc;
 }