cxl/mem: Enable commands via CEL

CXL devices identified by the memory-device class code must implement
the Device Command Interface (described in 8.2.9 of the CXL 2.0 spec).
While the driver already maintains a list of commands it supports, there
is still a need to be able to distinguish between commands that the
driver knows about from commands that are optionally supported by the
hardware.

The Command Effects Log (CEL) is specified in the CXL 2.0 specification.
The CEL is one of two types of logs, the other being vendor specific.
They are distinguished in hardware/spec via UUID. The CEL is useful for
2 things:
1. Determine which optional commands are supported by the CXL device.
2. Enumerate any vendor specific commands

The CEL is used by the driver to determine which commands are available
in the hardware and therefore which commands userspace is allowed to
execute. The set of enabled commands might be a subset of commands which
are advertised in UAPI via CXL_MEM_SEND_COMMAND IOCTL.

With the CEL enabling comes a internal flag to indicate a base set of
commands that are enabled regardless of CEL. Such commands are required
for basic interaction with the hardware and thus can be useful in debug
cases, for example if the CEL is corrupted.

The implementation leaves the statically defined table of commands and
supplements it with a bitmap to determine commands that are enabled.
This organization was chosen for the following reasons:
- Smaller memory footprint. Doesn't need a table per device.
- Reduce memory allocation complexity.
- Fixed command IDs to opcode mapping for all devices makes development
  and debugging easier.
- Certain helpers are easily achievable, like cxl_for_each_cmd().
Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com> (v2)
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> (v3)
Link: https://lore.kernel.org/r/20210217040958.1354670-7-ben.widawsky@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/cxl.h

@@ -69,6 +69,7 @@ struct cxl_memdev;
  *                (CXL 2.0 8.2.8.4.3 Mailbox Capabilities Register)
  * @mbox_mutex: Mutex to synchronize mailbox access.
  * @firmware_version: Firmware version for the memory device.
+ * @enabled_commands: Hardware commands found enabled in CEL.
  * @pmem_range: Persistent memory capacity information.
  * @ram_range: Volatile memory capacity information.
  */
@@ -84,6 +85,7 @@ struct cxl_mem {
 	size_t payload_size;
 	struct mutex mbox_mutex; /* Protects device mailbox and firmware */
 	char firmware_version[0x10];
+	unsigned long *enabled_cmds;
 
 	struct range pmem_range;
 	struct range ram_range;

drivers/cxl/mem.c

@@ -46,6 +46,8 @@ enum opcode {
 	CXL_MBOX_OP_INVALID		= 0x0000,
 	CXL_MBOX_OP_RAW			= CXL_MBOX_OP_INVALID,
 	CXL_MBOX_OP_ACTIVATE_FW		= 0x0202,
+	CXL_MBOX_OP_GET_SUPPORTED_LOGS	= 0x0400,
+	CXL_MBOX_OP_GET_LOG		= 0x0401,
 	CXL_MBOX_OP_IDENTIFY		= 0x4000,
 	CXL_MBOX_OP_SET_PARTITION_INFO	= 0x4101,
 	CXL_MBOX_OP_SET_LSA		= 0x4103,
@@ -108,10 +110,28 @@ static DEFINE_IDA(cxl_memdev_ida);
 static struct dentry *cxl_debugfs;
 static bool cxl_raw_allow_all;
 
+enum {
+	CEL_UUID,
+	VENDOR_DEBUG_UUID,
+};
+
+/* See CXL 2.0 Table 170. Get Log Input Payload */
+static const uuid_t log_uuid[] = {
+	[CEL_UUID] = UUID_INIT(0xda9c0b5, 0xbf41, 0x4b78, 0x8f, 0x79, 0x96,
+			       0xb1, 0x62, 0x3b, 0x3f, 0x17),
+	[VENDOR_DEBUG_UUID] = UUID_INIT(0xe1819d9, 0x11a9, 0x400c, 0x81, 0x1f,
+					0xd6, 0x07, 0x19, 0x40, 0x3d, 0x86),
+};
+
 /**
  * struct cxl_mem_command - Driver representation of a memory device command
  * @info: Command information as it exists for the UAPI
  * @opcode: The actual bits used for the mailbox protocol
+ * @flags: Set of flags effecting driver behavior.
+ *
+ *  * %CXL_CMD_FLAG_FORCE_ENABLE: In cases of error, commands with this flag
+ *    will be enabled by the driver regardless of what hardware may have
+ *    advertised.
  *
  * The cxl_mem_command is the driver's internal representation of commands that
  * are supported by the driver. Some of these commands may not be supported by
@@ -123,9 +143,12 @@ static bool cxl_raw_allow_all;
 struct cxl_mem_command {
 	struct cxl_command_info info;
 	enum opcode opcode;
+	u32 flags;
+#define CXL_CMD_FLAG_NONE 0
+#define CXL_CMD_FLAG_FORCE_ENABLE BIT(0)
 };
 
-#define CXL_CMD(_id, sin, sout)                                                \
+#define CXL_CMD(_id, sin, sout, _flags)                                        \
 	[CXL_MEM_COMMAND_ID_##_id] = {                                         \
 	.info =	{                                                              \
 			.id = CXL_MEM_COMMAND_ID_##_id,                        \
@@ -133,6 +156,7 @@ struct cxl_mem_command {
 			.size_out = sout,                                      \
 		},                                                             \
 	.opcode = CXL_MBOX_OP_##_id,                                           \
+	.flags = _flags,                                                       \
 	}
 
 /*
@@ -142,10 +166,11 @@ struct cxl_mem_command {
  * 0, and the user passed in 1, it is an error.
  */
 static struct cxl_mem_command mem_commands[] = {
-	CXL_CMD(IDENTIFY, 0, 0x43),
+	CXL_CMD(IDENTIFY, 0, 0x43, CXL_CMD_FLAG_FORCE_ENABLE),
 #ifdef CONFIG_CXL_MEM_RAW_COMMANDS
-	CXL_CMD(RAW, ~0, ~0),
+	CXL_CMD(RAW, ~0, ~0, 0),
 #endif
+	CXL_CMD(GET_SUPPORTED_LOGS, 0, ~0, CXL_CMD_FLAG_FORCE_ENABLE),
 };
 
 /*
@@ -633,6 +658,10 @@ static int cxl_validate_cmd_from_user(struct cxl_mem *cxlm,
 	c = &mem_commands[send_cmd->id];
 	info = &c->info;
 
+	/* Check that the command is enabled for hardware */
+	if (!test_bit(info->id, cxlm->enabled_cmds))
+		return -ENOTTY;
+
 	/* Check the input buffer is the expected size */
 	if (info->size_in >= 0 && info->size_in != send_cmd->in.size)
 		return -ENOMEM;
@@ -757,6 +786,17 @@ static const struct file_operations cxl_memdev_fops = {
 	.llseek = noop_llseek,
 };
 
+static inline struct cxl_mem_command *cxl_mem_find_command(u16 opcode)
+{
+	struct cxl_mem_command *c;
+
+	cxl_for_each_cmd(c)
+		if (c->opcode == opcode)
+			return c;
+
+	return NULL;
+}
+
 /**
  * cxl_mem_mbox_send_cmd() - Send a mailbox command to a memory device.
  * @cxlm: The CXL memory device to communicate with.
@@ -777,9 +817,7 @@ static const struct file_operations cxl_memdev_fops = {
  *
  * Mailbox commands may execute successfully yet the device itself reported an
  * error. While this distinction can be useful for commands from userspace, the
- * kernel will only be able to use results when both are successful. It's
- * expected that all callers of this function know exactly the size of the data
- * they will consume from the hardware.
+ * kernel will only be able to use results when both are successful.
  *
  * See __cxl_mem_mbox_send_cmd()
  */
@@ -787,6 +825,7 @@ static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode,
 				 void *in, size_t in_size,
 				 void *out, size_t out_size)
 {
+	const struct cxl_mem_command *cmd = cxl_mem_find_command(opcode);
 	struct mbox_cmd mbox_cmd = {
 		.opcode = opcode,
 		.payload_in = in,
@@ -812,7 +851,11 @@ static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm, u16 opcode,
 	if (mbox_cmd.return_code != CXL_MBOX_SUCCESS)
 		return -ENXIO;
 
-	if (mbox_cmd.size_out != out_size)
+	/*
+	 * Variable sized commands can't be validated and so it's up to the
+	 * caller to do that if they wish.
+	 */
+	if (cmd->info.size_out >= 0 && mbox_cmd.size_out != out_size)
 		return -EIO;
 
 	return 0;
@@ -947,6 +990,14 @@ static struct cxl_mem *cxl_mem_create(struct pci_dev *pdev, u32 reg_lo,
 	mutex_init(&cxlm->mbox_mutex);
 	cxlm->pdev = pdev;
 	cxlm->regs = regs + offset;
+	cxlm->enabled_cmds =
+		devm_kmalloc_array(dev, BITS_TO_LONGS(cxl_cmd_count),
+				   sizeof(unsigned long),
+				   GFP_KERNEL | __GFP_ZERO);
+	if (!cxlm->enabled_cmds) {
+		dev_err(dev, "No memory available for bitmap\n");
+		return NULL;
+	}
 
 	dev_dbg(dev, "Mapped CXL Memory Device resource\n");
 	return cxlm;
@@ -1166,6 +1217,160 @@ static int cxl_mem_add_memdev(struct cxl_mem *cxlm)
 	return rc;
 }
 
+static int cxl_xfer_log(struct cxl_mem *cxlm, uuid_t *uuid, u32 size, u8 *out)
+{
+	u32 remaining = size;
+	u32 offset = 0;
+
+	while (remaining) {
+		u32 xfer_size = min_t(u32, remaining, cxlm->payload_size);
+		struct cxl_mbox_get_log {
+			uuid_t uuid;
+			__le32 offset;
+			__le32 length;
+		} __packed log = {
+			.uuid = *uuid,
+			.offset = cpu_to_le32(offset),
+			.length = cpu_to_le32(xfer_size)
+		};
+		int rc;
+
+		rc = cxl_mem_mbox_send_cmd(cxlm, CXL_MBOX_OP_GET_LOG, &log,
+					   sizeof(log), out, xfer_size);
+		if (rc < 0)
+			return rc;
+
+		out += xfer_size;
+		remaining -= xfer_size;
+		offset += xfer_size;
+	}
+
+	return 0;
+}
+
+/**
+ * cxl_walk_cel() - Walk through the Command Effects Log.
+ * @cxlm: Device.
+ * @size: Length of the Command Effects Log.
+ * @cel: CEL
+ *
+ * Iterate over each entry in the CEL and determine if the driver supports the
+ * command. If so, the command is enabled for the device and can be used later.
+ */
+static void cxl_walk_cel(struct cxl_mem *cxlm, size_t size, u8 *cel)
+{
+	struct cel_entry {
+		__le16 opcode;
+		__le16 effect;
+	} __packed * cel_entry;
+	const int cel_entries = size / sizeof(*cel_entry);
+	int i;
+
+	cel_entry = (struct cel_entry *)cel;
+
+	for (i = 0; i < cel_entries; i++) {
+		u16 opcode = le16_to_cpu(cel_entry[i].opcode);
+		struct cxl_mem_command *cmd = cxl_mem_find_command(opcode);
+
+		if (!cmd) {
+			dev_dbg(&cxlm->pdev->dev,
+				"Opcode 0x%04x unsupported by driver", opcode);
+			continue;
+		}
+
+		set_bit(cmd->info.id, cxlm->enabled_cmds);
+	}
+}
+
+struct cxl_mbox_get_supported_logs {
+	__le16 entries;
+	u8 rsvd[6];
+	struct gsl_entry {
+		uuid_t uuid;
+		__le32 size;
+	} __packed entry[];
+} __packed;
+
+static struct cxl_mbox_get_supported_logs *cxl_get_gsl(struct cxl_mem *cxlm)
+{
+	struct cxl_mbox_get_supported_logs *ret;
+	int rc;
+
+	ret = kvmalloc(cxlm->payload_size, GFP_KERNEL);
+	if (!ret)
+		return ERR_PTR(-ENOMEM);
+
+	rc = cxl_mem_mbox_send_cmd(cxlm, CXL_MBOX_OP_GET_SUPPORTED_LOGS, NULL,
+				   0, ret, cxlm->payload_size);
+	if (rc < 0) {
+		kvfree(ret);
+		return ERR_PTR(rc);
+	}
+
+	return ret;
+}
+
+/**
+ * cxl_mem_enumerate_cmds() - Enumerate commands for a device.
+ * @cxlm: The device.
+ *
+ * Returns 0 if enumerate completed successfully.
+ *
+ * CXL devices have optional support for certain commands. This function will
+ * determine the set of supported commands for the hardware and update the
+ * enabled_cmds bitmap in the @cxlm.
+ */
+static int cxl_mem_enumerate_cmds(struct cxl_mem *cxlm)
+{
+	struct cxl_mbox_get_supported_logs *gsl;
+	struct device *dev = &cxlm->pdev->dev;
+	struct cxl_mem_command *cmd;
+	int i, rc;
+
+	gsl = cxl_get_gsl(cxlm);
+	if (IS_ERR(gsl))
+		return PTR_ERR(gsl);
+
+	rc = -ENOENT;
+	for (i = 0; i < le16_to_cpu(gsl->entries); i++) {
+		u32 size = le32_to_cpu(gsl->entry[i].size);
+		uuid_t uuid = gsl->entry[i].uuid;
+		u8 *log;
+
+		dev_dbg(dev, "Found LOG type %pU of size %d", &uuid, size);
+
+		if (!uuid_equal(&uuid, &log_uuid[CEL_UUID]))
+			continue;
+
+		log = kvmalloc(size, GFP_KERNEL);
+		if (!log) {
+			rc = -ENOMEM;
+			goto out;
+		}
+
+		rc = cxl_xfer_log(cxlm, &uuid, size, log);
+		if (rc) {
+			kvfree(log);
+			goto out;
+		}
+
+		cxl_walk_cel(cxlm, size, log);
+		kvfree(log);
+
+		/* In case CEL was bogus, enable some default commands. */
+		cxl_for_each_cmd(cmd)
+			if (cmd->flags & CXL_CMD_FLAG_FORCE_ENABLE)
+				set_bit(cmd->info.id, cxlm->enabled_cmds);
+
+		/* Found the required CEL */
+		rc = 0;
+	}
+
+out:
+	kvfree(gsl);
+	return rc;
+}
+
 /**
  * cxl_mem_identify() - Send the IDENTIFY command to the device.
  * @cxlm: The device to identify.
@@ -1266,6 +1471,10 @@ static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (rc)
 		return rc;
 
+	rc = cxl_mem_enumerate_cmds(cxlm);
+	if (rc)
+		return rc;
+
 	rc = cxl_mem_identify(cxlm);
 	if (rc)
 		return rc;

include/uapi/linux/cxl_mem.h

@@ -23,6 +23,7 @@
 	___C(INVALID, "Invalid Command"),                                 \
 	___C(IDENTIFY, "Identify Command"),                               \
 	___C(RAW, "Raw device command"),                                  \
+	___C(GET_SUPPORTED_LOGS, "Get Supported Logs"),                   \
 	___C(MAX, "invalid / last command")
 
 #define ___C(a, b) CXL_MEM_COMMAND_ID_##a