[PATCH v2 3/4] cxl/uapi: Only return valid commands from cxl_query_cmd()

[Ira Weiny <ira.weiny@intel.com>]

It was pointed out that commands not supported by the device or excluded
by the kernel were being returned in cxl_query_cmd().[1]

While libcxl correctly handles failing commands, it is more efficient to
not issue an invalid command in the first place.

Exclude both kernel exclusive and disabled commands from the list of
commands returned by cxl_query_cmd().

[1] https://lore.kernel.org/all/63b4ec4e37cc1_5178e2941d@dwillia2-xfh.jf.intel.com.notmuch/

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>

---
Changes for v2:
	New patch
---
 drivers/cxl/core/mbox.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index b03fba212799..a1618b7f01e5 100644
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -326,12 +326,27 @@ static int cxl_to_mem_cmd_raw(struct cxl_mem_command *mem_cmd,
 	return 0;
 }
 
+/* Return 0 if the cmd id is available for userspace */
+static int cxl_cmd_id_user(__u32 id, struct cxl_dev_state *cxlds)
+{
+	/* Check that the command is enabled for hardware */
+	if (!test_bit(id, cxlds->enabled_cmds))
+		return -ENOTTY;
+
+	/* Check that the command is not claimed for exclusive kernel use */
+	if (test_bit(id, cxlds->exclusive_cmds))
+		return -EBUSY;
+
+	return 0;
+}
+
 static int cxl_to_mem_cmd(struct cxl_mem_command *mem_cmd,
 			  const struct cxl_send_command *send_cmd,
 			  struct cxl_dev_state *cxlds)
 {
 	struct cxl_mem_command *c = &cxl_mem_commands[send_cmd->id];
 	const struct cxl_command_info *info = &c->info;
+	int rc;
 
 	if (send_cmd->flags & ~CXL_MEM_COMMAND_FLAG_MASK)
 		return -EINVAL;
@@ -342,13 +357,9 @@ static int cxl_to_mem_cmd(struct cxl_mem_command *mem_cmd,
 	if (send_cmd->in.rsvd || send_cmd->out.rsvd)
 		return -EINVAL;
 
-	/* Check that the command is enabled for hardware */
-	if (!test_bit(info->id, cxlds->enabled_cmds))
-		return -ENOTTY;
-
-	/* Check that the command is not claimed for exclusive kernel use */
-	if (test_bit(info->id, cxlds->exclusive_cmds))
-		return -EBUSY;
+	rc = cxl_cmd_id_user(info->id, cxlds);
+	if (rc)
+		return rc;
 
 	/* Check the input buffer is the expected size */
 	if ((info->size_in != CXL_VARIABLE_PAYLOAD) &&
@@ -446,9 +457,15 @@ int cxl_query_cmd(struct cxl_memdev *cxlmd,
 	 */
 	cxl_for_each_cmd(cmd) {
 		const struct cxl_command_info *info = &cmd->info;
+		struct cxl_dev_state *cxlds = cxlmd->cxlds;
+		int rc;
 
-		if (copy_to_user(&q->commands[j++], info, sizeof(*info)))
-			return -EFAULT;
+		rc = cxl_cmd_id_user(info->id, cxlds);
+		if (!rc) {
+			if (copy_to_user(&q->commands[j++], info,
+					 sizeof(*info)))
+				return -EFAULT;
+		}
 
 		if (j == n_commands)
 			break;

-- 
2.39.1