cxl/mbox: Make handle_mailbox_cmd_from_user() use a mbox param

Previously, handle_mailbox_cmd_from_user(), constructed the mailbox
command and dispatched it to the hardware. The construction work
has moved to the validation path.

handle_mailbox_cmd_from_user() now expects a fully validated
mbox param. Make it's caller, cxl_send_cmd(), deliver it. Update
the comments and dereferencing of the new mbox parameter.
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/77050ba512d6c30eccf7505467509e460dd325a0.1648687552.git.alison.schofield@intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/mbox.c

@@ -423,8 +423,7 @@ int cxl_query_cmd(struct cxl_memdev *cxlmd,
 /**
  * handle_mailbox_cmd_from_user() - Dispatch a mailbox command for userspace.
  * @cxlds: The device data for the operation
- * @cmd: The validated command.
- * @in_payload: Pointer to userspace's input payload.
+ * @mbox_cmd: The validated mailbox command.
  * @out_payload: Pointer to userspace's output payload.
  * @size_out: (Input) Max payload size to copy out.
  *            (Output) Payload size hardware generated.
@@ -439,35 +438,27 @@ int cxl_query_cmd(struct cxl_memdev *cxlmd,
  *  * %-EINTR	- Mailbox acquisition interrupted.
  *  * %-EXXX	- Transaction level failures.
  *
- * Creates the appropriate mailbox command and dispatches it on behalf of a
- * userspace request. The input and output payloads are copied between
- * userspace.
+ * Dispatches a mailbox command on behalf of a userspace request.
+ * The output payload is copied to userspace.
  *
  * See cxl_send_cmd().
  */
 static int handle_mailbox_cmd_from_user(struct cxl_dev_state *cxlds,
-					const struct cxl_mem_command *cmd,
-					u64 in_payload, u64 out_payload,
-					s32 *size_out, u32 *retval)
+					struct cxl_mbox_cmd *mbox_cmd,
+					u64 out_payload, s32 *size_out,
+					u32 *retval)
 {
 	struct device *dev = cxlds->dev;
-	struct cxl_mbox_cmd mbox_cmd;
 	int rc;
 
-	rc = cxl_mbox_cmd_ctor(&mbox_cmd, cxlds, cmd->opcode,
-			       cmd->info.size_in, cmd->info.size_out,
-			       in_payload);
-	if (rc)
-		return rc;
-
 	dev_dbg(dev,
 		"Submitting %s command for user\n"
 		"\topcode: %x\n"
 		"\tsize: %zx\n",
-		cxl_mem_opcode_to_name(mbox_cmd.opcode),
-		mbox_cmd.opcode, mbox_cmd.size_in);
+		cxl_mem_opcode_to_name(mbox_cmd->opcode),
+		mbox_cmd->opcode, mbox_cmd->size_in);
 
-	rc = cxlds->mbox_send(cxlds, &mbox_cmd);
+	rc = cxlds->mbox_send(cxlds, mbox_cmd);
 	if (rc)
 		goto out;
 
@@ -476,21 +467,21 @@ static int handle_mailbox_cmd_from_user(struct cxl_dev_state *cxlds,
 	 * to userspace. While the payload may have written more output than
 	 * this it will have to be ignored.
 	 */
-	if (mbox_cmd.size_out) {
-		dev_WARN_ONCE(dev, mbox_cmd.size_out > *size_out,
+	if (mbox_cmd->size_out) {
+		dev_WARN_ONCE(dev, mbox_cmd->size_out > *size_out,
 			      "Invalid return size\n");
 		if (copy_to_user(u64_to_user_ptr(out_payload),
-				 mbox_cmd.payload_out, mbox_cmd.size_out)) {
+				 mbox_cmd->payload_out, mbox_cmd->size_out)) {
 			rc = -EFAULT;
 			goto out;
 		}
 	}
 
-	*size_out = mbox_cmd.size_out;
-	*retval = mbox_cmd.return_code;
+	*size_out = mbox_cmd->size_out;
+	*retval = mbox_cmd->return_code;
 
 out:
-	cxl_mbox_cmd_dtor(&mbox_cmd);
+	cxl_mbox_cmd_dtor(mbox_cmd);
 	return rc;
 }
 
@@ -512,9 +503,8 @@ int cxl_send_cmd(struct cxl_memdev *cxlmd, struct cxl_send_command __user *s)
 	if (rc)
 		return rc;
 
-	rc = handle_mailbox_cmd_from_user(cxlds, &c, send.in.payload,
-					  send.out.payload, &send.out.size,
-					  &send.retval);
+	rc = handle_mailbox_cmd_from_user(cxlds, &mbox_cmd, send.out.payload,
+					  &send.out.size, &send.retval);
 	if (rc)
 		return rc;