habanalabs: leave space for 2xMSG_PROT in CB

The user must leave space for 2xMSG_PROT in the external CB, so adjust the
define of max size accordingly. The driver, however, can still create a CB
with the maximum size of 2MB. Therefore, we need to add a check
specifically for the user requested size.
Reviewed-by: Tomer Tayar <ttayar@habana.ai>
Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>

drivers/misc/habanalabs/command_buffer.c

@@ -105,10 +105,9 @@ int hl_cb_create(struct hl_device *hdev, struct hl_cb_mgr *mgr,
 		goto out_err;
 	}
 
-	if (cb_size > HL_MAX_CB_SIZE) {
-		dev_err(hdev->dev,
-			"CB size %d must be less then %d\n",
-			cb_size, HL_MAX_CB_SIZE);
+	if (cb_size > SZ_2M) {
+		dev_err(hdev->dev, "CB size %d must be less than %d\n",
+			cb_size, SZ_2M);
 		rc = -EINVAL;
 		goto out_err;
 	}
@@ -211,7 +210,7 @@ int hl_cb_ioctl(struct hl_fpriv *hpriv, void *data)
 {
 	union hl_cb_args *args = data;
 	struct hl_device *hdev = hpriv->hdev;
-	u64 handle;
+	u64 handle = 0;
 	int rc;
 
 	if (hl_device_disabled_or_in_reset(hdev)) {
@@ -223,15 +222,26 @@ int hl_cb_ioctl(struct hl_fpriv *hpriv, void *data)
 
 	switch (args->in.op) {
 	case HL_CB_OP_CREATE:
-		rc = hl_cb_create(hdev, &hpriv->cb_mgr, args->in.cb_size,
-					&handle, hpriv->ctx->asid);
+		if (args->in.cb_size > HL_MAX_CB_SIZE) {
+			dev_err(hdev->dev,
+				"User requested CB size %d must be less than %d\n",
+				args->in.cb_size, HL_MAX_CB_SIZE);
+			rc = -EINVAL;
+		} else {
+			rc = hl_cb_create(hdev, &hpriv->cb_mgr,
+						args->in.cb_size, &handle,
+						hpriv->ctx->asid);
+		}
+
 		memset(args, 0, sizeof(*args));
 		args->out.cb_handle = handle;
 		break;
+
 	case HL_CB_OP_DESTROY:
 		rc = hl_cb_destroy(hdev, &hpriv->cb_mgr,
 					args->in.cb_handle);
 		break;
+
 	default:
 		rc = -ENOTTY;
 		break;

include/uapi/misc/habanalabs.h

@@ -209,7 +209,8 @@ struct hl_info_args {
 /* Opcode to destroy previously created command buffer */
 #define HL_CB_OP_DESTROY	1
 
-#define HL_MAX_CB_SIZE		0x200000	/* 2MB */
+/* 2MB minus 32 bytes for 2xMSG_PROT */
+#define HL_MAX_CB_SIZE		(0x200000 - 32)
 
 struct hl_cb_in {
 	/* Handle of CB or 0 if we want to create one */