Drivers: hv: Support handling multiple VMBUS versions

The current code hard coded the vmbus version independent of the host
it was running on. Add code to dynamically negotiate the most appropriate
version.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 111 insertions, 60 deletions

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index d1019a770ad..2b56a3f47b3 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -40,15 +40,111 @@ struct vmbus_connection vmbus_connection = {
 };
 
 /*
+ * VMBUS version is 32 bit entity broken up into
+ * two 16 bit quantities: major_number. minor_number.
+ *
+ * 0 . 13 (Windows Server 2008)
+ * 1 . 1  (Windows 7)
+ * 2 . 4  (Windows 8)
+ */
+
+#define VERSION_WS2008	((0 << 16) | (13))
+#define VERSION_WIN7	((1 << 16) | (1))
+#define VERSION_WIN8	((2 << 16) | (4))
+
+#define VERSION_INVAL -1
+
+static __u32 vmbus_get_next_version(__u32 current_version)
+{
+	switch (current_version) {
+	case (VERSION_WIN7):
+		return VERSION_WS2008;
+
+	case (VERSION_WIN8):
+		return VERSION_WIN7;
+
+	case (VERSION_WS2008):
+	default:
+		return VERSION_INVAL;
+	}
+}
+
+static int vmbus_negotiate_version(struct vmbus_channel_msginfo *msginfo,
+					__u32 version)
+{
+	int ret = 0;
+	struct vmbus_channel_initiate_contact *msg;
+	unsigned long flags;
+	int t;
+
+	init_completion(&msginfo->waitevent);
+
+	msg = (struct vmbus_channel_initiate_contact *)msginfo->msg;
+
+	msg->header.msgtype = CHANNELMSG_INITIATE_CONTACT;
+	msg->vmbus_version_requested = version;
+	msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
+	msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages);
+	msg->monitor_page2 = virt_to_phys(
+			(void *)((unsigned long)vmbus_connection.monitor_pages +
+				 PAGE_SIZE));
+
+	/*
+	 * Add to list before we send the request since we may
+	 * receive the response before returning from this routine
+	 */
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+	list_add_tail(&msginfo->msglistentry,
+		      &vmbus_connection.chn_msg_list);
+
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+
+	ret = vmbus_post_msg(msg,
+			       sizeof(struct vmbus_channel_initiate_contact));
+	if (ret != 0) {
+		spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+		list_del(&msginfo->msglistentry);
+		spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
+					flags);
+		return ret;
+	}
+
+	/* Wait for the connection response */
+	t =  wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
+	if (t == 0) {
+		spin_lock_irqsave(&vmbus_connection.channelmsg_lock,
+				flags);
+		list_del(&msginfo->msglistentry);
+		spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
+					flags);
+		return -ETIMEDOUT;
+	}
+
+	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
+	list_del(&msginfo->msglistentry);
+	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+
+	/* Check if successful */
+	if (msginfo->response.version_response.version_supported) {
+		vmbus_connection.conn_state = CONNECTED;
+	} else {
+		pr_err("Unable to connect, "
+			"Version %d not supported by Hyper-V\n",
+			version);
+		return -ECONNREFUSED;
+	}
+
+	return ret;
+}
+
+/*
  * vmbus_connect - Sends a connect request on the partition service connection
  */
 int vmbus_connect(void)
 {
 	int ret = 0;
-	int t;
 	struct vmbus_channel_msginfo *msginfo = NULL;
-	struct vmbus_channel_initiate_contact *msg;
-	unsigned long flags;
+	__u32 version;
 
 	/* Initialize the vmbus connection */
 	vmbus_connection.conn_state = CONNECTING;
@@ -99,64 +195,25 @@ int vmbus_connect(void)
 		goto cleanup;
 	}
 
-	init_completion(&msginfo->waitevent);
-
-	msg = (struct vmbus_channel_initiate_contact *)msginfo->msg;
-
-	msg->header.msgtype = CHANNELMSG_INITIATE_CONTACT;
-	msg->vmbus_version_requested = VMBUS_REVISION_NUMBER;
-	msg->interrupt_page = virt_to_phys(vmbus_connection.int_page);
-	msg->monitor_page1 = virt_to_phys(vmbus_connection.monitor_pages);
-	msg->monitor_page2 = virt_to_phys(
-			(void *)((unsigned long)vmbus_connection.monitor_pages +
-				 PAGE_SIZE));
-
 	/*
-	 * Add to list before we send the request since we may
-	 * receive the response before returning from this routine
+	 * Negotiate a compatible VMBUS version number with the
+	 * host. We start with the highest number we can support
+	 * and work our way down until we negotiate a compatible
+	 * version.
 	 */
-	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
-	list_add_tail(&msginfo->msglistentry,
-		      &vmbus_connection.chn_msg_list);
-
-	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 
-	ret = vmbus_post_msg(msg,
-			       sizeof(struct vmbus_channel_initiate_contact));
-	if (ret != 0) {
-		spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
-		list_del(&msginfo->msglistentry);
-		spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
-					flags);
-		goto cleanup;
-	}
+	version = VERSION_WS2008;
 
-	/* Wait for the connection response */
-	t =  wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
-	if (t == 0) {
-		spin_lock_irqsave(&vmbus_connection.channelmsg_lock,
-				flags);
-		list_del(&msginfo->msglistentry);
-		spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock,
-					flags);
-		ret = -ETIMEDOUT;
-		goto cleanup;
-	}
+	do {
+		ret = vmbus_negotiate_version(msginfo, version);
+		if (ret == 0)
+			break;
 
-	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
-	list_del(&msginfo->msglistentry);
-	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
+		version = vmbus_get_next_version(version);
+	} while (version != VERSION_INVAL);
 
-	/* Check if successful */
-	if (msginfo->response.version_response.version_supported) {
-		vmbus_connection.conn_state = CONNECTED;
-	} else {
-		pr_err("Unable to connect, "
-			"Version %d not supported by Hyper-V\n",
-			VMBUS_REVISION_NUMBER);
-		ret = -ECONNREFUSED;
+	if (version == VERSION_INVAL)
 		goto cleanup;
-	}
 
 	kfree(msginfo);
 	return 0;
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 1ffe84de6c5..b097bf9d932 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -406,12 +406,6 @@ hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,
 #define HV_DRV_VERSION           "3.1"
 
 
-/*
- * A revision number of vmbus that is used for ensuring both ends on a
- * partition are using compatible versions.
- */
-#define VMBUS_REVISION_NUMBER		13
-
 /* Make maximum size of pipe payload of 16K */
 #define MAX_PIPE_DATA_PAYLOAD		(sizeof(u8) * 16384)