Drivers: hv: vmbus: Use all supported IC versions to negotiate

Previously, we were assuming that each IC protocol version was tied to a
specific host version. For example, some Windows 10 preview hosts only
support v3 TimeSync even though driver assumes v4 is supported by all
Windows 10 hosts.

The guest will stop trying to negotiate even though older supported
versions may still be offered by the host.

Make IC version negotiation more robust by going through all versions
that are supported by the guest.

Fixes: 3da0401b4d0e ("Drivers: hv: utils: Fix the mapping between host
version and protocol to use")

Reported-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Signed-off-by: Alex Ng <alexng@messages.microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 54 insertions, 26 deletions

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index 49d77be90ca4..de90a9900fee 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -204,33 +204,34 @@ static u16 hv_get_dev_type(const struct vmbus_channel *channel)
  * @buf: Raw buffer channel data
  *
  * @icmsghdrp is of type &struct icmsg_hdr.
- * @negop is of type &struct icmsg_negotiate.
  * Set up and fill in default negotiate response message.
  *
- * The fw_version specifies the  framework version that
- * we can support and srv_version specifies the service
- * version we can support.
+ * The fw_version and fw_vercnt specifies the framework version that
+ * we can support.
+ *
+ * The srv_version and srv_vercnt specifies the service
+ * versions we can support.
+ *
+ * Versions are given in decreasing order.
+ *
+ * nego_fw_version and nego_srv_version store the selected protocol versions.
  *
  * Mainly used by Hyper-V drivers.
  */
 bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
-				struct icmsg_negotiate *negop, u8 *buf,
-				int fw_version, int srv_version)
+				u8 *buf, const int *fw_version, int fw_vercnt,
+				const int *srv_version, int srv_vercnt,
+				int *nego_fw_version, int *nego_srv_version)
 {
 	int icframe_major, icframe_minor;
 	int icmsg_major, icmsg_minor;
 	int fw_major, fw_minor;
 	int srv_major, srv_minor;
-	int i;
+	int i, j;
 	bool found_match = false;
+	struct icmsg_negotiate *negop;
 
 	icmsghdrp->icmsgsize = 0x10;
-	fw_major = (fw_version >> 16);
-	fw_minor = (fw_version & 0xFFFF);
-
-	srv_major = (srv_version >> 16);
-	srv_minor = (srv_version & 0xFFFF);
-
 	negop = (struct icmsg_negotiate *)&buf[
 		sizeof(struct vmbuspipe_hdr) +
 		sizeof(struct icmsg_hdr)];
@@ -246,13 +247,22 @@ bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
 	 * support.
 	 */
 
-	for (i = 0; i < negop->icframe_vercnt; i++) {
-		if ((negop->icversion_data[i].major == fw_major) &&
-		   (negop->icversion_data[i].minor == fw_minor)) {
-			icframe_major = negop->icversion_data[i].major;
-			icframe_minor = negop->icversion_data[i].minor;
-			found_match = true;
+	for (i = 0; i < fw_vercnt; i++) {
+		fw_major = (fw_version[i] >> 16);
+		fw_minor = (fw_version[i] & 0xFFFF);
+
+		for (j = 0; j < negop->icframe_vercnt; j++) {
+			if ((negop->icversion_data[j].major == fw_major) &&
+			    (negop->icversion_data[j].minor == fw_minor)) {
+				icframe_major = negop->icversion_data[j].major;
+				icframe_minor = negop->icversion_data[j].minor;
+				found_match = true;
+				break;
+			}
 		}
+
+		if (found_match)
+			break;
 	}
 
 	if (!found_match)
@@ -260,14 +270,26 @@ bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
 
 	found_match = false;
 
-	for (i = negop->icframe_vercnt;
-		 (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) {
-		if ((negop->icversion_data[i].major == srv_major) &&
-		   (negop->icversion_data[i].minor == srv_minor)) {
-			icmsg_major = negop->icversion_data[i].major;
-			icmsg_minor = negop->icversion_data[i].minor;
-			found_match = true;
+	for (i = 0; i < srv_vercnt; i++) {
+		srv_major = (srv_version[i] >> 16);
+		srv_minor = (srv_version[i] & 0xFFFF);
+
+		for (j = negop->icframe_vercnt;
+			(j < negop->icframe_vercnt + negop->icmsg_vercnt);
+			j++) {
+
+			if ((negop->icversion_data[j].major == srv_major) &&
+				(negop->icversion_data[j].minor == srv_minor)) {
+
+				icmsg_major = negop->icversion_data[j].major;
+				icmsg_minor = negop->icversion_data[j].minor;
+				found_match = true;
+				break;
+			}
 		}
+
+		if (found_match)
+			break;
 	}
 
 	/*
@@ -284,6 +306,12 @@ fw_error:
 		negop->icmsg_vercnt = 1;
 	}
 
+	if (nego_fw_version)
+		*nego_fw_version = (icframe_major << 16) | icframe_minor;
+
+	if (nego_srv_version)
+		*nego_srv_version = (icmsg_major << 16) | icmsg_minor;
+
 	negop->icversion_data[0].major = icframe_major;
 	negop->icversion_data[0].minor = icframe_minor;
 	negop->icversion_data[1].major = icmsg_major;