Drivers: hv: vss: run only on supported host versions

The Backup integration service on WS2012 has appearently trouble to
negotiate with a guest which does not support the provided util version.
Currently the VSS driver supports only version 5/0. A WS2012 offers only
version 1/x and 3/x, and vmbus_prep_negotiate_resp correctly returns an
empty icframe_vercnt/icmsg_vercnt. But the host ignores that and
continues to send ICMSGTYPE_NEGOTIATE messages. The result are weird
errors during boot and general misbehaviour.

Check the Windows version to work around the host bug, skip hv_vss_init
on WS2012 and older.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/hv_snapshot.c b/drivers/hv/hv_snapshot.c
index a548ae42c927a8ffdb7305e692c5615e05678964..81882d4848bdf1f29f1d26e86bd27f49b3ddb206 100644 (file)
--- a/drivers/hv/hv_snapshot.c
+++ b/drivers/hv/hv_snapshot.c
@@ -331,6 +331,11 @@ static void vss_on_reset(void)
 int
 hv_vss_init(struct hv_util_service *srv)
 {
+       if (vmbus_proto_version < VERSION_WIN8_1) {
+               pr_warn("Integration service 'Backup (volume snapshot)'"
+                       " not supported on this host version.\n");
+               return -ENOTSUPP;
+       }
        recv_buffer = srv->recv_buffer;
 
        /*