From: Stephen Hemminger <stephen@networkplumber.org>
Date: Tue, 9 Jan 2018 20:57:31 +0000 (-0800)
Subject: uio_hv_generic: check that host supports monitor page
X-Git-Tag: v4.15.17~83
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3ca4e49e9be732841ea5fd44ce90db18e9855f65;p=thirdparty%2Fkernel%2Fstable.git

uio_hv_generic: check that host supports monitor page


[ Upstream commit 06028d15177a1b406b7b075ea47c6a352732f23a ]

In order for userspace application to signal host, it needs the
host to support the monitor page property. Check for the flag
and fail if this is not supported.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 48d5327d38d42..fe5cdda80b2ca 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -124,6 +124,13 @@ hv_uio_probe(struct hv_device *dev,
 	if (ret)
 		goto fail;
 
+	/* Communicating with host has to be via shared memory not hypercall */
+	if (!dev->channel->offermsg.monitor_allocated) {
+		dev_err(&dev->device, "vmbus channel requires hypercall\n");
+		ret = -ENOTSUPP;
+		goto fail_close;
+	}
+
 	dev->channel->inbound.ring_buffer->interrupt_mask = 1;
 	set_channel_read_mode(dev->channel, HV_CALL_DIRECT);