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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Stephen Hemminger <stephen@networkplumber.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.15 098/124] uio_hv_generic: check that host
 supports monitor page
Thread-Topic: [PATCH AUTOSEL for 4.15 098/124] uio_hv_generic: check that host
 supports monitor page
Thread-Index: AQHTv5nFms+qtFW1mUW8+faI5OkGfQ==
Date:   Mon, 19 Mar 2018 15:48:49 +0000
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From: Stephen Hemminger <stephen@networkplumber.org>

[ 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>
---
 drivers/uio/uio_hv_generic.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index 48d5327d38d4..fe5cdda80b2c 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;
=20
+	/* 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 =3D -ENOTSUPP;
+		goto fail_close;
+	}
+
 	dev->channel->inbound.ring_buffer->interrupt_mask =3D 1;
 	set_channel_read_mode(dev->channel, HV_CALL_DIRECT);
=20
--=20
2.14.1