[PATCH v2 10/11] uio_hv_generic: add rescind support

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When host rescinds the device, the UIO driver will clear the interrupt
state and notify application. The read (or write) on the interrupt FD
will then fail with -EIO. This is simpler than adding lots extra uevent
stuff inside UIO.

Signed-off-by: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
---
 Documentation/driver-api/uio-howto.rst |  4 ++++
 drivers/uio/uio_hv_generic.c           | 19 +++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/Documentation/driver-api/uio-howto.rst b/Documentation/driver-api/uio-howto.rst
index a4228e371244..0030de9205fd 100644
--- a/Documentation/driver-api/uio-howto.rst
+++ b/Documentation/driver-api/uio-howto.rst
@@ -698,6 +698,10 @@ prevents the device from generating further interrupts until the bit is
 cleared. The userspace driver should clear this bit before blocking and
 waiting for more interrupts.
 
+When host rescinds a device, the interrupt file descriptor is marked down
+and any reads of the interrupt file descriptor will return -EIO. Similar
+to a closed socket or disconnected serial device.
+
 The vmbus device regions are mapped into uio device resources.
     0) Channel ring buffers: guest to host and host to guest
     1) Guest to host interrupt signalling pages
diff --git a/drivers/uio/uio_hv_generic.c b/drivers/uio/uio_hv_generic.c
index b5fe0db844a7..eab173665dd4 100644
--- a/drivers/uio/uio_hv_generic.c
+++ b/drivers/uio/uio_hv_generic.c
@@ -115,6 +115,23 @@ static void hv_uio_channel_cb(void *context)
 	uio_event_notify(&pdata->info);
 }
 
+/*
+ * Callback from vmbus_event when channel is rescinded.
+ */
+static void hv_uio_rescind(struct vmbus_channel *channel)
+{
+	struct hv_device *hv_dev = channel->primary_channel->device_obj;
+	struct hv_uio_private_data *pdata = hv_get_drvdata(hv_dev);
+
+	/*
+	 * Turn off the interrupt file handle
+	 * Next read for event will return -EIO
+	 */
+	pdata->info.irq = 0;
+
+	/* Wake up reader */
+	uio_event_notify(&pdata->info);
+}
 
 static void
 hv_uio_cleanup(struct hv_device *dev, struct hv_uio_private_data *pdata)
@@ -248,6 +265,8 @@ hv_uio_probe(struct hv_device *dev,
 		goto fail_cleanup;
 	}
 
+	vmbus_set_chn_rescind_callback(dev->channel, hv_uio_rescind);
+
 	hv_set_drvdata(dev, pdata);
 
 	return 0;
-- 
2.15.1

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