[focal:linux-azure][PATCH 1/1] Drivers: hv: vmbus: hibernation: do not hang forever in vmbus_bus_resume()

Marcelo Henrique Cerri marcelo.cerri at canonical.com
Fri Oct 23 20:39:43 UTC 2020

From: Dexuan Cui <decui at microsoft.com>

BugLink: https://bugs.launchpad.net/bugs/1894895

After we Stop and later Start a VM that uses Accelerated Networking (NIC
SR-IOV), currently the VF vmbus device's Instance GUID can change, so after
vmbus_bus_resume() -> vmbus_request_offers(), vmbus_onoffer() can not find
the original vmbus channel of the VF, and hence we can't complete()
vmbus_connection.ready_for_resume_event in check_ready_for_resume_event(),
and the VM hangs in vmbus_bus_resume() forever.

Fix the issue by adding a timeout, so the resuming can still succeed, and
the saved state is not lost, and according to my test, the user can disable
Accelerated Networking and then will be able to SSH into the VM for
further recovery. Also prevent the VM in question from suspending again.

The host will be fixed so in future the Instance GUID will stay the same
across hibernation.

Fixes: d8bd2d442bb2 ("Drivers: hv: vmbus: Resume after fixing up old primary channels")
Signed-off-by: Dexuan Cui <decui at microsoft.com>
Reviewed-by: Michael Kelley <mikelley at microsoft.com>
Link: https://lore.kernel.org/r/20200905025555.45614-1-decui@microsoft.com
Signed-off-by: Wei Liu <wei.liu at kernel.org>
(cherry picked from commit 19873eec7e13fda140a0ebc75d6664e57c00bfb1)
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>

That's a clean cherry-pick from upstream and I was able to reproduce
the issue and confirm it fixes the problem as described in the bug.

5.8 doesn't need the fix because it was already applied via upstream
stable updates.

 drivers/hv/vmbus_drv.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 42fa92b005df..847c652ad00e 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -2230,7 +2230,10 @@ static int vmbus_bus_suspend(struct device *dev)
 	if (atomic_read(&vmbus_connection.nr_chan_close_on_suspend) > 0)
-	WARN_ON(atomic_read(&vmbus_connection.nr_chan_fixup_on_resume) != 0);
+	if (atomic_read(&vmbus_connection.nr_chan_fixup_on_resume) != 0) {
+		pr_err("Can not suspend due to a previous failed resuming\n");
+		return -EBUSY;
+	}
@@ -2304,7 +2307,9 @@ static int vmbus_bus_resume(struct device *dev)
-	wait_for_completion(&vmbus_connection.ready_for_resume_event);
+	if (wait_for_completion_timeout(
+		&vmbus_connection.ready_for_resume_event, 10 * HZ) == 0)
+		pr_err("Some vmbus device is missing after suspending?\n");
 	/* Reset the event for the next suspend. */

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