linux-kernel - [PATCH 2/2] vfio-pci: Log device requests more verbosely

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Date:	Tue, 14 Apr 2015 12:14:51 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	alex.williamson@...hat.com
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH 2/2] vfio-pci: Log device requests more verbosely

Log some clues indicating whether the user is receiving device
request interfaces or not listening.  This can help indicate why a
driver unbind is blocked or explain why QEMU automatically unplugged
a device from the VM.

Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---
 drivers/vfio/pci/vfio_pci.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index d9f7ec5..5eb9cbe 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -923,8 +923,14 @@ static void vfio_pci_request(void *device_data, unsigned int count)
 	mutex_lock(&vdev->igate);
 
 	if (vdev->req_trigger) {
-		dev_dbg(&vdev->pdev->dev, "Requesting device from user\n");
+		if (!(count % 10))
+			dev_notice_ratelimited(&vdev->pdev->dev,
+				"Relaying device request to user (#%u)\n",
+				count);
 		eventfd_signal(vdev->req_trigger, 1);
+	} else if (count == 0) {
+		dev_warn(&vdev->pdev->dev,
+			"No device request channel registered, blocked until released by user\n");
 	}
 
 	mutex_unlock(&vdev->igate);

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