[PATCH 3/4] virtio-pci: return IRQ_HANDLED for config-change interrupts

[Andrew Stellman <astellman@stellman-greene.com>]

vp_interrupt() unconditionally returns the result of
vp_vring_interrupt(). When a config-change interrupt fires but no vring
activity is pending, vp_vring_interrupt() returns IRQ_NONE — even
though the interrupt was legitimately handled by vp_config_changed().
Over time this causes the IRQ subsystem to flag the line as spurious.

Track the return value explicitly: set ret to IRQ_HANDLED when the
config-change bit is set, OR it with the vring result, and return the
combined value.

Signed-off-by: Andrew Stellman <astellman@stellman-greene.com>
---
 drivers/virtio/virtio_pci_common.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 0b9d66b..1d1ab02 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -106,6 +106,7 @@ static irqreturn_t vp_vring_interrupt(int irq, void *opaque)
 static irqreturn_t vp_interrupt(int irq, void *opaque)
 {
 	struct virtio_pci_device *vp_dev = opaque;
+	irqreturn_t ret = IRQ_NONE;
 	u8 isr;
 
 	/* reading the ISR has the effect of also clearing it so it's very
@@ -117,10 +118,15 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
 		return IRQ_NONE;
 
 	/* Configuration change?  Tell driver if it wants to know. */
-	if (isr & VIRTIO_PCI_ISR_CONFIG)
+	if (isr & VIRTIO_PCI_ISR_CONFIG) {
 		vp_config_changed(irq, opaque);
+		ret = IRQ_HANDLED;
+	}
 
-	return vp_vring_interrupt(irq, opaque);
+	if (vp_vring_interrupt(irq, opaque) == IRQ_HANDLED)
+		ret = IRQ_HANDLED;
+
+	return ret;
 }
 
 static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
-- 
2.34.1