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virtio-pci: return IRQ_HANDLED after non-zero ISR

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vp_interrupt() reads the ISR before dispatching config-change and
vring handling. Reading the ISR also clears it, so once the read
returns non-zero the interrupt was from this device and has already
been consumed.

Currently vp_interrupt() returns the result of vp_vring_interrupt().
For a config-change interrupt with no vring work, that can return
IRQ_NONE even though the ISR was non-zero and the interrupt was
handled.

Call vp_vring_interrupt() for any queue work, but once the ISR is
non-zero return IRQ_HANDLED.

Tested with QEMU virtio-blk-pci forced to INTx using vectors=0 and
pci=nomsi. On an idle device, 200 config-change interrupts were
generated using QMP block_resize.

Before this change, irq_handler_exit reported ret=unhandled and
/proc/irq/11/spurious increased from 0 to 200 unhandled interrupts.
After this change, irq_handler_exit reported ret=handled and the
unhandled count remained at 0.

The issue was found during an LLM-assisted Quality Playbook review.

Fixes: 77cf524654 ("virtio_pci: split up vp_interrupt")
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Assisted-by: LLM
Signed-off-by: Andrew Stellman <astellman@stellman-greene.com>
Message-ID: <20260904141318.30278-1-astellman@stellman-greene.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Andrew Stellman 2026-09-04 10:13:18 -04:00 committed by Michael S. Tsirkin
parent 8dd505a45d
commit 93fa09455f
1 changed files with 3 additions and 1 deletions
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4
drivers/virtio/virtio_pci_common.c
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@ -120,7 +120,9 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
if (isr & VIRTIO_PCI_ISR_CONFIG)
vp_config_changed(irq, opaque);
return vp_vring_interrupt(irq, opaque);
vp_vring_interrupt(irq, opaque);
return IRQ_HANDLED;
}
static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,