Re: [PATCH v3] virtio-pci: return IRQ_HANDLED after non-zero ISR
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2026-09-04 21:15:15
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On Fri, Sep 04, 2026 at 10:13:18AM -0400, Andrew Stellman wrote:
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: 77cf524654a8 ("virtio_pci: split up vp_interrupt")this is still the wrong commit to blame.
Suggested-by: Michael S. Tsirkin <mst@redhat.com> Assisted-by: LLM
This is not the correct format. See Documentation.
quoted hunk ↗ jump to hunk
Signed-off-by: Andrew Stellman <redacted> --- Changes from v2: - Repost as a standalone patch in a new thread, per maintainer request. - Add LLM-assistance disclosure. - No code changes. Changes from v1: - Return IRQ_HANDLED for any non-zero ISR, as suggested by Michael. - Add Fixes and Suggested-by tags. - Test the change with virtio-blk forced to legacy INTx under QEMU. Full red/green test logs and the tested v2 patch: https://github.com/andrewstellman/quality-playbook/tree/11ba61d/evidence/virtio-pci-intx drivers/virtio/virtio_pci_common.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c index 10371ecbc054..b90c174450b2 100644 --- a/drivers/virtio/virtio_pci_common.c +++ b/drivers/virtio/virtio_pci_common.c@@ -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,base-commit: bc35965f6940a9bf834d54187b6088b8eb09206d
I already did exactly this in my tree, no further action is necessary, but I will add your tested by tag. Thanks!
-- 2.43.0