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Fri, 04 Sep 2026 07:13:25 -0700 (PDT) Received: from Mac.mynetworksettings.com ([2600:4041:5c28:200:bc26:3e94:1d7f:e1ff]) by smtp.gmail.com with ESMTPSA id af79cd13be357-9397faf927bsm217736285a.8.2026.09.04.07.13.24 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Fri, 04 Sep 2026 07:13:24 -0700 (PDT) Sender: Andrew Stellman From: Andrew Stellman To: mst@redhat.com Cc: jasowangio@gmail.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, astellman@stellman-greene.com Subject: [PATCH v3] virtio-pci: return IRQ_HANDLED after non-zero ISR Date: Fri, 4 Sep 2026 10:13:18 -0400 Message-ID: <20260904141318.30278-1-astellman@stellman-greene.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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=3D0 and pci=3Dnomsi. On an idle device, 200 config-change interrupts were generated using QMP block_resize. Before this change, irq_handler_exit reported ret=3Dunhandled and /proc/irq/11/spurious increased from 0 to 200 unhandled interrupts. After this change, irq_handler_exit reported ret=3Dhandled 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") Suggested-by: Michael S. Tsirkin Assisted-by: LLM Signed-off-by: Andrew Stellman --- 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/vi= rtio-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); =20 - return vp_vring_interrupt(irq, opaque); + vp_vring_interrupt(irq, opaque); + + return IRQ_HANDLED; } =20 static int vp_request_msix_vectors(struct virtio_device *vdev, int nvector= s, base-commit: bc35965f6940a9bf834d54187b6088b8eb09206d --=20 2.43.0