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[80.230.79.236]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49d07b371afsm242068095e9.9.2026.09.07.14.45.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Sep 2026 14:45:40 -0700 (PDT) Date: Mon, 7 Sep 2026 17:45:37 -0400 From: "Michael S. Tsirkin" To: Andrew Stellman Cc: jasowangio@gmail.com, xuanzhuo@linux.alibaba.com, eperezma@redhat.com, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] virtio-pci: return IRQ_HANDLED after non-zero ISR Message-ID: <20260907174523-mutt-send-email-mst@kernel.org> References: <20260904141318.30278-1-astellman@stellman-greene.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260904141318.30278-1-astellman@stellman-greene.com> 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") > Suggested-by: Michael S. Tsirkin > Assisted-by: LLM tell us which llm and which agent pls > 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/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 > > -- > 2.43.0