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Tsirkin" , , Hanna Reitz , Laurent Vivier , Fam Zheng , Fabiano Rosas , Paolo Bonzini , Stefan Hajnoczi , Stefano Garzarella Subject: [PATCH 3/5] virtio: support irqfd in virtio_notify_config() Date: Mon, 22 Sep 2025 18:01:47 -0400 Message-ID: <20250922220149.498967-4-stefanha@redhat.com> In-Reply-To: <20250922220149.498967-1-stefanha@redhat.com> References: <20250922220149.498967-1-stefanha@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=170.10.129.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.442, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @redhat.com) X-ZM-MESSAGEID: 1758578588309116600 Content-Type: text/plain; charset="utf-8" virtio_error() calls virtio_notify_config() to inject a VIRTIO Configuration Change Notification. This doesn't work from IOThreads because the BQL is not held and the interrupt code path requires the BQL. Follow the same approach as virtio_notify() and use ->config_notifier (an irqfd) when called from the IOThread. Signed-off-by: Stefan Hajnoczi --- hw/virtio/virtio.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 13830debfd..ced0fea4fc 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2706,7 +2706,12 @@ void virtio_notify_config(VirtIODevice *vdev) =20 virtio_set_isr(vdev, 0x3); vdev->generation++; - virtio_notify_vector(vdev, vdev->config_vector); + + if (qemu_in_iothread()) { + defer_call(virtio_notify_irqfd_deferred_fn, &vdev->config_notifier= ); + } else { + virtio_notify_vector(vdev, vdev->config_vector); + } } =20 static bool virtio_device_endian_needed(void *opaque) --=20 2.51.0