virtio,pci,pc: features, fixes

[PULL 45/75] virtio: support irqfd in virtio_notify_config()

Michael S. Tsirkin posted 75 patches 1 month, 1 week ago

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Maintainers: "Michael S. Tsirkin" <mst@redhat.com>, Marcel Apfelbaum <marcel.apfelbaum@gmail.com>, Dongjiu Geng <gengdongjiu1@gmail.com>, Stefano Garzarella <sgarzare@redhat.com>, Igor Mammedov <imammedo@redhat.com>, Ani Sinha <anisinha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Mauro Carvalho Chehab <mchehab+huawei@kernel.org>, Shannon Zhao <shannon.zhaosl@gmail.com>, Peter Maydell <peter.maydell@linaro.org>, Stefan Hajnoczi <stefanha@redhat.com>, Kevin Wolf <kwolf@redhat.com>, Hanna Reitz <hreitz@redhat.com>, Eduardo Habkost <eduardo@habkost.net>, "Philippe Mathieu-Daudé" <philmd@linaro.org>, Yanan Wang <wangyanan55@huawei.com>, Zhao Liu <zhao1.liu@intel.com>, Richard Henderson <richard.henderson@linaro.org>, Jason Wang <jasowang@redhat.com>, Yi Liu <yi.l.liu@intel.com>, "Clément Mathieu--Drif" <clement.mathieu--drif@eviden.com>, Dmitry Fleytman <dmitry.fleytman@gmail.com>, Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>, Sriram Yagnaraman <sriram.yagnaraman@ericsson.com>, Keith Busch <kbusch@kernel.org>, Klaus Jensen <its@irrelevant.dk>, Jesper Devantier <foss@defmacro.it>, Fam Zheng <fam@euphon.net>, David Hildenbrand <david@redhat.com>, Cornelia Huck <cohuck@redhat.com>, Luigi Rizzo <rizzo@iet.unipi.it>, Giuseppe Lettieri <g.lettieri@iet.unipi.it>, Vincenzo Maffione <v.maffione@gmail.com>, Eric Blake <eblake@redhat.com>, Markus Armbruster <armbru@redhat.com>, Michael Roth <michael.roth@amd.com>, John Snow <jsnow@redhat.com>, Cleber Rosa <crosa@redhat.com>, Peter Xu <peterx@redhat.com>, Fabiano Rosas <farosas@suse.de>, Laurent Vivier <lvivier@redhat.com>

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[PULL 45/75] virtio: support irqfd in virtio_notify_config()

Posted by Michael S. Tsirkin 1 month, 1 week ago

From: Stefan Hajnoczi <stefanha@redhat.com>

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 <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-ID: <20250922220149.498967-4-stefanha@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 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 6ce5823898..de89e8104a 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2706,7 +2706,12 @@ void virtio_notify_config(VirtIODevice *vdev)
 
     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);
+    }
 }
 
 static bool virtio_device_endian_needed(void *opaque)
-- 
MST