linux-kernel - [PATCH RFC v5 4/5] virtio: allow transports to suppress config change

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Message-ID: <bd9a6c26e03cafdc41a678c6eb12c0e91b7d0e69.1752094439.git.mst@redhat.com>
Date: Wed, 9 Jul 2025 16:55:33 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Lukas Wunner <lukas@...ner.de>, Keith Busch <kbusch@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Parav Pandit <parav@...dia.com>, virtualization@...ts.linux.dev,
	stefanha@...hat.com, alok.a.tiwari@...cle.com,
	Jason Wang <jasowang@...hat.com>,
	Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
	Eugenio Pérez <eperezma@...hat.com>
Subject: [PATCH RFC v5 4/5] virtio: allow transports to suppress config change

Will be used on surprise removal, so we don't need to
re-check.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/virtio/virtio.c | 18 +++++++++++++++++-
 include/linux/virtio.h  |  2 ++
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index c441c8cc71ef..1dd5cdf68c1d 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -127,7 +127,8 @@ static void __virtio_config_changed(struct virtio_device *dev)
 {
 	struct virtio_driver *drv = drv_to_virtio(dev->dev.driver);
 
-	if (!dev->config_core_enabled || dev->config_driver_disabled)
+	if (!dev->config_core_enabled || dev->config_driver_disabled ||
+	    dev->config_transport_disabled)
 		dev->config_change_pending = true;
 	else if (drv && drv->config_changed) {
 		drv->config_changed(dev);
@@ -193,6 +194,20 @@ static void virtio_config_core_enable(struct virtio_device *dev)
 	spin_unlock_irq(&dev->config_lock);
 }
 
+/**
+ * virtio_config_transport_disable - disable config change reporting by transport
+ * @dev: the device in question
+ *
+ * This must only be called by transport and enabling is not allowed.
+ */
+void virtio_config_transport_disable(struct virtio_device *dev)
+{
+	spin_lock_irq(&dev->config_lock);
+	dev->config_transport_disabled = true;
+	spin_unlock_irq(&dev->config_lock);
+}
+EXPORT_SYMBOL_GPL(virtio_config_transport_disable);
+
 void virtio_add_status(struct virtio_device *dev, unsigned int status)
 {
 	might_sleep();
@@ -530,6 +545,7 @@ int register_virtio_device(struct virtio_device *dev)
 		goto out_ida_remove;
 
 	spin_lock_init(&dev->config_lock);
+	dev->config_transport_disabled = false;
 	dev->config_driver_disabled = false;
 	dev->config_core_enabled = false;
 	dev->config_change_pending = false;
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index be0beb16b487..072a25f6622c 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -151,6 +151,7 @@ struct virtio_device {
 	bool failed;
 	u8 config_core_enabled:1;
 	u8 config_driver_disabled:1;
+	u8 config_transport_disabled:1;
 	u8 config_change_pending:1;
 	spinlock_t config_lock;
 	spinlock_t vqs_list_lock;
@@ -185,6 +186,7 @@ void virtio_config_changed(struct virtio_device *dev);
 void virtio_config_driver_disable(struct virtio_device *dev);
 void virtio_config_driver_enable(struct virtio_device *dev);
 
+void virtio_config_transport_disable(struct virtio_device *dev);
 #ifdef CONFIG_PM_SLEEP
 int virtio_device_freeze(struct virtio_device *dev);
 int virtio_device_restore(struct virtio_device *dev);
-- 
MST