[PATCH 7/7] um: virtio/pci: enable suspend/resume

[Johannes Berg]

From: Johannes Berg <johannes.berg@xxxxxxxxx>

The UM virtual PCI devices currently cannot be suspended properly
since the virtio driver already disables VQs well before the PCI
bus's suspend_noirq wants to complete the transition by writing to
PCI config space.

After trying around for a long time with moving the devices on the
DPM list, trying to create dependencies between them, etc. I gave
up and instead added UML specific cross-driver API that lets the
virt-pci code enable not suspending/resuming VQs for its devices.

This then allows the PCI bus suspend_noirq to still talk to the
device, and suspend/resume works properly.

Signed-off-by: Johannes Berg <johannes.berg@xxxxxxxxx>
---
 arch/um/drivers/virt-pci.c         |  7 ++++++
 arch/um/drivers/virtio_uml.c       | 40 ++++++++++++++++++++++--------
 arch/um/include/linux/virtio-uml.h | 13 ++++++++++
 3 files changed, 50 insertions(+), 10 deletions(-)
 create mode 100644 arch/um/include/linux/virtio-uml.h

diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
index dd85f36197aa..e5d57ec8ada6 100644
--- a/arch/um/drivers/virt-pci.c
+++ b/arch/um/drivers/virt-pci.c
@@ -10,6 +10,7 @@
 #include <linux/logic_iomem.h>
 #include <linux/irqdomain.h>
 #include <linux/virtio_pcidev.h>
+#include <linux/virtio-uml.h>
 #include <linux/delay.h>
 #include <linux/msi.h>
 #include <asm/unaligned.h>
@@ -550,6 +551,12 @@ static int um_pci_virtio_probe(struct virtio_device *vdev)
 
 	device_set_wakeup_enable(&vdev->dev, true);
 
+	/*
+	 * In order to do suspend-resume properly, don't allow VQs
+	 * to be suspended.
+	 */
+	virtio_uml_set_no_vq_suspend(vdev, true);
+
 	um_pci_rescan();
 	return 0;
 error:
diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
index 91ddf74ca888..4412d6febade 100644
--- a/arch/um/drivers/virtio_uml.c
+++ b/arch/um/drivers/virtio_uml.c
@@ -56,6 +56,7 @@ struct virtio_uml_device {
 	u8 status;
 	u8 registered:1;
 	u8 suspended:1;
+	u8 no_vq_suspend:1;
 
 	u8 config_changed_irq:1;
 	uint64_t vq_irq_vq_map;
@@ -1098,6 +1099,19 @@ static void virtio_uml_release_dev(struct device *d)
 	kfree(vu_dev);
 }
 
+void virtio_uml_set_no_vq_suspend(struct virtio_device *vdev,
+				  bool no_vq_suspend)
+{
+	struct virtio_uml_device *vu_dev = to_virtio_uml_device(vdev);
+
+	if (WARN_ON(vdev->config != &virtio_uml_config_ops))
+		return;
+
+	vu_dev->no_vq_suspend = no_vq_suspend;
+	dev_info(&vdev->dev, "%sabled VQ suspend\n",
+		 no_vq_suspend ? "dis" : "en");
+}
+
 /* Platform device */
 
 static int virtio_uml_probe(struct platform_device *pdev)
@@ -1302,13 +1316,16 @@ MODULE_DEVICE_TABLE(of, virtio_uml_match);
 static int virtio_uml_suspend(struct platform_device *pdev, pm_message_t state)
 {
 	struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);
-	struct virtqueue *vq;
 
-	virtio_device_for_each_vq((&vu_dev->vdev), vq) {
-		struct virtio_uml_vq_info *info = vq->priv;
+	if (!vu_dev->no_vq_suspend) {
+		struct virtqueue *vq;
 
-		info->suspended = true;
-		vhost_user_set_vring_enable(vu_dev, vq->index, false);
+		virtio_device_for_each_vq((&vu_dev->vdev), vq) {
+			struct virtio_uml_vq_info *info = vq->priv;
+
+			info->suspended = true;
+			vhost_user_set_vring_enable(vu_dev, vq->index, false);
+		}
 	}
 
 	if (!device_may_wakeup(&vu_dev->vdev.dev)) {
@@ -1322,13 +1339,16 @@ static int virtio_uml_suspend(struct platform_device *pdev, pm_message_t state)
 static int virtio_uml_resume(struct platform_device *pdev)
 {
 	struct virtio_uml_device *vu_dev = platform_get_drvdata(pdev);
-	struct virtqueue *vq;
 
-	virtio_device_for_each_vq((&vu_dev->vdev), vq) {
-		struct virtio_uml_vq_info *info = vq->priv;
+	if (!vu_dev->no_vq_suspend) {
+		struct virtqueue *vq;
+
+		virtio_device_for_each_vq((&vu_dev->vdev), vq) {
+			struct virtio_uml_vq_info *info = vq->priv;
 
-		info->suspended = false;
-		vhost_user_set_vring_enable(vu_dev, vq->index, true);
+			info->suspended = false;
+			vhost_user_set_vring_enable(vu_dev, vq->index, true);
+		}
 	}
 
 	vu_dev->suspended = false;
diff --git a/arch/um/include/linux/virtio-uml.h b/arch/um/include/linux/virtio-uml.h
new file mode 100644
index 000000000000..2f652fa90f04
--- /dev/null
+++ b/arch/um/include/linux/virtio-uml.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2021 Intel Corporation
+ * Author: Johannes Berg <johannes@xxxxxxxxxxxxxxxx>
+ */
+
+#ifndef __VIRTIO_UML_H__
+#define __VIRTIO_UML_H__
+
+void virtio_uml_set_no_vq_suspend(struct virtio_device *vdev,
+				  bool no_vq_suspend);
+
+#endif /* __VIRTIO_UML_H__ */
-- 
2.26.2