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Subject[PATCH 7/7] um: virtio/pci: enable suspend/resume
Date
From: Johannes Berg <johannes.berg@intel.com>

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@intel.com>
---
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@sipsolutions.net>
+ */
+
+#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
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