1 files changed, 116 insertions, 579 deletions
diff --git a/arch/um/drivers/virt-pci.c b/arch/um/drivers/virt-pci.c
index 744e7f31e8ef..b83b5a765d4e 100644
--- a/arch/um/drivers/virt-pci.c
+++ b/arch/um/drivers/virt-pci.c
@@ -5,45 +5,19 @@
  */
 #include <linux/module.h>
 #include <linux/pci.h>
-#include <linux/virtio.h>
-#include <linux/virtio_config.h>
 #include <linux/logic_iomem.h>
 #include <linux/of_platform.h>
 #include <linux/irqdomain.h>
-#include <linux/virtio_pcidev.h>
-#include <linux/virtio-uml.h>
-#include <linux/delay.h>
 #include <linux/msi.h>
 #include <linux/unaligned.h>
 #include <irq_kern.h>
 
+#include "virt-pci.h"
+
 #define MAX_DEVICES 8
 #define MAX_MSI_VECTORS 32
 #define CFG_SPACE_SIZE 4096
 
-/* for MSI-X we have a 32-bit payload */
-#define MAX_IRQ_MSG_SIZE (sizeof(struct virtio_pcidev_msg) + sizeof(u32))
-#define NUM_IRQ_MSGS	10
-
-#define HANDLE_NO_FREE(ptr) ((void *)((unsigned long)(ptr) | 1))
-#define HANDLE_IS_NO_FREE(ptr) ((unsigned long)(ptr) & 1)
-
-struct um_pci_device {
-	struct virtio_device *vdev;
-
-	/* for now just standard BARs */
-	u8 resptr[PCI_STD_NUM_BARS];
-
-	struct virtqueue *cmd_vq, *irq_vq;
-
-#define UM_PCI_STAT_WAITING	0
-	unsigned long status;
-
-	int irq;
-
-	bool platform;
-};
-
 struct um_pci_device_reg {
 	struct um_pci_device *dev;
 	void __iomem *iomem;
@@ -58,150 +32,15 @@ static struct irq_domain *um_pci_inner_domain;
 static struct irq_domain *um_pci_msi_domain;
 static unsigned long um_pci_msi_used[BITS_TO_LONGS(MAX_MSI_VECTORS)];
 
-static unsigned int um_pci_max_delay_us = 40000;
-module_param_named(max_delay_us, um_pci_max_delay_us, uint, 0644);
-
-struct um_pci_message_buffer {
-	struct virtio_pcidev_msg hdr;
-	u8 data[8];
-};
-
-static struct um_pci_message_buffer __percpu *um_pci_msg_bufs;
-
-static int um_pci_send_cmd(struct um_pci_device *dev,
-			   struct virtio_pcidev_msg *cmd,
-			   unsigned int cmd_size,
-			   const void *extra, unsigned int extra_size,
-			   void *out, unsigned int out_size)
-{
-	struct scatterlist out_sg, extra_sg, in_sg;
-	struct scatterlist *sgs_list[] = {
-		[0] = &out_sg,
-		[1] = extra ? &extra_sg : &in_sg,
-		[2] = extra ? &in_sg : NULL,
-	};
-	struct um_pci_message_buffer *buf;
-	int delay_count = 0;
-	int ret, len;
-	bool posted;
-
-	if (WARN_ON(cmd_size < sizeof(*cmd) || cmd_size > sizeof(*buf)))
-		return -EINVAL;
-
-	switch (cmd->op) {
-	case VIRTIO_PCIDEV_OP_CFG_WRITE:
-	case VIRTIO_PCIDEV_OP_MMIO_WRITE:
-	case VIRTIO_PCIDEV_OP_MMIO_MEMSET:
-		/* in PCI, writes are posted, so don't wait */
-		posted = !out;
-		WARN_ON(!posted);
-		break;
-	default:
-		posted = false;
-		break;
-	}
-
-	buf = get_cpu_var(um_pci_msg_bufs);
-	if (buf)
-		memcpy(buf, cmd, cmd_size);
-
-	if (posted) {
-		u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC);
-
-		if (ncmd) {
-			memcpy(ncmd, cmd, cmd_size);
-			if (extra)
-				memcpy(ncmd + cmd_size, extra, extra_size);
-			cmd = (void *)ncmd;
-			cmd_size += extra_size;
-			extra = NULL;
-			extra_size = 0;
-		} else {
-			/* try without allocating memory */
-			posted = false;
-			cmd = (void *)buf;
-		}
-	} else {
-		cmd = (void *)buf;
-	}
-
-	sg_init_one(&out_sg, cmd, cmd_size);
-	if (extra)
-		sg_init_one(&extra_sg, extra, extra_size);
-	if (out)
-		sg_init_one(&in_sg, out, out_size);
-
-	/* add to internal virtio queue */
-	ret = virtqueue_add_sgs(dev->cmd_vq, sgs_list,
-				extra ? 2 : 1,
-				out ? 1 : 0,
-				posted ? cmd : HANDLE_NO_FREE(cmd),
-				GFP_ATOMIC);
-	if (ret) {
-		if (posted)
-			kfree(cmd);
-		goto out;
-	}
-
-	if (posted) {
-		virtqueue_kick(dev->cmd_vq);
-		ret = 0;
-		goto out;
-	}
-
-	/* kick and poll for getting a response on the queue */
-	set_bit(UM_PCI_STAT_WAITING, &dev->status);
-	virtqueue_kick(dev->cmd_vq);
-
-	while (1) {
-		void *completed = virtqueue_get_buf(dev->cmd_vq, &len);
-
-		if (completed == HANDLE_NO_FREE(cmd))
-			break;
-
-		if (completed && !HANDLE_IS_NO_FREE(completed))
-			kfree(completed);
-
-		if (WARN_ONCE(virtqueue_is_broken(dev->cmd_vq) ||
-			      ++delay_count > um_pci_max_delay_us,
-			      "um virt-pci delay: %d", delay_count)) {
-			ret = -EIO;
-			break;
-		}
-		udelay(1);
-	}
-	clear_bit(UM_PCI_STAT_WAITING, &dev->status);
-
-out:
-	put_cpu_var(um_pci_msg_bufs);
-	return ret;
-}
-
 static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
 					  int size)
 {
 	struct um_pci_device_reg *reg = priv;
 	struct um_pci_device *dev = reg->dev;
-	struct virtio_pcidev_msg hdr = {
-		.op = VIRTIO_PCIDEV_OP_CFG_READ,
-		.size = size,
-		.addr = offset,
-	};
-	/* buf->data is maximum size - we may only use parts of it */
-	struct um_pci_message_buffer *buf;
-	u8 *data;
-	unsigned long ret = ULONG_MAX;
-	size_t bytes = sizeof(buf->data);
 
 	if (!dev)
 		return ULONG_MAX;
 
-	buf = get_cpu_var(um_pci_msg_bufs);
-	data = buf->data;
-
-	if (buf)
-		memset(data, 0xff, bytes);
-
 	switch (size) {
 	case 1:
 	case 2:
@@ -212,34 +51,10 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
 		break;
 	default:
 		WARN(1, "invalid config space read size %d\n", size);
-		goto out;
-	}
-
-	if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, bytes))
-		goto out;
-
-	switch (size) {
-	case 1:
-		ret = data[0];
-		break;
-	case 2:
-		ret = le16_to_cpup((void *)data);
-		break;
-	case 4:
-		ret = le32_to_cpup((void *)data);
-		break;
-#ifdef CONFIG_64BIT
-	case 8:
-		ret = le64_to_cpup((void *)data);
-		break;
-#endif
-	default:
-		break;
+		return ULONG_MAX;
 	}
 
-out:
-	put_cpu_var(um_pci_msg_bufs);
-	return ret;
+	return dev->ops->cfgspace_read(dev, offset, size);
 }
 
 static void um_pci_cfgspace_write(void *priv, unsigned int offset, int size,
@@ -247,42 +62,24 @@ static void um_pci_cfgspace_write(void *priv, unsigned int offset, int size,
 {
 	struct um_pci_device_reg *reg = priv;
 	struct um_pci_device *dev = reg->dev;
-	struct {
-		struct virtio_pcidev_msg hdr;
-		/* maximum size - we may only use parts of it */
-		u8 data[8];
-	} msg = {
-		.hdr = {
-			.op = VIRTIO_PCIDEV_OP_CFG_WRITE,
-			.size = size,
-			.addr = offset,
-		},
-	};
 
 	if (!dev)
 		return;
 
 	switch (size) {
 	case 1:
-		msg.data[0] = (u8)val;
-		break;
 	case 2:
-		put_unaligned_le16(val, (void *)msg.data);
-		break;
 	case 4:
-		put_unaligned_le32(val, (void *)msg.data);
-		break;
 #ifdef CONFIG_64BIT
 	case 8:
-		put_unaligned_le64(val, (void *)msg.data);
-		break;
 #endif
+		break;
 	default:
 		WARN(1, "invalid config space write size %d\n", size);
 		return;
 	}
 
-	WARN_ON(um_pci_send_cmd(dev, &msg.hdr, sizeof(msg), NULL, 0, NULL, 0));
+	dev->ops->cfgspace_write(dev, offset, size, val);
 }
 
 static const struct logic_iomem_ops um_pci_device_cfgspace_ops = {
@@ -290,35 +87,14 @@ static const struct logic_iomem_ops um_pci_device_cfgspace_ops = {
 	.write = um_pci_cfgspace_write,
 };
 
-static void um_pci_bar_copy_from(void *priv, void *buffer,
-				 unsigned int offset, int size)
+static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
+				     int size)
 {
 	u8 *resptr = priv;
 	struct um_pci_device *dev = container_of(resptr - *resptr,
 						 struct um_pci_device,
 						 resptr[0]);
-	struct virtio_pcidev_msg hdr = {
-		.op = VIRTIO_PCIDEV_OP_MMIO_READ,
-		.bar = *resptr,
-		.size = size,
-		.addr = offset,
-	};
-
-	memset(buffer, 0xff, size);
-
-	um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, buffer, size);
-}
-
-static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
-				     int size)
-{
-	/* buf->data is maximum size - we may only use parts of it */
-	struct um_pci_message_buffer *buf;
-	u8 *data;
-	unsigned long ret = ULONG_MAX;
-
-	buf = get_cpu_var(um_pci_msg_bufs);
-	data = buf->data;
+	u8 bar = *resptr;
 
 	switch (size) {
 	case 1:
@@ -329,80 +105,60 @@ static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
 #endif
 		break;
 	default:
-		WARN(1, "invalid config space read size %d\n", size);
-		goto out;
+		WARN(1, "invalid bar read size %d\n", size);
+		return ULONG_MAX;
 	}
 
-	um_pci_bar_copy_from(priv, data, offset, size);
+	return dev->ops->bar_read(dev, bar, offset, size);
+}
+
+static void um_pci_bar_write(void *priv, unsigned int offset, int size,
+			     unsigned long val)
+{
+	u8 *resptr = priv;
+	struct um_pci_device *dev = container_of(resptr - *resptr,
+						 struct um_pci_device,
+						 resptr[0]);
+	u8 bar = *resptr;
 
 	switch (size) {
 	case 1:
-		ret = data[0];
-		break;
 	case 2:
-		ret = le16_to_cpup((void *)data);
-		break;
 	case 4:
-		ret = le32_to_cpup((void *)data);
-		break;
 #ifdef CONFIG_64BIT
 	case 8:
-		ret = le64_to_cpup((void *)data);
-		break;
 #endif
-	default:
 		break;
+	default:
+		WARN(1, "invalid bar write size %d\n", size);
+		return;
 	}
 
-out:
-	put_cpu_var(um_pci_msg_bufs);
-	return ret;
+	dev->ops->bar_write(dev, bar, offset, size, val);
 }
 
-static void um_pci_bar_copy_to(void *priv, unsigned int offset,
-			       const void *buffer, int size)
+static void um_pci_bar_copy_from(void *priv, void *buffer,
+				 unsigned int offset, int size)
 {
 	u8 *resptr = priv;
 	struct um_pci_device *dev = container_of(resptr - *resptr,
 						 struct um_pci_device,
 						 resptr[0]);
-	struct virtio_pcidev_msg hdr = {
-		.op = VIRTIO_PCIDEV_OP_MMIO_WRITE,
-		.bar = *resptr,
-		.size = size,
-		.addr = offset,
-	};
+	u8 bar = *resptr;
 
-	um_pci_send_cmd(dev, &hdr, sizeof(hdr), buffer, size, NULL, 0);
+	dev->ops->bar_copy_from(dev, bar, buffer, offset, size);
 }
 
-static void um_pci_bar_write(void *priv, unsigned int offset, int size,
-			     unsigned long val)
+static void um_pci_bar_copy_to(void *priv, unsigned int offset,
+			       const void *buffer, int size)
 {
-	/* maximum size - we may only use parts of it */
-	u8 data[8];
-
-	switch (size) {
-	case 1:
-		data[0] = (u8)val;
-		break;
-	case 2:
-		put_unaligned_le16(val, (void *)data);
-		break;
-	case 4:
-		put_unaligned_le32(val, (void *)data);
-		break;
-#ifdef CONFIG_64BIT
-	case 8:
-		put_unaligned_le64(val, (void *)data);
-		break;
-#endif
-	default:
-		WARN(1, "invalid config space write size %d\n", size);
-		return;
-	}
+	u8 *resptr = priv;
+	struct um_pci_device *dev = container_of(resptr - *resptr,
+						 struct um_pci_device,
+						 resptr[0]);
+	u8 bar = *resptr;
 
-	um_pci_bar_copy_to(priv, offset, data, size);
+	dev->ops->bar_copy_to(dev, bar, offset, buffer, size);
 }
 
 static void um_pci_bar_set(void *priv, unsigned int offset, u8 value, int size)
@@ -411,20 +167,9 @@ static void um_pci_bar_set(void *priv, unsigned int offset, u8 value, int size)
 	struct um_pci_device *dev = container_of(resptr - *resptr,
 						 struct um_pci_device,
 						 resptr[0]);
-	struct {
-		struct virtio_pcidev_msg hdr;
-		u8 data;
-	} msg = {
-		.hdr = {
-			.op = VIRTIO_PCIDEV_OP_CFG_WRITE,
-			.bar = *resptr,
-			.size = size,
-			.addr = offset,
-		},
-		.data = value,
-	};
+	u8 bar = *resptr;
 
-	um_pci_send_cmd(dev, &msg.hdr, sizeof(msg), NULL, 0, NULL, 0);
+	dev->ops->bar_set(dev, bar, offset, value, size);
 }
 
 static const struct logic_iomem_ops um_pci_device_bar_ops = {
@@ -471,79 +216,6 @@ static void um_pci_rescan(void)
 	pci_unlock_rescan_remove();
 }
 
-static void um_pci_irq_vq_addbuf(struct virtqueue *vq, void *buf, bool kick)
-{
-	struct scatterlist sg[1];
-
-	sg_init_one(sg, buf, MAX_IRQ_MSG_SIZE);
-	if (virtqueue_add_inbuf(vq, sg, 1, buf, GFP_ATOMIC))
-		kfree(buf);
-	else if (kick)
-		virtqueue_kick(vq);
-}
-
-static void um_pci_handle_irq_message(struct virtqueue *vq,
-				      struct virtio_pcidev_msg *msg)
-{
-	struct virtio_device *vdev = vq->vdev;
-	struct um_pci_device *dev = vdev->priv;
-
-	if (!dev->irq)
-		return;
-
-	/* we should properly chain interrupts, but on ARCH=um we don't care */
-
-	switch (msg->op) {
-	case VIRTIO_PCIDEV_OP_INT:
-		generic_handle_irq(dev->irq);
-		break;
-	case VIRTIO_PCIDEV_OP_MSI:
-		/* our MSI message is just the interrupt number */
-		if (msg->size == sizeof(u32))
-			generic_handle_irq(le32_to_cpup((void *)msg->data));
-		else
-			generic_handle_irq(le16_to_cpup((void *)msg->data));
-		break;
-	case VIRTIO_PCIDEV_OP_PME:
-		/* nothing to do - we already woke up due to the message */
-		break;
-	default:
-		dev_err(&vdev->dev, "unexpected virt-pci message %d\n", msg->op);
-		break;
-	}
-}
-
-static void um_pci_cmd_vq_cb(struct virtqueue *vq)
-{
-	struct virtio_device *vdev = vq->vdev;
-	struct um_pci_device *dev = vdev->priv;
-	void *cmd;
-	int len;
-
-	if (test_bit(UM_PCI_STAT_WAITING, &dev->status))
-		return;
-
-	while ((cmd = virtqueue_get_buf(vq, &len))) {
-		if (WARN_ON(HANDLE_IS_NO_FREE(cmd)))
-			continue;
-		kfree(cmd);
-	}
-}
-
-static void um_pci_irq_vq_cb(struct virtqueue *vq)
-{
-	struct virtio_pcidev_msg *msg;
-	int len;
-
-	while ((msg = virtqueue_get_buf(vq, &len))) {
-		if (len >= sizeof(*msg))
-			um_pci_handle_irq_message(vq, msg);
-
-		/* recycle the message buffer */
-		um_pci_irq_vq_addbuf(vq, msg, true);
-	}
-}
-
 #ifdef CONFIG_OF
 /* Copied from arch/x86/kernel/devicetree.c */
 struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus)
@@ -565,200 +237,6 @@ struct device_node *pcibios_get_phb_of_node(struct pci_bus *bus)
 }
 #endif
 
-static int um_pci_init_vqs(struct um_pci_device *dev)
-{
-	struct virtqueue_info vqs_info[] = {
-		{ "cmd", um_pci_cmd_vq_cb },
-		{ "irq", um_pci_irq_vq_cb },
-	};
-	struct virtqueue *vqs[2];
-	int err, i;
-
-	err = virtio_find_vqs(dev->vdev, 2, vqs, vqs_info, NULL);
-	if (err)
-		return err;
-
-	dev->cmd_vq = vqs[0];
-	dev->irq_vq = vqs[1];
-
-	virtio_device_ready(dev->vdev);
-
-	for (i = 0; i < NUM_IRQ_MSGS; i++) {
-		void *msg = kzalloc(MAX_IRQ_MSG_SIZE, GFP_KERNEL);
-
-		if (msg)
-			um_pci_irq_vq_addbuf(dev->irq_vq, msg, false);
-	}
-
-	virtqueue_kick(dev->irq_vq);
-
-	return 0;
-}
-
-static void __um_pci_virtio_platform_remove(struct virtio_device *vdev,
-					    struct um_pci_device *dev)
-{
-	virtio_reset_device(vdev);
-	vdev->config->del_vqs(vdev);
-
-	mutex_lock(&um_pci_mtx);
-	um_pci_platform_device = NULL;
-	mutex_unlock(&um_pci_mtx);
-
-	kfree(dev);
-}
-
-static int um_pci_virtio_platform_probe(struct virtio_device *vdev,
-					struct um_pci_device *dev)
-{
-	int ret;
-
-	dev->platform = true;
-
-	mutex_lock(&um_pci_mtx);
-
-	if (um_pci_platform_device) {
-		mutex_unlock(&um_pci_mtx);
-		ret = -EBUSY;
-		goto out_free;
-	}
-
-	ret = um_pci_init_vqs(dev);
-	if (ret) {
-		mutex_unlock(&um_pci_mtx);
-		goto out_free;
-	}
-
-	um_pci_platform_device = dev;
-
-	mutex_unlock(&um_pci_mtx);
-
-	ret = of_platform_default_populate(vdev->dev.of_node, NULL, &vdev->dev);
-	if (ret)
-		__um_pci_virtio_platform_remove(vdev, dev);
-
-	return ret;
-
-out_free:
-	kfree(dev);
-	return ret;
-}
-
-static int um_pci_virtio_probe(struct virtio_device *vdev)
-{
-	struct um_pci_device *dev;
-	int i, free = -1;
-	int err = -ENOSPC;
-
-	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
-	if (!dev)
-		return -ENOMEM;
-
-	dev->vdev = vdev;
-	vdev->priv = dev;
-
-	if (of_device_is_compatible(vdev->dev.of_node, "simple-bus"))
-		return um_pci_virtio_platform_probe(vdev, dev);
-
-	mutex_lock(&um_pci_mtx);
-	for (i = 0; i < MAX_DEVICES; i++) {
-		if (um_pci_devices[i].dev)
-			continue;
-		free = i;
-		break;
-	}
-
-	if (free < 0)
-		goto error;
-
-	err = um_pci_init_vqs(dev);
-	if (err)
-		goto error;
-
-	dev->irq = irq_alloc_desc(numa_node_id());
-	if (dev->irq < 0) {
-		err = dev->irq;
-		goto err_reset;
-	}
-	um_pci_devices[free].dev = dev;
-	vdev->priv = dev;
-
-	mutex_unlock(&um_pci_mtx);
-
-	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;
-err_reset:
-	virtio_reset_device(vdev);
-	vdev->config->del_vqs(vdev);
-error:
-	mutex_unlock(&um_pci_mtx);
-	kfree(dev);
-	return err;
-}
-
-static void um_pci_virtio_remove(struct virtio_device *vdev)
-{
-	struct um_pci_device *dev = vdev->priv;
-	int i;
-
-	if (dev->platform) {
-		of_platform_depopulate(&vdev->dev);
-		__um_pci_virtio_platform_remove(vdev, dev);
-		return;
-	}
-
-	device_set_wakeup_enable(&vdev->dev, false);
-
-	mutex_lock(&um_pci_mtx);
-	for (i = 0; i < MAX_DEVICES; i++) {
-		if (um_pci_devices[i].dev != dev)
-			continue;
-
-		um_pci_devices[i].dev = NULL;
-		irq_free_desc(dev->irq);
-
-		break;
-	}
-	mutex_unlock(&um_pci_mtx);
-
-	if (i < MAX_DEVICES) {
-		struct pci_dev *pci_dev;
-
-		pci_dev = pci_get_slot(bridge->bus, i);
-		if (pci_dev)
-			pci_stop_and_remove_bus_device_locked(pci_dev);
-	}
-
-	/* Stop all virtqueues */
-	virtio_reset_device(vdev);
-	dev->cmd_vq = NULL;
-	dev->irq_vq = NULL;
-	vdev->config->del_vqs(vdev);
-
-	kfree(dev);
-}
-
-static struct virtio_device_id id_table[] = {
-	{ CONFIG_UML_PCI_OVER_VIRTIO_DEVICE_ID, VIRTIO_DEV_ANY_ID },
-	{ 0 },
-};
-MODULE_DEVICE_TABLE(virtio, id_table);
-
-static struct virtio_driver um_pci_virtio_driver = {
-	.driver.name = "virtio-pci",
-	.id_table = id_table,
-	.probe = um_pci_virtio_probe,
-	.remove = um_pci_virtio_remove,
-};
-
 static struct resource virt_cfgspace_resource = {
 	.name = "PCI config space",
 	.start = 0xf0000000 - MAX_DEVICES * CFG_SPACE_SIZE,
@@ -877,7 +355,7 @@ static void um_pci_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 }
 
 static struct irq_chip um_pci_msi_bottom_irq_chip = {
-	.name = "UM virtio MSI",
+	.name = "UM virtual MSI",
 	.irq_compose_msi_msg = um_pci_compose_msi_msg,
 };
 
@@ -927,7 +405,7 @@ static const struct irq_domain_ops um_pci_inner_domain_ops = {
 };
 
 static struct irq_chip um_pci_msi_irq_chip = {
-	.name = "UM virtio PCIe MSI",
+	.name = "UM virtual PCIe MSI",
 	.irq_mask = pci_msi_mask_irq,
 	.irq_unmask = pci_msi_unmask_irq,
 };
@@ -986,6 +464,78 @@ static struct resource virt_platform_resource = {
 	.flags = IORESOURCE_MEM,
 };
 
+int um_pci_device_register(struct um_pci_device *dev)
+{
+	int i, free = -1;
+	int err = 0;
+
+	mutex_lock(&um_pci_mtx);
+	for (i = 0; i < MAX_DEVICES; i++) {
+		if (um_pci_devices[i].dev)
+			continue;
+		free = i;
+		break;
+	}
+
+	if (free < 0) {
+		err = -ENOSPC;
+		goto out;
+	}
+
+	dev->irq = irq_alloc_desc(numa_node_id());
+	if (dev->irq < 0) {
+		err = dev->irq;
+		goto out;
+	}
+
+	um_pci_devices[free].dev = dev;
+
+out:
+	mutex_unlock(&um_pci_mtx);
+	if (!err)
+		um_pci_rescan();
+	return err;
+}
+
+void um_pci_device_unregister(struct um_pci_device *dev)
+{
+	int i;
+
+	mutex_lock(&um_pci_mtx);
+	for (i = 0; i < MAX_DEVICES; i++) {
+		if (um_pci_devices[i].dev != dev)
+			continue;
+		um_pci_devices[i].dev = NULL;
+		irq_free_desc(dev->irq);
+		break;
+	}
+	mutex_unlock(&um_pci_mtx);
+
+	if (i < MAX_DEVICES) {
+		struct pci_dev *pci_dev;
+
+		pci_dev = pci_get_slot(bridge->bus, i);
+		if (pci_dev)
+			pci_stop_and_remove_bus_device_locked(pci_dev);
+	}
+}
+
+int um_pci_platform_device_register(struct um_pci_device *dev)
+{
+	guard(mutex)(&um_pci_mtx);
+	if (um_pci_platform_device)
+		return -EBUSY;
+	um_pci_platform_device = dev;
+	return 0;
+}
+
+void um_pci_platform_device_unregister(struct um_pci_device *dev)
+{
+	guard(mutex)(&um_pci_mtx);
+	if (um_pci_platform_device == dev)
+		um_pci_platform_device = NULL;
+}
+
 static int __init um_pci_init(void)
 {
 	struct irq_domain_info inner_domain_info = {
@@ -1002,14 +552,6 @@ static int __init um_pci_init(void)
 	WARN_ON(logic_iomem_add_region(&virt_platform_resource,
 				       &um_pci_platform_ops));
 
-	if (WARN(CONFIG_UML_PCI_OVER_VIRTIO_DEVICE_ID < 0,
-		 "No virtio device ID configured for PCI - no PCI support\n"))
-		return 0;
-
-	um_pci_msg_bufs = alloc_percpu(struct um_pci_message_buffer);
-	if (!um_pci_msg_bufs)
-		return -ENOMEM;
-
 	bridge = pci_alloc_host_bridge(0);
 	if (!bridge) {
 		err = -ENOMEM;
@@ -1057,10 +599,8 @@ static int __init um_pci_init(void)
 	if (err)
 		goto free;
 
-	err = register_virtio_driver(&um_pci_virtio_driver);
-	if (err)
-		goto free;
 	return 0;
+
 free:
 	if (!IS_ERR_OR_NULL(um_pci_inner_domain))
 		irq_domain_remove(um_pci_inner_domain);
@@ -1070,18 +610,15 @@ free:
 		pci_free_resource_list(&bridge->windows);
 		pci_free_host_bridge(bridge);
 	}
-	free_percpu(um_pci_msg_bufs);
 	return err;
 }
-module_init(um_pci_init);
+device_initcall(um_pci_init);
 
 static void __exit um_pci_exit(void)
 {
-	unregister_virtio_driver(&um_pci_virtio_driver);
 	irq_domain_remove(um_pci_msi_domain);
 	irq_domain_remove(um_pci_inner_domain);
 	pci_free_resource_list(&bridge->windows);
 	pci_free_host_bridge(bridge);
-	free_percpu(um_pci_msg_bufs);
 }
 module_exit(um_pci_exit);