[PATCH 3/3] virtio PCI device

Anthony Liguori
2007-11-08T02:47:38Z

This is a PCI device that implements a transport for virtio. It allows virtio
devices to be used by QEMU based VMMs like KVM or Xen.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig
index 9e33fc4..c81e0f3 100644
--- a/drivers/virtio/Kconfig
+++ b/drivers/virtio/Kconfig
@@ -6,3 +6,20 @@ config VIRTIO
config VIRTIO_RING
bool
depends on VIRTIO
+
+config VIRTIO_PCI
+ tristate "PCI driver for virtio devices (EXPERIMENTAL)"
+ depends on PCI && EXPERIMENTAL
+ select VIRTIO
+ select VIRTIO_RING
+ ---help---
+ This drivers provides support for virtio based paravirtual device
+ drivers over PCI. This requires that your VMM has appropriate PCI
+ virtio backends. Most QEMU based VMMs should support these devices
+ (like KVM or Xen).
+
+ Currently, the ABI is not considered stable so there is no guarantee
+ that this version of the driver will work with your VMM.
+
+ If unsure, say M.
+
diff --git a/drivers/virtio/Makefile b/drivers/virtio/Makefile
index f70e409..cc84999 100644
--- a/drivers/virtio/Makefile
+++ b/drivers/virtio/Makefile
@@ -1,2 +1,3 @@
obj-$(CONFIG_VIRTIO) += virtio.o
obj-$(CONFIG_VIRTIO_RING) += virtio_ring.o
+obj-$(CONFIG_VIRTIO_PCI) += virtio_pci.o
diff --git a/drivers/virtio/virtio_pci.c b/drivers/virtio/virtio_pci.c
new file mode 100644
index 0000000..85ae096
--- /dev/null
+++ b/drivers/virtio/virtio_pci.c
@@ -0,0 +1,469 @@
+#include <linux/module.h>
+#include <linux/list.h>
+#include <linux/pci.h>
+#include <linux/interrupt.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ring.h>
+#include <linux/virtio_pci.h>
+#include <linux/highmem.h>
+#include <linux/spinlock.h>
+
+MODULE_AUTHOR("Anthony Liguori <aliguori@us.ibm.com>");
+MODULE_DESCRIPTION("virtio-pci");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1");
+
+/* Our device structure */
+struct virtio_pci_device
+{
+ /* the virtio device */
+ struct virtio_device vdev;
+ /* the PCI device */
+ struct pci_dev *pci_dev;
+ /* the IO mapping for the PCI config space */
+ void *ioaddr;
+
+ spinlock_t lock;
+ struct list_head virtqueues;
+};
+
+struct virtio_pci_vq_info
+{
+ /* the number of entries in the queue */
+ int num;
+ /* the number of pages the device needs for the ring queue */
+ int n_pages;
+ /* the index of the queue */
+ int queue_index;
+ /* the struct page of the ring queue */
+ struct page *pages;
+ /* the virtual address of the ring queue */
+ void *queue;
+ /* a pointer to the virtqueue */
+ struct virtqueue *vq;
+ /* the node pointer */
+ struct list_head node;
+};
+
+/* We have to enumerate here all virtio PCI devices. */
+static struct pci_device_id virtio_pci_id_table[] = {
+ { 0x5002, 0x2258, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0 }, /* Dummy entry */
+ { 0 },
+};
+
+MODULE_DEVICE_TABLE(pci, virtio_pci_id_table);
+
+/* A PCI device has it's own struct device and so does a virtio device so
+ * we create a place for the virtio devices to show up in sysfs. I think it
+ * would make more sense for virtio to not insist on having it's own device. */
+static struct device virtio_pci_root = {
+ .parent = NULL,
+ .bus_id = "virtio-pci",
+};
+
+/* Unique numbering for devices under the kvm root */
+static unsigned int dev_index;
+
+/* Convert a generic virtio device to our structure */
+static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
+{
+ return container_of(vdev, struct virtio_pci_device, vdev);
+}
+
+/* virtio config->feature() implementation */
+static bool vp_feature(struct virtio_device *vdev, unsigned bit)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+ u32 mask;
+
+ /* Since this function is supposed to have the side effect of
+ * enabling a queried feature, we simulate that by doing a read
+ * from the host feature bitmask and then writing to the guest
+ * feature bitmask */
+ mask = ioread32(vp_dev->ioaddr + VIRTIO_PCI_HOST_FEATURES);
+ if (mask & (1 << bit)) {
+ mask |= (1 << bit);
+ iowrite32(mask, vp_dev->ioaddr + VIRTIO_PCI_GUEST_FEATURES);
+ }
+
+ return !!(mask & (1 << bit));
+}
+
+/* virtio config->get() implementation */
+static void vp_get(struct virtio_device *vdev, unsigned offset,
+ void *buf, unsigned len)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+ void *ioaddr = vp_dev->ioaddr + VIRTIO_PCI_CONFIG + offset;
+
+ /* We translate appropriately sized get requests into more natural
+ * IO operations. These functions also take care of endianness
+ * conversion. */
+ switch (len) {
+ case 1: {
+ u8 val;
+ val = ioread8(ioaddr);
+ memcpy(buf, &val, sizeof(val));
+ break;
+ }
+ case 2: {
+ u16 val;
+ val = ioread16(ioaddr);
+ memcpy(buf, &val, sizeof(val));
+ break;
+ }
+ case 4: {
+ u32 val;
+ val = ioread32(ioaddr);
+ memcpy(buf, &val, sizeof(val));
+ break;
+ }
+ case 8: {
+ u64 val;
+ val = (u64)ioread32(ioaddr) << 32;
+ val |= ioread32(ioaddr + 4);
+ memcpy(buf, &val, sizeof(val));
+ break;
+ }
+
+ /* for strange accesses of an odd size, we do not perform any
+ * endianness conversion. */
+ default:
+ ioread8_rep(ioaddr, buf, len);
+ break;
+ }
+}
+
+/* the config->set() implementation. it's symmetric to the config->get()
+ * implementation */
+static void vp_set(struct virtio_device *vdev, unsigned offset,
+ const void *buf, unsigned len)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+ void *ioaddr = vp_dev->ioaddr + VIRTIO_PCI_CONFIG + offset;
+
+ switch (len) {
+ case 1: {
+ u8 val;
+ memcpy(&val, buf, sizeof(val));
+ iowrite8(val, ioaddr);
+ break;
+ }
+ case 2: {
+ u16 val;
+ memcpy(&val, buf, sizeof(val));
+ iowrite16(val, ioaddr);
+ break;
+ }
+ case 4: {
+ u32 val;
+ memcpy(&val, buf, sizeof(val));
+ iowrite32(val, ioaddr);
+ break;
+ }
+ case 8: {
+ u64 val;
+ memcpy(&val, buf, sizeof(val));
+ iowrite32(val >> 32, ioaddr);
+ iowrite32(val, ioaddr + 4);
+ break;
+ }
+ default:
+ iowrite8_rep(ioaddr, buf, len);
+ break;
+ }
+}
+
+/* config->{get,set}_status() implementations */
+static u8 vp_get_status(struct virtio_device *vdev)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+ return ioread8(vp_dev->ioaddr + VIRTIO_PCI_STATUS);
+}
+
+static void vp_set_status(struct virtio_device *vdev, u8 status)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+ return iowrite8(status, vp_dev->ioaddr + VIRTIO_PCI_STATUS);
+}
+
+/* the notify function used when creating a virt queue */
+static void vp_notify(struct virtqueue *vq)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
+ struct virtio_pci_vq_info *info = vq->priv;
+
+ /* we write the queue's selector into the notification register to
+ * signal the other end */
+ iowrite16(info->queue_index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NOTIFY);
+}
+
+/* A small wrapper to also acknowledge the interrupt when it's handled.
+ * I really need an EIO hook for the vring so I can ack the interrupt once we
+ * know that we'll be handling the IRQ but before we invoke the callback since
+ * the callback may notify the host which results in the host attempting to
+ * raise an interrupt that we would then mask once we acknowledged the
+ * interrupt. */
+static irqreturn_t vp_interrupt(int irq, void *opaque)
+{
+ struct virtio_pci_device *vp_dev = opaque;
+ struct virtio_pci_vq_info *info;
+ irqreturn_t ret = IRQ_NONE;
+ u8 isr;
+
+ /* reading the ISR has the effect of also clearing it so it's very
+ * important to save off the value. */
+ isr = ioread8(vp_dev->ioaddr + VIRTIO_PCI_ISR);
+
+ /* It's definitely not us if the ISR was not high */
+ if (!isr)
+ return IRQ_NONE;
+
+ spin_lock(&vp_dev->lock);
+ list_for_each_entry(info, &vp_dev->virtqueues, node) {
+ if (vring_interrupt(irq, info->vq) == IRQ_HANDLED)
+ ret = IRQ_HANDLED;
+ }
+ spin_unlock(&vp_dev->lock);
+
+ return ret;
+}
+
+/* the config->find_vq() implementation */
+static struct virtqueue *vp_find_vq(struct virtio_device *vdev, unsigned index,
+ bool (*callback)(struct virtqueue *vq))
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vdev);
+ struct virtio_pci_vq_info *info;
+ struct virtqueue *vq;
+ int err;
+ u16 num;
+
+ /* Select the queue we're interested in */
+ iowrite16(index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
+
+ /* Check if queue is either not available or already active. */
+ num = ioread16(vp_dev->ioaddr + VIRTIO_PCI_QUEUE_NUM);
+ if (!num || ioread32(vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN))
+ return ERR_PTR(-ENOENT);
+
+ /* allocate and fill out our structure the represents an active
+ * queue */
+ info = kmalloc(sizeof(struct virtio_pci_vq_info), GFP_KERNEL);
+ if (!info)
+ return ERR_PTR(-ENOMEM);
+
+ info->queue_index = index;
+ info->num = num;
+
+ /* determine the memory needed for the queue and provide the memory
+ * location to the host */
+ info->n_pages = DIV_ROUND_UP(vring_size(num), PAGE_SIZE);
+ info->pages = alloc_pages(GFP_KERNEL | __GFP_ZERO,
+ get_order(info->n_pages));
+ if (info->pages == NULL) {
+ err = -ENOMEM;
+ goto out_info;
+ }
+
+ /* FIXME: is this sufficient for info->n_pages > 1? */
+ info->queue = kmap(info->pages);
+ if (info->queue == NULL) {
+ err = -ENOMEM;
+ goto out_alloc_pages;
+ }
+
+ /* activate the queue */
+ iowrite32(page_to_pfn(info->pages),
+ vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
+
+ /* create the vring */
+ vq = vring_new_virtqueue(info->num, vdev, info->queue,
+ vp_notify, callback);
+ if (!vq) {
+ err = -ENOMEM;
+ goto out_activate_queue;
+ }
+
+ vq->priv = info;
+ info->vq = vq;
+
+ spin_lock(&vp_dev->lock);
+ list_add(&info->node, &vp_dev->virtqueues);
+ spin_unlock(&vp_dev->lock);
+
+ return vq;
+
+out_activate_queue:
+ iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_PFN);
+ kunmap(info->queue);
+out_alloc_pages:
+ __free_pages(info->pages, get_order(info->n_pages));
+out_info:
+ kfree(info);
+ return ERR_PTR(err);
+}
+
+/* the config->del_vq() implementation */
+static void vp_del_vq(struct virtqueue *vq)
+{
+ struct virtio_pci_device *vp_dev = to_vp_device(vq->vdev);
+ struct virtio_pci_vq_info *info = vq->priv;
+
+ spin_lock(&vp_dev->lock);
+ list_del(&info->node);
+ spin_unlock(&vp_dev->lock);
+
+ vring_del_virtqueue(vq);
+
+ /* Select and deactivate the queue */
+ iowrite16(info->queue_index, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
+ iowrite32(0, vp_dev->ioaddr + VIRTIO_PCI_QUEUE_SEL);
+
+ kunmap(info->queue);
+ __free_pages(info->pages, get_order(info->n_pages));
+ kfree(info);
+}
+
+static struct virtio_config_ops virtio_pci_config_ops = {
+ .feature = vp_feature,
+ .get = vp_get,
+ .set = vp_set,
+ .get_status = vp_get_status,
+ .set_status = vp_set_status,
+ .find_vq = vp_find_vq,
+ .del_vq = vp_del_vq,
+};
+
+/* the PCI probing function */
+static int __devinit virtio_pci_probe(struct pci_dev *pci_dev,
+ const struct pci_device_id *id)
+{
+ struct virtio_pci_device *vp_dev;
+ int err;
+
+ /* allocate our structure and fill it out */
+ vp_dev = kzalloc(sizeof(struct virtio_pci_device), GFP_KERNEL);
+ if (vp_dev == NULL)
+ return -ENOMEM;
+
+ vp_dev->pci_dev = pci_dev;
+ vp_dev->vdev.dev.parent = &virtio_pci_root;
+ vp_dev->vdev.index = dev_index++;
+ vp_dev->vdev.config = &virtio_pci_config_ops;
+ INIT_LIST_HEAD(&vp_dev->virtqueues);
+ spin_lock_init(&vp_dev->lock);
+
+ /* enable the device */
+ err = pci_enable_device(pci_dev);
+ if (err)
+ goto out;
+
+ err = pci_request_regions(pci_dev, "virtio-pci");
+ if (err)
+ goto out_enable_device;
+
+ vp_dev->ioaddr = pci_iomap(pci_dev, 0, 0);
+ if (vp_dev->ioaddr == NULL)
+ goto out_req_regions;
+
+ pci_set_drvdata(pci_dev, vp_dev);
+
+ /* we use the subsystem vendor/device id as the virtio vendor/device
+ * id. this allows us to use the same PCI vendor/device id for all
+ * virtio devices and to identify the particular virtio driver by
+ * the subsytem ids */
+ vp_dev->vdev.id.vendor = pci_dev->subsystem_vendor;
+ vp_dev->vdev.id.device = pci_dev->subsystem_device;
+
+ /* register a handler for the queue with the PCI device's interrupt */
+ err = request_irq(vp_dev->pci_dev->irq, vp_interrupt, IRQF_SHARED,
+ pci_name(vp_dev->pci_dev), vp_dev);
+ if (err)
+ goto out_set_drvdata;
+
+ /* finally register the virtio device */
+ err = register_virtio_device(&vp_dev->vdev);
+ if (err)
+ goto out_req_irq;
+
+ return 0;
+
+out_req_irq:
+ free_irq(pci_dev->irq, vp_dev);
+out_set_drvdata:
+ pci_set_drvdata(pci_dev, NULL);
+ pci_iounmap(pci_dev, vp_dev->ioaddr);
+out_req_regions:
+ pci_release_regions(pci_dev);
+out_enable_device:
+ pci_disable_device(pci_dev);
+out:
+ kfree(vp_dev);
+ return err;
+}
+
+static void __devexit virtio_pci_remove(struct pci_dev *pci_dev)
+{
+ struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
+
+ free_irq(pci_dev->irq, vp_dev);
+ pci_set_drvdata(pci_dev, NULL);
+ pci_iounmap(pci_dev, vp_dev->ioaddr);
+ pci_release_regions(pci_dev);
+ pci_disable_device(pci_dev);
+ kfree(vp_dev);
+}
+
+#ifdef CONFIG_PM
+static int virtio_pci_suspend(struct pci_dev *pci_dev, pm_message_t state)
+{
+ pci_save_state(pci_dev);
+ pci_set_power_state(pci_dev, PCI_D3hot);
+ return 0;
+}
+
+static int virtio_pci_resume(struct pci_dev *pci_dev)
+{
+ pci_restore_state(pci_dev);
+ pci_set_power_state(pci_dev, PCI_D0);
+ return 0;
+}
+#endif
+
+static struct pci_driver virtio_pci_driver = {
+ .name = "virtio-pci",
+ .id_table = virtio_pci_id_table,
+ .probe = virtio_pci_probe,
+ .remove = virtio_pci_remove,
+#ifdef CONFIG_PM
+ .suspend = virtio_pci_suspend,
+ .resume = virtio_pci_resume,
+#endif
+};
+
+static int __init virtio_pci_init(void)
+{
+ int err;
+
+ err = device_register(&virtio_pci_root);
+ if (err)
+ return err;
+
+ err = pci_register_driver(&virtio_pci_driver);
+ if (err)
+ device_unregister(&virtio_pci_root);
+
+ return err;
+}
+
+module_init(virtio_pci_init);
+
+static void __exit virtio_pci_exit(void)
+{
+ device_unregister(&virtio_pci_root);
+ pci_unregister_driver(&virtio_pci_driver);
+}
+
+module_exit(virtio_pci_exit);
diff --git a/include/linux/virtio_pci.h b/include/linux/virtio_pci.h
new file mode 100644
index 0000000..b1a1568
--- /dev/null
+++ b/include/linux/virtio_pci.h
@@ -0,0 +1,36 @@
+#ifndef _LINUX_VIRTIO_PCI_H
+#define _LINUX_VIRTIO_PCI_H
+
+#include <linux/virtio_config.h>
+
+/* A 32-bit r/o bitmask of the features supported by the host */
+#define VIRTIO_PCI_HOST_FEATURES 0
+
+/* A 32-bit r/w bitmask of features activated by the guest */
+#define VIRTIO_PCI_GUEST_FEATURES 4
+
+/* A 32-bit r/w PFN for the currently selected queue */
+#define VIRTIO_PCI_QUEUE_PFN 8
+
+/* A 16-bit r/o queue size for the currently selected queue */
+#define VIRTIO_PCI_QUEUE_NUM 12
+
+/* A 16-bit r/w queue selector */
+#define VIRTIO_PCI_QUEUE_SEL 14
+
+/* A 16-bit r/w queue notifier */
+#define VIRTIO_PCI_QUEUE_NOTIFY 16
+
+/* An 8-bit device status register. */
+#define VIRTIO_PCI_STATUS 18
+
+/* An 8-bit r/o interrupt status register. Reading the value will return the
+ * current contents of the ISR and will also clear it. This is effectively
+ * a read-and-acknowledge. */
+#define VIRTIO_PCI_ISR 19
+
+/* The remaining space is defined by each driver as the per-driver
+ * configuration space */
+#define VIRTIO_PCI_CONFIG 20
+
+#endif