[PATCH 1/6] Basic virtio infrastructure for QEMU (v2)

Anthony Liguori
2007-11-11T03:20:35Z

This implements the basic virtio and virtio_ring infrastructure for QEMU. It's
designed at the moment with intimate knowledge of the virtio_pci device. In
the future, we may want to abstract that a little further so that the virtio
backend device doesn't have any knowledge of the virtio transport.

Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>

diff --git a/qemu/Makefile.target b/qemu/Makefile.target
index 65f449e..c7686b2 100644
--- a/qemu/Makefile.target
+++ b/qemu/Makefile.target
@@ -448,6 +448,9 @@ VL_OBJS += rtl8139.o
# PCI Hypercall
VL_OBJS+= hypercall.o

+# virtio devices
+VL_OBJS += virtio.o
+
ifeq ($(TARGET_BASE_ARCH), i386)
# Hardware support
VL_OBJS+= ide.o pckbd.o ps2.o vga.o $(SOUND_HW) dma.o $(AUDIODRV)
diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
new file mode 100644
index 0000000..e30ffb1
--- /dev/null
+++ b/qemu/hw/virtio.c
@@ -0,0 +1,336 @@
+/*
+ * Virtio Support
+ *
+ * Copyright IBM, Corp. 2007
+ *
+ * Authors:
+ * Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "vl.h"
+#include "virtio.h"
+#include <err.h>
+
+/* from Linux's linux/virtio_pci.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
+
+/* A 32-bit r/o configuration size. This is the amount of memory required
+ * to be allocated for VIRTIO_PCI_CONFIG_PFN. */
+#define VIRTIO_PCI_CONFIG_LEN 20
+
+/* A 32-bit r/w PFN for the shared configuration information. The PA written
+ * by the host must point to at least VIRTIO_PCI_CONFIG_LEN bytes */
+#define VIRTIO_PCI_CONFIG_PFN 24
+
+/* virt queue functions */
+
+#define wmb() asm volatile("sfence" ::: "memory")
+
+static void virtqueue_init(VirtQueue *vq, void *p)
+{
+ vq->vring.desc = p;
+ vq->vring.avail = p + vq->vring.num * sizeof(VRingDesc);
+ vq->vring.used = p + (vq->vring.num + 1) *
+ (sizeof(VRingDesc) + sizeof(uint16_t));
+}
+
+static unsigned virtqueue_next_desc(VirtQueue *vq, unsigned int i)
+{
+ unsigned int next;
+
+ /* If this descriptor says it doesn't chain, we're done. */
+ if (!(vq->vring.desc[i].flags & VRING_DESC_F_NEXT))
+ return vq->vring.num;
+
+ /* Check they're not leading us off end of descriptors. */
+ next = vq->vring.desc[i].next;
+ /* Make sure compiler knows to grab that: we don't want it changing! */
+ wmb();
+
+ if (next >= vq->vring.num)
+ errx(1, "Desc next is %u", next);
+
+ return next;
+}
+
+void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
+ unsigned int len)
+{
+ VRingUsedElem *used;
+
+ /* Get a pointer to the next entry in the used ring. */
+ used = &vq->vring.used->ring[vq->vring.used->idx % vq->vring.num];
+ used->id = elem->index;
+ used->len = len;
+ /* Make sure buffer is written before we update index. */
+ wmb();
+ vq->vring.used->idx++;
+}
+
+int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem)
+{
+ unsigned int i, head;
+ unsigned int position;
+
+ /* Check it isn't doing very strange things with descriptor numbers. */
+ if ((uint16_t)(vq->vring.avail->idx - vq->last_avail_idx) > vq->vring.num)
+ errx(1, "Guest moved used index from %u to %u",
+ vq->last_avail_idx, vq->vring.avail->idx);
+
+ /* If there's nothing new since last we looked, return invalid. */
+ if (vq->vring.avail->idx == vq->last_avail_idx)
+ return 0;
+
+ /* Grab the next descriptor number they're advertising, and increment
+ * the index we've seen. */
+ head = vq->vring.avail->ring[vq->last_avail_idx++ % vq->vring.num];
+
+ /* If their number is silly, that's a fatal mistake. */
+ if (head >= vq->vring.num)
+ errx(1, "Guest says index %u is available", head);
+
+ /* When we start there are none of either input nor output. */
+ position = elem->out_num = elem->in_num = 0;
+
+ i = head;
+ do {
+ struct iovec *sg;
+
+ if ((vq->vring.desc[i].addr + vq->vring.desc[i].len) > ram_size)
+ errx(1, "Guest sent invalid pointer");
+
+ if (vq->vring.desc[i].flags & VRING_DESC_F_WRITE)
+ sg = &elem->in_sg[elem->in_num++];
+ else
+ sg = &elem->out_sg[elem->out_num++];
+
+ /* Grab the first descriptor, and check it's OK. */
+ sg->iov_len = vq->vring.desc[i].len;
+ sg->iov_base = phys_ram_base + vq->vring.desc[i].addr;
+
+ /* If we've got too many, that implies a descriptor loop. */
+ if ((elem->in_num + elem->out_num) > vq->vring.num)
+ errx(1, "Looped descriptor");
+ } while ((i = virtqueue_next_desc(vq, i)) != vq->vring.num);
+
+ elem->index = head;
+
+ return elem->in_num + elem->out_num;
+}
+
+/* virtio device */
+
+static VirtIODevice *to_virtio_device(PCIDevice *pci_dev)
+{
+ return (VirtIODevice *)pci_dev;
+}
+
+static void virtio_update_irq(VirtIODevice *vdev)
+{
+ qemu_set_irq(vdev->pci_dev.irq[0], vdev->isr & 1);
+}
+
+static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val)
+{
+ VirtIODevice *vdev = to_virtio_device(opaque);
+ ram_addr_t pa;
+
+ addr -= vdev->addr;
+
+ switch (addr) {
+ case VIRTIO_PCI_GUEST_FEATURES:
+ if (vdev->set_features)
+ vdev->set_features(vdev, val);
+ vdev->features = val;
+ break;
+ case VIRTIO_PCI_QUEUE_PFN:
+ pa = (ram_addr_t)val << TARGET_PAGE_BITS;
+ vdev->vq[vdev->queue_sel].pfn = val;
+ if (pa == 0) {
+ vdev->vq[vdev->queue_sel].vring.desc = NULL;
+ vdev->vq[vdev->queue_sel].vring.avail = NULL;
+ vdev->vq[vdev->queue_sel].vring.used = NULL;
+ } else if (pa < (ram_size - TARGET_PAGE_SIZE)) {
+ virtqueue_init(&vdev->vq[vdev->queue_sel], phys_ram_base + pa);
+ /* FIXME if pa == 0, deal with device tear down */
+ }
+ break;
+ case VIRTIO_PCI_QUEUE_SEL:
+ if (val < VIRTIO_PCI_QUEUE_MAX)
+ vdev->queue_sel = val;
+ break;
+ case VIRTIO_PCI_QUEUE_NOTIFY:
+ if (val < VIRTIO_PCI_QUEUE_MAX && vdev->vq[val].vring.desc)
+ vdev->vq[val].handle_output(vdev, &vdev->vq[val]);
+ break;
+ case VIRTIO_PCI_STATUS:
+ vdev->status = val & 0xFF;
+ break;
+ case VIRTIO_PCI_CONFIG_PFN:
+ pa = (ram_addr_t)val << TARGET_PAGE_BITS;
+ if (pa && pa < (ram_size - vdev->config_len) && vdev->update_config)
+ vdev->update_config(vdev, phys_ram_base + pa);
+ vdev->config_pfn = val;
+ break;
+ }
+}
+
+static uint32_t virtio_ioport_read(void *opaque, uint32_t addr)
+{
+ VirtIODevice *vdev = to_virtio_device(opaque);
+ uint32_t ret = 0xFFFFFFFF;
+
+ addr -= vdev->addr;
+
+ switch (addr) {
+ case VIRTIO_PCI_HOST_FEATURES:
+ ret = vdev->get_features(vdev);
+ break;
+ case VIRTIO_PCI_GUEST_FEATURES:
+ ret = vdev->features;
+ break;
+ case VIRTIO_PCI_QUEUE_PFN:
+ ret = vdev->vq[vdev->queue_sel].pfn;
+ break;
+ case VIRTIO_PCI_QUEUE_NUM:
+ ret = vdev->vq[vdev->queue_sel].vring.num;
+ break;
+ case VIRTIO_PCI_QUEUE_SEL:
+ ret = vdev->queue_sel;
+ break;
+ case VIRTIO_PCI_STATUS:
+ ret = vdev->status;
+ break;
+ case VIRTIO_PCI_ISR:
+ /* reading from the ISR also clears it. */
+ ret = vdev->isr;
+ vdev->isr = 0;
+ virtio_update_irq(vdev);
+ break;
+ case VIRTIO_PCI_CONFIG_LEN:
+ ret = vdev->config_len;
+ break;
+ case VIRTIO_PCI_CONFIG_PFN:
+ ret = vdev->config_pfn;
+ break;
+ default:
+ break;
+ }
+
+ return ret;
+}
+
+static void virtio_map(PCIDevice *pci_dev, int region_num,
+ uint32_t addr, uint32_t size, int type)
+{
+ VirtIODevice *vdev = to_virtio_device(pci_dev);
+
+ vdev->addr = addr;
+ register_ioport_write(addr, size, 1, virtio_ioport_write, vdev);
+ register_ioport_write(addr, size, 2, virtio_ioport_write, vdev);
+ register_ioport_write(addr, size, 4, virtio_ioport_write, vdev);
+ register_ioport_read(addr, size, 1, virtio_ioport_read, vdev);
+ register_ioport_read(addr, size, 2, virtio_ioport_read, vdev);
+ register_ioport_read(addr, size, 4, virtio_ioport_read, vdev);
+}
+
+VirtQueue *virtio_add_queue(VirtIODevice *vdev,
+ void (*handle_output)(VirtIODevice *, VirtQueue *))
+{
+ int i;
+
+ for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
+ if (vdev->vq[i].vring.num == 0)
+ break;
+ }
+
+ /* FIXME bug_on i == VIRTIO_PCI_QUEUE_MAX */
+
+ vdev->vq[i].vring.num = VIRTQUEUE_MAX_SIZE;
+ vdev->vq[i].handle_output = handle_output;
+ vdev->vq[i].index = i;
+
+ return &vdev->vq[i];
+}
+
+void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
+{
+ if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
+ return;
+
+ vdev->isr = 1;
+ virtio_update_irq(vdev);
+}
+
+VirtIODevice *virtio_init_pci(PCIBus *bus, const char *name,
+ uint16_t vendor, uint16_t device,
+ uint16_t subvendor, uint16_t subdevice,
+ size_t config_size, size_t struct_size)
+{
+ VirtIODevice *vdev;
+ PCIDevice *pci_dev;
+ uint8_t *config;
+
+ pci_dev = pci_register_device(bus, name, struct_size,
+ -1, NULL, NULL);
+ vdev = to_virtio_device(pci_dev);
+
+ vdev->status = 0;
+ vdev->isr = 0;
+ vdev->queue_sel = 0;
+ memset(vdev->vq, 0, sizeof(vdev->vq));
+
+ config = pci_dev->config;
+ config[0x00] = vendor & 0xFF;
+ config[0x01] = (vendor >> 8) & 0xFF;
+ config[0x02] = device & 0xFF;
+ config[0x03] = (device >> 8) & 0xFF;
+
+ config[0x09] = 0x00;
+ config[0x0a] = 0x00;
+ config[0x0b] = 0x05;
+ config[0x0e] = 0x00;
+
+ config[0x2c] = subvendor & 0xFF;
+ config[0x2d] = (subvendor >> 8) & 0xFF;
+ config[0x2e] = subdevice & 0xFF;
+ config[0x2f] = (subdevice >> 8) & 0xFF;
+
+ config[0x3d] = 1;
+
+ vdev->name = name;
+ vdev->config_len = config_size;
+
+ pci_register_io_region(pci_dev, 0, 28, PCI_ADDRESS_SPACE_IO, virtio_map);
+
+ return vdev;
+}
diff --git a/qemu/hw/virtio.h b/qemu/hw/virtio.h
new file mode 100644
index 0000000..44d1245
--- /dev/null
+++ b/qemu/hw/virtio.h
@@ -0,0 +1,136 @@
+/*
+ * Virtio Support
+ *
+ * Copyright IBM, Corp. 2007
+ *
+ * Authors:
+ * Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef _QEMU_VIRTIO_H
+#define _QEMU_VIRTIO_H
+
+/* from Linux's linux/virtio_config.h */
+
+/* Status byte for guest to report progress, and synchronize features. */
+/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
+#define VIRTIO_CONFIG_S_ACKNOWLEDGE 1
+/* We have found a driver for the device. */
+#define VIRTIO_CONFIG_S_DRIVER 2
+/* Driver has used its parts of the config, and is happy */
+#define VIRTIO_CONFIG_S_DRIVER_OK 4
+/* We've given up on this device. */
+#define VIRTIO_CONFIG_S_FAILED 0x80
+
+/* from Linux's linux/virtio_ring.h */
+
+/* This marks a buffer as continuing via the next field. */
+#define VRING_DESC_F_NEXT 1
+/* This marks a buffer as write-only (otherwise read-only). */
+#define VRING_DESC_F_WRITE 2
+
+/* This means don't notify other side when buffer added. */
+#define VRING_USED_F_NO_NOTIFY 1
+/* This means don't interrupt guest when buffer consumed. */
+#define VRING_AVAIL_F_NO_INTERRUPT 1
+
+typedef struct VirtQueue VirtQueue;
+
+typedef struct VRingDesc
+{
+ uint64_t addr;
+ uint32_t len;
+ uint16_t flags;
+ uint16_t next;
+} VRingDesc;
+
+typedef struct VRingAvail
+{
+ uint16_t flags;
+ uint16_t idx;
+ uint16_t ring[0];
+} VRingAvail;
+
+typedef struct VRingUsedElem
+{
+ uint32_t id;
+ uint32_t len;
+} VRingUsedElem;
+
+typedef struct VRingUsed
+{
+ uint16_t flags;
+ uint16_t idx;
+ VRingUsedElem ring[0];
+} VRingUsed;
+
+typedef struct VRing
+{
+ unsigned int num;
+ VRingDesc *desc;
+ VRingAvail *avail;
+ VRingUsed *used;
+} VRing;
+
+struct VirtQueue
+{
+ VRing vring;
+ uint32_t pfn;
+ uint16_t last_avail_idx;
+ void (*handle_output)(VirtIODevice *vdev, VirtQueue *vq);
+ int index;
+};
+
+#define VIRTQUEUE_MAX_SIZE 127
+
+typedef struct VirtQueueElement
+{
+ unsigned int index;
+ unsigned int out_num;
+ unsigned int in_num;
+ struct iovec in_sg[VIRTQUEUE_MAX_SIZE];
+ struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
+} VirtQueueElement;
+
+#define VIRTIO_PCI_QUEUE_MAX 16
+
+struct VirtIODevice
+{
+ PCIDevice pci_dev;
+ const char *name;
+ uint32_t addr;
+ uint16_t vendor;
+ uint16_t device;
+ uint8_t status;
+ uint8_t isr;
+ uint16_t queue_sel;
+ uint32_t features;
+ uint32_t config_pfn;
+ uint32_t config_len;
+ uint32_t (*get_features)(VirtIODevice *vdev);
+ void (*set_features)(VirtIODevice *vdev, uint32_t val);
+ void (*update_config)(VirtIODevice *vdev, uint8_t *config);
+ VirtQueue vq[VIRTIO_PCI_QUEUE_MAX];
+};
+
+VirtIODevice *virtio_init_pci(PCIBus *bus, const char *name,
+ uint16_t vendor, uint16_t device,
+ uint16_t subvendor, uint16_t subdevice,
+ size_t config_size, size_t struct_size);
+
+VirtQueue *virtio_add_queue(VirtIODevice *vdev,
+ void (*handle_output)(VirtIODevice *,
+ VirtQueue *));
+
+void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
+ unsigned int len);
+
+int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem);
+
+void virtio_notify(VirtIODevice *vdev, VirtQueue *vq);
+
+#endif
diff --git a/qemu/vl.h b/qemu/vl.h
index 01aeabc..fafcf09 100644
--- a/qemu/vl.h
+++ b/qemu/vl.h
@@ -1392,6 +1392,10 @@ typedef struct ADBDevice ADBDevice;
void pci_hypercall_init(PCIBus *bus);
void vmchannel_init(CharDriverState *hd, uint32_t deviceid, uint32_t index);

+/* virtio.c */
+
+typedef struct VirtIODevice VirtIODevice;
+
/* buf = NULL means polling */
typedef int ADBDeviceRequest(ADBDevice *d, uint8_t *buf_out,
const uint8_t *buf, int len);