Re: [PATCH] [PATCH 1/3] virtio infrastructure

[Anthony Liguori <anthony-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org>]

Dor Laor wrote:
> Anthony Liguori wrote:
>   
>> Hi Dor,
>>
>> I can't tell if you made any changes to this series.  I have to look 
>> back to my notes, but I believe it would be okay to pull this series 
>> into KVM.  I still need to spend some time updating the patchset to be 
>> more friendly for QEMU though before resubmitting to qemu-devel.  Any 
>> help on making it more cross-architecture friendly would be appreciated!
>>
>>     
> Hi,
>
> I didn't do any change (except maybe very very minor adjustments for it 
> to match existing version, nothing risky).
> The reason I sent it as it is + non-qemu-standard performance 
> optimization is to finally have descent performance for KVM IO.
> My next step is to add backward compatibility support for older guests 
> and then to implement host kernel module for network.
>   

I have backports up to 2.6.18 although I need to write the awk scripts 
to make it automatic.  If you can wait until the middle of the week when 
I get back into the office, I'll post it.

Regards,

Anthony Liguori

> I hope that someone will pick up the qemu part since it's important too, 
> especially the block device and new devices too.
> There is also work in progress to move the balloon driver over virtio.
> Thanks,
> Dor.
>   
>> Regards,
>>
>> Anthony Liguori
>>
>> Dor.Laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org wrote:
>>     
>>> From: Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>>>
>>> This patch implements the basic infrastructure for virtio devices.  
>>> These
>>> devices are exposed to the guest as real PCI devices.  The PCI 
>>> vendor/device
>>> IDs have been donated by Qumranet and the subsystem IDs are used to 
>>> distinguish
>>> the virtio device itself.
>>>
>>> Virtio provides an abstraction for performing guest=>host and 
>>> host=>guest
>>> communications.  It also provides a standard ring queue interface and 
>>> discovery
>>> mechanism.  Finally, virtio provides a simple mechanism for passing
>>> configuration between host and guest.
>>>
>>> In this virtio implementation, we provide these things via normal PCI
>>> operations.  The Linux kernel support for this virtio device is 
>>> pending in
>>> Rusty's virtio patch queue[1].  They should be submitted once the 
>>> merge window
>>> opens again.
>>>
>>> Some future TODOs are to use endian/alignment safe routines when 
>>> accessing the
>>> virtqueue so that mixed mode host/guests are supported.
>>>
>>> [1] http://ozlabs.org/~rusty/kernel/hg
>>>
>>> Signed-off-by: Anthony Liguori <aliguori-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
>>> Cc: Rusty Russell <rusty-8n+1lVoiYb80n/F98K4Iww@public.gmane.org>
>>> Cc: Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>>> Cc: Dor Laor <dor.laor-atKUWr5tajBWk0Htik3J/w@public.gmane.org>
>>> ---
>>>  qemu/Makefile.target |    3 +
>>>  qemu/hw/virtio.c     |  422 
>>> ++++++++++++++++++++++++++++++++++++++++++++++++++
>>>  qemu/hw/virtio.h     |  143 +++++++++++++++++
>>>  3 files changed, 568 insertions(+), 0 deletions(-)
>>>  create mode 100644 qemu/hw/virtio.c
>>>  create mode 100644 qemu/hw/virtio.h
>>>
>>> diff --git a/qemu/Makefile.target b/qemu/Makefile.target
>>> index 12fb043..8b5853b 100644
>>> --- a/qemu/Makefile.target
>>> +++ b/qemu/Makefile.target
>>> @@ -463,6 +463,9 @@ 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
>>> diff --git a/qemu/hw/virtio.c b/qemu/hw/virtio.c
>>> new file mode 100644
>>> index 0000000..6a1d380
>>> --- /dev/null
>>> +++ b/qemu/hw/virtio.c
>>> @@ -0,0 +1,422 @@
>>> +/*
>>> + * 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 <inttypes.h>
>>> +#include <err.h>
>>> +
>>> +#include "virtio.h"
>>> +#include "sysemu.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
>>> +
>>> +#define VIRTIO_PCI_CONFIG        20
>>> +
>>> +/* QEMU doesn't strictly need write barriers since everything runs in
>>> + * lock-step.  We'll leave the calls to wmb() in though to make it 
>>> obvious for
>>> + * KVM or if kqemu gets SMP support.
>>> + */
>>> +#define wmb() do { } while (0)
>>> +
>>> +/* virt queue functions */
>>> +
>>> +static void virtqueue_init(VirtQueue *vq, void *p)
>>> +{
>>> +    vq->vring.desc = p;
>>> +    vq->vring.avail = p + vq->vring.num * sizeof(VRingDesc);
>>> +    vq->vring.used = (void *)TARGET_PAGE_ALIGN((unsigned 
>>> long)&vq->vring.avail->ring[vq->vring.num]);
>>> +}
>>> +
>>> +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;
>>> +    }
>>> +}
>>> +
>>> +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;
>>> +    default:
>>> +    break;
>>> +    }
>>> +
>>> +    return ret;
>>> +}
>>> +
>>> +static uint32_t virtio_config_readb(void *opaque, uint32_t addr)
>>> +{
>>> +    VirtIODevice *vdev = opaque;
>>> +    uint8_t val;
>>> +
>>> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
>>> +    if (addr > (vdev->config_len - sizeof(val)))
>>> +    return (uint32_t)-1;
>>> +
>>> +    memcpy(&val, vdev->config + addr, sizeof(val));
>>> +    return val;
>>> +}
>>> +
>>> +static uint32_t virtio_config_readw(void *opaque, uint32_t addr)
>>> +{
>>> +    VirtIODevice *vdev = opaque;
>>> +    uint16_t val;
>>> +
>>> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
>>> +    if (addr > (vdev->config_len - sizeof(val)))
>>> +    return (uint32_t)-1;
>>> +
>>> +    memcpy(&val, vdev->config + addr, sizeof(val));
>>> +    return val;
>>> +}
>>> +
>>> +static uint32_t virtio_config_readl(void *opaque, uint32_t addr)
>>> +{
>>> +    VirtIODevice *vdev = opaque;
>>> +    uint32_t val;
>>> +
>>> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
>>> +    if (addr > (vdev->config_len - sizeof(val)))
>>> +    return (uint32_t)-1;
>>> +
>>> +    memcpy(&val, vdev->config + addr, sizeof(val));
>>> +    return val;
>>> +}
>>> +
>>> +static void virtio_config_writeb(void *opaque, uint32_t addr, 
>>> uint32_t data)
>>> +{
>>> +    VirtIODevice *vdev = opaque;
>>> +    uint8_t val = data;
>>> +
>>> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
>>> +    if (addr > (vdev->config_len - sizeof(val)))
>>> +    return;
>>> +
>>> +    memcpy(vdev->config + addr, &val, sizeof(val));
>>> +}
>>> +
>>> +static void virtio_config_writew(void *opaque, uint32_t addr, 
>>> uint32_t data)
>>> +{
>>> +    VirtIODevice *vdev = opaque;
>>> +    uint16_t val = data;
>>> +
>>> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
>>> +    if (addr > (vdev->config_len - sizeof(val)))
>>> +    return;
>>> +
>>> +    memcpy(vdev->config + addr, &val, sizeof(val));
>>> +}
>>> +
>>> +static void virtio_config_writel(void *opaque, uint32_t addr, 
>>> uint32_t data)
>>> +{
>>> +    VirtIODevice *vdev = opaque;
>>> +    uint32_t val = data;
>>> +
>>> +    addr -= vdev->addr + VIRTIO_PCI_CONFIG;
>>> +    if (addr > (vdev->config_len - sizeof(val)))
>>> +    return;
>>> +
>>> +    memcpy(vdev->config + addr, &val, sizeof(val));
>>> +}
>>> +
>>> +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);
>>> +    int i;
>>> +
>>> +    vdev->addr = addr;
>>> +    for (i = 0; i < 3; i++) {
>>> +    register_ioport_write(addr, 20, 1 << i, virtio_ioport_write, vdev);
>>> +    register_ioport_read(addr, 20, 1 << i, virtio_ioport_read, vdev);
>>> +    }
>>> +
>>> +    if (vdev->config_len) {
>>> +    register_ioport_write(addr + 20, vdev->config_len, 1,
>>> +                  virtio_config_writeb, vdev);
>>> +    register_ioport_write(addr + 20, vdev->config_len, 2,
>>> +                  virtio_config_writew, vdev);
>>> +    register_ioport_write(addr + 20, vdev->config_len, 4,
>>> +                  virtio_config_writel, vdev);
>>> +    register_ioport_read(addr + 20, vdev->config_len, 1,
>>> +                 virtio_config_readb, vdev);
>>> +    register_ioport_read(addr + 20, vdev->config_len, 2,
>>> +                 virtio_config_readw, vdev);
>>> +    register_ioport_read(addr + 20, vdev->config_len, 4,
>>> +                 virtio_config_readl, vdev);
>>> +
>>> +    vdev->update_config(vdev, vdev->config);
>>> +    }
>>> +}
>>> +
>>> +VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
>>> +                void (*handle_output)(VirtIODevice *, VirtQueue *))
>>> +{
>>> +    int i;
>>> +
>>> +    for (i = 0; i < VIRTIO_PCI_QUEUE_MAX; i++) {
>>> +    if (vdev->vq[i].vring.num == 0)
>>> +        break;
>>> +    }
>>> +
>>> +    if (i == VIRTIO_PCI_QUEUE_MAX || queue_size > VIRTQUEUE_MAX_SIZE)
>>> +    abort();
>>> +
>>> +    vdev->vq[i].vring.num = queue_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,
>>> +                  uint8_t class_code, uint8_t subclass_code,
>>> +                  uint8_t pif, 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] = pif;
>>> +    config[0x0a] = subclass_code;
>>> +    config[0x0b] = class_code;
>>> +    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;
>>> +    if (vdev->config_len)
>>> +    vdev->config = qemu_mallocz(config_size);
>>> +    else
>>> +    vdev->config = NULL;
>>> +
>>> +    pci_register_io_region(pci_dev, 0, 20 + config_size, 
>>> 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..dee97ba
>>> --- /dev/null
>>> +++ b/qemu/hw/virtio.h
>>> @@ -0,0 +1,143 @@
>>> +/*
>>> + * 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
>>> +
>>> +#include <sys/uio.h>
>>> +#include "hw.h"
>>> +#include "pci.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 VirtIODevice VirtIODevice;
>>> +
>>> +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 1024
>>> +
>>> +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;
>>> +    size_t config_len;
>>> +    void *config;
>>> +    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,
>>> +                  uint8_t class_code, uint8_t subclass_code,
>>> +                  uint8_t pif, size_t config_size,
>>> +                  size_t struct_size);
>>> +
>>> +VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
>>> +                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
>>>   
>>>       
>>     
>
>
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