virtio详细介绍和1.1新功能

/* Virtio ring descriptors: 16 bytes.  These can chain together via "next". */
struct vring_desc {
    /* Address (guest-physical). */
    __virtio64 addr;
    /* Length. */
    __virtio32 len;
    /* The flags as indicated above. */
    __virtio16 flags;
    /* We chain unused descriptors via this, too */
    __virtio16 next;
};
 
struct vring_avail {
    __virtio16 flags;
    __virtio16 idx;
    __virtio16 ring[];
};
 
/* uint32_t is used here for ids for padding reasons. */
struct vring_used_elem {
    /* Index of start of used descriptor chain. */
    __virtio32 id;
    /* Total length of the descriptor chain which was used (written to) */
    __virtio32 len;
};
 
typedef struct vring_used_elem __attribute__((aligned(VRING_USED_ALIGN_SIZE)))
    vring_used_elem_t;
 
struct vring_used {
    __virtio16 flags;
    __virtio16 idx;
    vring_used_elem_t ring[];
};

typedef struct VirtIOPCIRegion {
    MemoryRegion mr;
    uint32_t offset;
    uint32_t size;
    uint32_t type;
} VirtIOPCIRegion;
 
typedef struct VirtIOPCIQueue {
  uint16_t num;
  bool enabled;
  uint32_t desc[2];
  uint32_t avail[2];
  uint32_t used[2];
} VirtIOPCIQueue;
 
struct VirtIOPCIProxy {
    PCIDevice pci_dev;
    MemoryRegion bar;
    union {
        struct {
            VirtIOPCIRegion common;
            VirtIOPCIRegion isr;
            VirtIOPCIRegion device;
            VirtIOPCIRegion notify;
            VirtIOPCIRegion notify_pio;
        };
        VirtIOPCIRegion regs[5];
    };
    MemoryRegion modern_bar;
    MemoryRegion io_bar;
    uint32_t legacy_io_bar_idx;
    uint32_t msix_bar_idx;
    uint32_t modern_io_bar_idx;
    uint32_t modern_mem_bar_idx;
    int config_cap;
    uint32_t flags;
    bool disable_modern;
    bool ignore_backend_features;
    OnOffAuto disable_legacy;
    uint32_t class_code;
    uint32_t nvectors;
    uint32_t dfselect;
    uint32_t gfselect;
    uint32_t guest_features[2];
    VirtIOPCIQueue vqs[VIRTIO_QUEUE_MAX];
 
    VirtIOIRQFD *vector_irqfd;
    int nvqs_with_notifiers;
    VirtioBusState bus;
};

static void virtio_pci_modern_regions_init(VirtIOPCIProxy *proxy,
                                           const char *vdev_name)
{
    static const MemoryRegionOps common_ops = {
        .read = virtio_pci_common_read,
        .write = virtio_pci_common_write,
        .impl = {
            .min_access_size = 1,
            .max_access_size = 4,
        },
        .endianness = DEVICE_LITTLE_ENDIAN,
    };
    g_string_printf(name, "virtio-pci-common-%s", vdev_name);
    memory_region_init_io(&proxy->common.mr, OBJECT(proxy),
                          &common_ops,
                          proxy,
                          name->str,
                          proxy->common.size);
}
static void virtio_pci_common_write(void *opaque, hwaddr addr,
                                    uint64_t val, unsigned size)
{
    VirtIOPCIProxy *proxy = opaque;
    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
 
    switch (addr) {
    case VIRTIO_PCI_COMMON_DFSELECT:
        proxy->dfselect = val;
        break;
    case VIRTIO_PCI_COMMON_GFSELECT:
        proxy->gfselect = val;
        break;
    
    default:
        break;
    }
}

struct VirtIONetPCI {
    VirtIOPCIProxy parent_obj;
    VirtIONet vdev;
};

/* This header comes first in the scatter-gather list.
 * For legacy virtio, if VIRTIO_F_ANY_LAYOUT is not negotiated, it must
 * be the first element of the scatter-gather list.  If you don't
 * specify GSO or CSUM features, you can simply ignore the header. */
struct virtio_net_hdr {
    /* See VIRTIO_NET_HDR_F_* */
    uint8_t flags;
    /* See VIRTIO_NET_HDR_GSO_* */
    uint8_t gso_type;
    __virtio16 hdr_len;     /* Ethernet + IP + tcp/udp hdrs */
    __virtio16 gso_size;        /* Bytes to append to hdr_len per frame */
    __virtio16 csum_start;  /* Position to start checksumming from */
    __virtio16 csum_offset; /* Offset after that to place checksum */
};

/*
 * Control virtqueue data structures
 *
 * The control virtqueue expects a header in the first sg entry
 * and an ack/status response in the last entry.  Data for the
 * command goes in between.
 */
struct virtio_net_ctrl_hdr {
    uint8_t class;
    uint8_t cmd;
} QEMU_PACKED;

struct vring_packed_desc {
    /* Buffer Address. */
    uint64_t addr;
    /* Buffer Length. */
    uint32_t len;
    /* Buffer ID. */
    uint16_t id;
    /* The flags depending on descriptor type. */
    uint16_t flags;
};