virtio.h

#pragma once
#include "common.h"

#define VIRTQ_ENTRY_NUM 16
#define VIRTIO_DEVICE_NET 1
#define VIRTIO_DEVICE_BLK 2
#define VIRTIO_REG_MAGIC 0x00
#define VIRTIO_REG_VERSION       0x04
#define VIRTIO_REG_DEVICE_ID     0x08
#define VIRTIO_REG_DEVICE_FEATURES 0x10
#define VIRTIO_REG_DRIVER_FEATURES 0x20
#define VIRTIO_REG_GUEST_PAGE_SIZE 0x28
#define VIRTIO_REG_QUEUE_SEL     0x30
#define VIRTIO_REG_QUEUE_NUM_MAX 0x34
#define VIRTIO_REG_QUEUE_NUM     0x38
#define VIRTIO_REG_QUEUE_ALIGN   0x3c
#define VIRTIO_REG_QUEUE_PFN     0x40
#define VIRTIO_REG_QUEUE_READY   0x44
#define VIRTIO_REG_QUEUE_NOTIFY  0x50
#define VIRTIO_REG_DEVICE_STATUS 0x70
#define VIRTIO_REG_DEVICE_CONFIG 0x100
#define VIRTIO_STATUS_ACK       1
#define VIRTIO_STATUS_DRIVER    2
#define VIRTIO_STATUS_DRIVER_OK 4
#define VIRTIO_STATUS_FEAT_OK   8
#define VIRTQ_DESC_F_NEXT          1
#define VIRTQ_DESC_F_WRITE         2
#define VIRTQ_AVAIL_F_NO_INTERRUPT 1

struct virtq_desc {
  uint64_t addr; // guest physical address
  uint32_t len; // data length
  uint16_t flags; // 0x1: is next, 0x2: is write only, 0x4: is indirect
  uint16_t next; // next descriptor index
} __attribute__((packed));

struct virtq_avail {
  uint16_t flags;
  uint16_t index;
  uint16_t ring[VIRTQ_ENTRY_NUM];
} __attribute__((packed));

struct virtq_used_elem {
  uint32_t id;
  uint32_t len;
} __attribute__((packed));

struct virtq_used {
  uint16_t flags;
  uint16_t index;
  struct virtq_used_elem ring[VIRTQ_ENTRY_NUM];
} __attribute__((packed));

struct virtio_virtq {
  struct virtq_desc descs[VIRTQ_ENTRY_NUM];
  struct virtq_avail avail;
  struct virtq_used used __attribute__((aligned(4096)));
  int queue_index;
  volatile uint16_t *used_index;
  uint16_t last_used_index;
} __attribute__((packed));