1 files changed, 72 insertions, 0 deletions
diff --git a/kernel/virtio.h b/kernel/virtio.h
new file mode 100644
index 0000000..03b53a9
--- /dev/null
+++ b/kernel/virtio.h
@@ -0,0 +1,72 @@
+//
+// virtio device definitions.
+// for both the mmio interface, and virtio descriptors.
+// only tested with qemu.
+// this is the "legacy" virtio interface.
+//
+// the virtio spec:
+// https://docs.oasis-open.org/virtio/virtio/v1.1/virtio-v1.1.pdf
+//
+
+// virtio mmio control registers, mapped starting at 0x10001000.
+// from qemu virtio_mmio.h
+#define VIRTIO_MMIO_MAGIC_VALUE		0x000 // 0x74726976
+#define VIRTIO_MMIO_VERSION		0x004 // version; 1 is legacy
+#define VIRTIO_MMIO_DEVICE_ID		0x008 // device type; 1 is net, 2 is disk
+#define VIRTIO_MMIO_VENDOR_ID		0x00c // 0x554d4551
+#define VIRTIO_MMIO_DEVICE_FEATURES	0x010
+#define VIRTIO_MMIO_DRIVER_FEATURES	0x020
+#define VIRTIO_MMIO_GUEST_PAGE_SIZE	0x028 // page size for PFN, write-only
+#define VIRTIO_MMIO_QUEUE_SEL		0x030 // select queue, write-only
+#define VIRTIO_MMIO_QUEUE_NUM_MAX	0x034 // max size of current queue, read-only
+#define VIRTIO_MMIO_QUEUE_NUM		0x038 // size of current queue, write-only
+#define VIRTIO_MMIO_QUEUE_ALIGN		0x03c // used ring alignment, write-only
+#define VIRTIO_MMIO_QUEUE_PFN		0x040 // physical page number for queue, read/write
+#define VIRTIO_MMIO_QUEUE_READY		0x044 // ready bit
+#define VIRTIO_MMIO_QUEUE_NOTIFY	0x050 // write-only
+#define VIRTIO_MMIO_INTERRUPT_STATUS	0x060 // read-only
+#define VIRTIO_MMIO_INTERRUPT_ACK	0x064 // write-only
+#define VIRTIO_MMIO_STATUS		0x070 // read/write
+
+// status register bits, from qemu virtio_config.h
+#define VIRTIO_CONFIG_S_ACKNOWLEDGE	1
+#define VIRTIO_CONFIG_S_DRIVER		2
+#define VIRTIO_CONFIG_S_DRIVER_OK	4
+#define VIRTIO_CONFIG_S_FEATURES_OK	8
+
+// device feature bits
+#define VIRTIO_BLK_F_RO              5	/* Disk is read-only */
+#define VIRTIO_BLK_F_SCSI            7	/* Supports scsi command passthru */
+#define VIRTIO_BLK_F_CONFIG_WCE     11	/* Writeback mode available in config */
+#define VIRTIO_BLK_F_MQ             12	/* support more than one vq */
+#define VIRTIO_F_ANY_LAYOUT         27
+#define VIRTIO_RING_F_INDIRECT_DESC 28
+#define VIRTIO_RING_F_EVENT_IDX     29
+
+// this many virtio descriptors.
+// must be a power of two.
+#define NUM 8
+
+struct VRingDesc {
+  uint64 addr;
+  uint32 len;
+  uint16 flags;
+  uint16 next;
+};
+#define VRING_DESC_F_NEXT  1 // chained with another descriptor
+#define VRING_DESC_F_WRITE 2 // device writes (vs read)
+
+struct VRingUsedElem {
+  uint32 id;   // index of start of completed descriptor chain
+  uint32 len;
+};
+
+// for disk ops
+#define VIRTIO_BLK_T_IN  0 // read the disk
+#define VIRTIO_BLK_T_OUT 1 // write the disk
+
+struct UsedArea {
+  uint16 flags;
+  uint16 id;
+  struct VRingUsedElem elems[NUM];
+};