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virtio cleanup #5

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virtio cleanup #5

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aaa10d9
clean up virtio
xiw Sep 27, 2019
2eeea38
convert tabs to spaces in virtio.h
xiw Sep 27, 2019
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76 changes: 40 additions & 36 deletions kernel/virtio.h
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -10,53 +10,57 @@

// 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
#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
#define VIRTIO_MMIO_CONFIG 0x100 // configuration space

// 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
#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_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 {
struct virtq_desc {
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)
#define VIRTQ_DESC_F_NEXT 1 // chained with another descriptor
#define VIRTQ_DESC_F_WRITE 2 // device writes (vs read)

struct virtq_avail {
uint16 flags;
uint16 idx;
uint16 ring[];
};
#define VIRTQ_AVAIL_F_NO_INTERRUPT 1 // suppress interrupts

struct VRingUsedElem {
struct virtq_used_elem {
uint32 id; // index of start of completed descriptor chain
uint32 len;
};
Expand All @@ -65,8 +69,8 @@ struct VRingUsedElem {
#define VIRTIO_BLK_T_IN 0 // read the disk
#define VIRTIO_BLK_T_OUT 1 // write the disk

struct UsedArea {
struct virtq_used {
uint16 flags;
uint16 id;
struct VRingUsedElem elems[NUM];
uint16 idx;
struct virtq_used_elem ring[];
};
45 changes: 24 additions & 21 deletions kernel/virtio_disk.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,20 +20,24 @@
// the address of virtio mmio register r.
#define R(n, r) ((volatile uint32 *)(VIRTION(n) + (r)))

// this many virtio descriptors.
// must be a power of two.
#define NUM 8

struct disk {
// memory for virtio descriptors &c for queue 0.
// this is a global instead of allocated because it has
// to be multiple contiguous pages, which kalloc()
// doesn't support.
char pages[2*PGSIZE];

struct VRingDesc *desc;
uint16 *avail;
struct UsedArea *used;
struct virtq_desc *desc;
struct virtq_avail *avail;
struct virtq_used *used;

// our own book-keeping.
char free[NUM]; // is a descriptor free?
uint16 used_idx; // we've looked this far in used[2..NUM].
uint16 used_idx; // we've looked this far in used->ring.

// track info about in-flight operations,
// for use when completion interrupt arrives.
Expand Down Expand Up @@ -109,13 +113,13 @@ virtio_disk_init(int n)
memset(disk[n].pages, 0, sizeof(disk[n].pages));
*R(n, VIRTIO_MMIO_QUEUE_PFN) = ((uint64)disk[n].pages) >> PGSHIFT;

// desc = pages -- num * VRingDesc
// desc = pages -- num * virtq_desc
// avail = pages + 0x40 -- 2 * uint16, then num * uint16
// used = pages + 4096 -- 2 * uint16, then num * vRingUsedElem
// used = pages + 4096 -- 2 * uint16, then num * virtq_used_elem

disk[n].desc = (struct VRingDesc *) disk[n].pages;
disk[n].avail = (uint16*)(((char*)disk[n].desc) + NUM*sizeof(struct VRingDesc));
disk[n].used = (struct UsedArea *) (disk[n].pages + PGSIZE);
disk[n].desc = (struct virtq_desc *) disk[n].pages;
disk[n].avail = (struct virtq_avail *)(((char*)disk[n].desc) + NUM*sizeof(struct virtq_desc));
disk[n].used = (struct virtq_used *) (disk[n].pages + PGSIZE);

for(int i = 0; i < NUM; i++)
disk[n].free[i] = 1;
Expand Down Expand Up @@ -156,7 +160,7 @@ free_chain(int n, int i)
{
while(1){
free_desc(n, i);
if(disk[n].desc[i].flags & VRING_DESC_F_NEXT)
if(disk[n].desc[i].flags & VIRTQ_DESC_F_NEXT)
i = disk[n].desc[i].next;
else
break;
Expand Down Expand Up @@ -217,35 +221,34 @@ virtio_disk_rw(int n, struct buf *b, int write)
// thus the call to kvmpa().
disk[n].desc[idx[0]].addr = (uint64) kvmpa((uint64) &buf0);
disk[n].desc[idx[0]].len = sizeof(buf0);
disk[n].desc[idx[0]].flags = VRING_DESC_F_NEXT;
disk[n].desc[idx[0]].flags = VIRTQ_DESC_F_NEXT;
disk[n].desc[idx[0]].next = idx[1];

disk[n].desc[idx[1]].addr = (uint64) b->data;
disk[n].desc[idx[1]].len = BSIZE;
if(write)
disk[n].desc[idx[1]].flags = 0; // device reads b->data
else
disk[n].desc[idx[1]].flags = VRING_DESC_F_WRITE; // device writes b->data
disk[n].desc[idx[1]].flags |= VRING_DESC_F_NEXT;
disk[n].desc[idx[1]].flags = VIRTQ_DESC_F_WRITE; // device writes b->data
disk[n].desc[idx[1]].flags |= VIRTQ_DESC_F_NEXT;
disk[n].desc[idx[1]].next = idx[2];

disk[n].info[idx[0]].status = 0;
disk[n].desc[idx[2]].addr = (uint64) &disk[n].info[idx[0]].status;
disk[n].desc[idx[2]].len = 1;
disk[n].desc[idx[2]].flags = VRING_DESC_F_WRITE; // device writes the status
disk[n].desc[idx[2]].flags = VIRTQ_DESC_F_WRITE; // device writes the status
disk[n].desc[idx[2]].next = 0;

// record struct buf for virtio_disk_intr().
b->disk = 1;
disk[n].info[idx[0]].b = b;

// avail[0] is flags
// avail[1] tells the device how far to look in avail[2...].
// avail[2...] are desc[] indices the device should process.
// avail->idx tells the device how far to look in avail->ring.
// avail->ring[...] are desc[] indices the device should process.
// we only tell device the first index in our chain of descriptors.
disk[n].avail[2 + (disk[n].avail[1] % NUM)] = idx[0];
disk[n].avail->ring[disk[n].avail->idx % NUM] = idx[0];
__sync_synchronize();
disk[n].avail[1] = disk[n].avail[1] + 1;
disk[n].avail->idx += 1;

*R(n, VIRTIO_MMIO_QUEUE_NOTIFY) = 0; // value is queue number

Expand All @@ -265,8 +268,8 @@ virtio_disk_intr(int n)
{
acquire(&disk[n].vdisk_lock);

while((disk[n].used_idx % NUM) != (disk[n].used->id % NUM)){
int id = disk[n].used->elems[disk[n].used_idx].id;
while((disk[n].used_idx % NUM) != (disk[n].used->idx % NUM)){
int id = disk[n].used->ring[disk[n].used_idx].id;

if(disk[n].info[id].status != 0)
panic("virtio_disk_intr status");
Expand Down