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Wrap state of disk driver in a struct so that it is easier to support

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several disks (e.g., in a mount lab).
This commit is contained in:
Frans Kaashoek 2019-08-12 07:20:32 -04:00
parent d96a8c5661
commit e398a9815c
1 changed files with 69 additions and 67 deletions
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136
kernel/virtio_disk.c
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@ -20,36 +20,38 @@
// the address of virtio mmio register r. // the address of virtio mmio register r.
#define R(r) ((volatile uint32 *)(VIRTIO0 + (r))) #define R(r) ((volatile uint32 *)(VIRTIO0 + (r)))
struct spinlock vdisk_lock; static struct disk {
// memory for virtio descriptors &c for queue 0.
// this is a global instead of allocated because it must
// be multiple contiguous pages, which kalloc()
// doesn't support, and page aligned.
char pages[2*PGSIZE];
struct VRingDesc *desc;
uint16 *avail;
struct UsedArea *used;
// memory for virtio descriptors &c for queue 0. // our own book-keeping.
// this is a global instead of allocated because it has char free[NUM]; // is a descriptor free?
// to be multiple contiguous pages, which kalloc() uint16 used_idx; // we've looked this far in used[2..NUM].
// doesn't support.
__attribute__ ((aligned (PGSIZE)))
static char pages[2*PGSIZE];
static struct VRingDesc *desc;
static uint16 *avail;
static struct UsedArea *used;
// our own book-keeping. // track info about in-flight operations,
static char free[NUM]; // is a descriptor free? // for use when completion interrupt arrives.
static uint16 used_idx; // we've looked this far in used[2..NUM]. // indexed by first descriptor index of chain.
struct {
// track info about in-flight operations, struct buf *b;
// for use when completion interrupt arrives. char status;
// indexed by first descriptor index of chain. } info[NUM];
static struct {
struct buf *b; struct spinlock vdisk_lock;
char status;
} info[NUM]; } __attribute__ ((aligned (PGSIZE))) disk;
void void
virtio_disk_init(void) virtio_disk_init(void)
{ {
uint32 status = 0; uint32 status = 0;
initlock(&vdisk_lock, "virtio_disk"); initlock(&disk.vdisk_lock, "virtio_disk");
if(*R(VIRTIO_MMIO_MAGIC_VALUE) != 0x74726976 || if(*R(VIRTIO_MMIO_MAGIC_VALUE) != 0x74726976 ||
*R(VIRTIO_MMIO_VERSION) != 1 || *R(VIRTIO_MMIO_VERSION) != 1 ||
@ -93,19 +95,19 @@ virtio_disk_init(void)
if(max < NUM) if(max < NUM)
panic("virtio disk max queue too short"); panic("virtio disk max queue too short");
*R(VIRTIO_MMIO_QUEUE_NUM) = NUM; *R(VIRTIO_MMIO_QUEUE_NUM) = NUM;
memset(pages, 0, sizeof(pages)); memset(disk.pages, 0, sizeof(disk.pages));
*R(VIRTIO_MMIO_QUEUE_PFN) = ((uint64)pages) >> PGSHIFT; *R(VIRTIO_MMIO_QUEUE_PFN) = ((uint64)disk.pages) >> PGSHIFT;
// desc = pages -- num * VRingDesc // desc = pages -- num * VRingDesc
// avail = pages + 0x40 -- 2 * uint16, then num * uint16 // avail = pages + 0x40 -- 2 * uint16, then num * uint16
// used = pages + 4096 -- 2 * uint16, then num * vRingUsedElem // used = pages + 4096 -- 2 * uint16, then num * vRingUsedElem
desc = (struct VRingDesc *) pages; disk.desc = (struct VRingDesc *) disk.pages;
avail = (uint16*)(((char*)desc) + NUM*sizeof(struct VRingDesc)); disk.avail = (uint16*)(((char*)disk.desc) + NUM*sizeof(struct VRingDesc));
used = (struct UsedArea *) (pages + PGSIZE); disk.used = (struct UsedArea *) (disk.pages + PGSIZE);
for(int i = 0; i < NUM; i++) for(int i = 0; i < NUM; i++)
free[i] = 1; disk.free[i] = 1;
// plic.c and trap.c arrange for interrupts from VIRTIO0_IRQ. // plic.c and trap.c arrange for interrupts from VIRTIO0_IRQ.
} }
@ -115,8 +117,8 @@ static int
alloc_desc() alloc_desc()
{ {
for(int i = 0; i < NUM; i++){ for(int i = 0; i < NUM; i++){
if(free[i]){ if(disk.free[i]){
free[i] = 0; disk.free[i] = 0;
return i; return i;
} }
} }
@ -129,11 +131,11 @@ free_desc(int i)
{ {
if(i >= NUM) if(i >= NUM)
panic("virtio_disk_intr 1"); panic("virtio_disk_intr 1");
if(free[i]) if(disk.free[i])
panic("virtio_disk_intr 2"); panic("virtio_disk_intr 2");
desc[i].addr = 0; disk.desc[i].addr = 0;
free[i] = 1; disk.free[i] = 1;
wakeup(&free[0]); wakeup(&disk.free[0]);
} }
// free a chain of descriptors. // free a chain of descriptors.
@ -142,8 +144,8 @@ free_chain(int i)
{ {
while(1){ while(1){
free_desc(i); free_desc(i);
if(desc[i].flags & VRING_DESC_F_NEXT) if(disk.desc[i].flags & VRING_DESC_F_NEXT)
i = desc[i].next; i = disk.desc[i].next;
else else
break; break;
} }
@ -168,7 +170,7 @@ virtio_disk_rw(struct buf *b, int write)
{ {
uint64 sector = b->blockno * (BSIZE / 512); uint64 sector = b->blockno * (BSIZE / 512);
acquire(&vdisk_lock); acquire(&disk.vdisk_lock);
// the spec says that legacy block operations use three // the spec says that legacy block operations use three
// descriptors: one for type/reserved/sector, one for // descriptors: one for type/reserved/sector, one for
@ -180,7 +182,7 @@ virtio_disk_rw(struct buf *b, int write)
if(alloc3_desc(idx) == 0) { if(alloc3_desc(idx) == 0) {
break; break;
} }
sleep(&free[0], &vdisk_lock); sleep(&disk.free[0], &disk.vdisk_lock);
} }
// format the three descriptors. // format the three descriptors.
@ -201,67 +203,67 @@ virtio_disk_rw(struct buf *b, int write)
// buf0 is on a kernel stack, which is not direct mapped, // buf0 is on a kernel stack, which is not direct mapped,
// thus the call to kvmpa(). // thus the call to kvmpa().
desc[idx[0]].addr = (uint64) kvmpa((uint64) &buf0); disk.desc[idx[0]].addr = (uint64) kvmpa((uint64) &buf0);
desc[idx[0]].len = sizeof(buf0); disk.desc[idx[0]].len = sizeof(buf0);
desc[idx[0]].flags = VRING_DESC_F_NEXT; disk.desc[idx[0]].flags = VRING_DESC_F_NEXT;
desc[idx[0]].next = idx[1]; disk.desc[idx[0]].next = idx[1];
desc[idx[1]].addr = (uint64) b->data; disk.desc[idx[1]].addr = (uint64) b->data;
desc[idx[1]].len = BSIZE; disk.desc[idx[1]].len = BSIZE;
if(write) if(write)
desc[idx[1]].flags = 0; // device reads b->data disk.desc[idx[1]].flags = 0; // device reads b->data
else else
desc[idx[1]].flags = VRING_DESC_F_WRITE; // device writes b->data disk.desc[idx[1]].flags = VRING_DESC_F_WRITE; // device writes b->data
desc[idx[1]].flags |= VRING_DESC_F_NEXT; disk.desc[idx[1]].flags |= VRING_DESC_F_NEXT;
desc[idx[1]].next = idx[2]; disk.desc[idx[1]].next = idx[2];
info[idx[0]].status = 0; disk.info[idx[0]].status = 0;
desc[idx[2]].addr = (uint64) &info[idx[0]].status; disk.desc[idx[2]].addr = (uint64) &disk.info[idx[0]].status;
desc[idx[2]].len = 1; disk.desc[idx[2]].len = 1;
desc[idx[2]].flags = VRING_DESC_F_WRITE; // device writes the status disk.desc[idx[2]].flags = VRING_DESC_F_WRITE; // device writes the status
desc[idx[2]].next = 0; disk.desc[idx[2]].next = 0;
// record struct buf for virtio_disk_intr(). // record struct buf for virtio_disk_intr().
b->disk = 1; b->disk = 1;
info[idx[0]].b = b; disk.info[idx[0]].b = b;
// avail[0] is flags // avail[0] is flags
// avail[1] tells the device how far to look in avail[2...]. // avail[1] tells the device how far to look in avail[2...].
// avail[2...] are desc[] indices the device should process. // avail[2...] are desc[] indices the device should process.
// we only tell device the first index in our chain of descriptors. // we only tell device the first index in our chain of descriptors.
avail[2 + (avail[1] % NUM)] = idx[0]; disk.avail[2 + (disk.avail[1] % NUM)] = idx[0];
__sync_synchronize(); __sync_synchronize();
avail[1] = avail[1] + 1; disk.avail[1] = disk.avail[1] + 1;
*R(VIRTIO_MMIO_QUEUE_NOTIFY) = 0; // value is queue number *R(VIRTIO_MMIO_QUEUE_NOTIFY) = 0; // value is queue number
// Wait for virtio_disk_intr() to say request has finished. // Wait for virtio_disk_intr() to say request has finished.
while(b->disk == 1) { while(b->disk == 1) {
sleep(b, &vdisk_lock); sleep(b, &disk.vdisk_lock);
} }
info[idx[0]].b = 0; disk.info[idx[0]].b = 0;
free_chain(idx[0]); free_chain(idx[0]);
release(&vdisk_lock); release(&disk.vdisk_lock);
} }
void void
virtio_disk_intr() virtio_disk_intr()
{ {
acquire(&vdisk_lock); acquire(&disk.vdisk_lock);
while((used_idx % NUM) != (used->id % NUM)){ while((disk.used_idx % NUM) != (disk.used->id % NUM)){
int id = used->elems[used_idx].id; int id = disk.used->elems[disk.used_idx].id;
if(info[id].status != 0) if(disk.info[id].status != 0)
panic("virtio_disk_intr status"); panic("virtio_disk_intr status");
info[id].b->disk = 0; // disk is done with buf disk.info[id].b->disk = 0; // disk is done with buf
wakeup(info[id].b); wakeup(disk.info[id].b);
used_idx = (used_idx + 1) % NUM; disk.used_idx = (disk.used_idx + 1) % NUM;
} }
release(&vdisk_lock); release(&disk.vdisk_lock);
} }