Imbus/xv6-riscv-kernel
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clean up virtio code

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This commit is contained in:
Robert Morris 2019-06-13 09:40:17 -04:00
parent 4adf016925
commit ca39672a30
6 changed files with 46 additions and 39 deletions
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64
kernel/virtio_disk.c
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@ -17,8 +17,8 @@
#include "buf.h"
#include "virtio.h"
// the address of a virtio mmio register.
#define R(off) ((volatile uint32 *)(VIRTIO + (off)))
// the address of virtio mmio register r.
#define R(r) ((volatile uint32 *)(VIRTIO0 + (r)))
struct spinlock virtio_disk_lock;
@ -45,6 +45,7 @@ static uint16 used_idx; // we've looked this far in used[2..NUM].
// indexed by first descriptor index of chain.
static struct {
struct buf *b;
char status;
} info[NUM];
void
@ -54,8 +55,6 @@ virtio_disk_init(void)
initlock(&virtio_disk_lock, "virtio_disk");
// qemu's virtio-mmio.c
if(*R(VIRTIO_MMIO_MAGIC_VALUE) != 0x74726976 ||
*R(VIRTIO_MMIO_VERSION) != 1 ||
*R(VIRTIO_MMIO_DEVICE_ID) != 2 ||
@ -90,9 +89,7 @@ virtio_disk_init(void)
*R(VIRTIO_MMIO_GUEST_PAGE_SIZE) = PGSIZE;
// qemu's hw/virtio/virtio.c
// initialize queue 0
// initialize queue 0.
*R(VIRTIO_MMIO_QUEUE_SEL) = 0;
uint32 max = *R(VIRTIO_MMIO_QUEUE_NUM_MAX);
if(max == 0)
@ -113,6 +110,8 @@ virtio_disk_init(void)
for(int i = 0; i < NUM; i++)
free[i] = 1;
// plic.c and trap.c arrange for interrupts from VIRTIO0_IRQ.
}
// find a free descriptor, mark it non-free, return its index.
@ -128,14 +127,30 @@ alloc_desc()
return -1;
}
void
// mark a descriptor as free.
static void
free_desc(int i)
{
if(i >= NUM)
panic("virtio_disk_intr 1");
if(free[i])
panic("virtio_disk_intr 2");
desc[i].addr = 0;
free[i] = 1;
wakeup(&free[0]);
}
// free a chain of descriptors.
static void
free_chain(int i)
{
while(1){
free_desc(i);
if(desc[i].flags & VRING_DESC_F_NEXT)
i = desc[i].next;
else
break;
}
}
void
@ -145,7 +160,7 @@ virtio_disk_rw(struct buf *b)
acquire(&virtio_disk_lock);
// the spec says that legacy block operations always use three
// the spec says that legacy block operations use three
// descriptors: one for type/reserved/sector, one for
// the data, one for a 1-byte status result.
@ -158,7 +173,6 @@ virtio_disk_rw(struct buf *b)
if(idx[i] < 0){
for(int j = 0; j < i; j++)
free_desc(idx[j]);
wakeup(&free[0]);
done = 0;
break;
}
@ -198,8 +212,8 @@ virtio_disk_rw(struct buf *b)
desc[idx[1]].flags |= VRING_DESC_F_NEXT;
desc[idx[1]].next = idx[2];
char status = 0;
desc[idx[2]].addr = (uint64) &status;
info[idx[0]].status = 0;
desc[idx[2]].addr = (uint64) &info[idx[0]].status;
desc[idx[2]].len = 1;
desc[idx[2]].flags = VRING_DESC_F_WRITE; // device writes the status
desc[idx[2]].next = 0;
@ -232,16 +246,16 @@ virtio_disk_intr()
// uint16 flags
// uint16 idx
// array of VRingUsedElem
// XXX spec says to read INTERRUPT_STATUS and
// write INTERRUPT_ACK
volatile uint16 *idxp = (uint16 *)(used + 2);
volatile struct VRingUsedElem *e0 = (struct VRingUsedElem *)(used + 4);
acquire(&virtio_disk_lock);
while((used_idx % NUM) != (*(volatile uint16 *)(used+2) % NUM)){
struct VRingUsedElem *ue = (struct VRingUsedElem *) (used + 4 + 8*used_idx);
// XXX check the one-byte status in the 3rd descriptor.
while((used_idx % NUM) != (*idxp % NUM)){
volatile struct VRingUsedElem *ue = &e0[used_idx];
if(info[ue->id].status != 0)
panic("virtio_disk_intr status");
info[ue->id].b->flags |= B_VALID;
info[ue->id].b->flags &= ~B_DIRTY;
@ -249,17 +263,7 @@ virtio_disk_intr()
wakeup(info[ue->id].b);
info[ue->id].b = 0;
uint i = ue->id;
while(1){
desc[i].addr = 0;
free_desc(i);
if(desc[i].flags & VRING_DESC_F_NEXT)
i = desc[i].next;
else
break;
}
wakeup(&free[0]);
free_chain(ue->id);
used_idx = (used_idx + 1) % NUM;
}