274 lines
6.9 KiB
C
274 lines
6.9 KiB
C
//
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// driver for qemu's virtio disk device.
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// uses qemu's mmio interface to virtio.
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// qemu presents a "legacy" virtio interface.
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//
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// qemu ... -drive file=fs.img,if=none,format=raw,id=x0 -device virtio-blk-device,drive=x0,bus=virtio-mmio-bus.0
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//
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#include "include/types.h"
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#include "include/riscv.h"
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#include "include/defs.h"
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#include "include/param.h"
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#include "include/memlayout.h"
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#include "include/spinlock.h"
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#include "include/sleeplock.h"
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#include "include/fs.h"
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#include "include/buf.h"
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#include "include/virtio.h"
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// the address of virtio mmio register r.
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#define R(r) ((volatile uint32 *)(VIRTIO0 + (r)))
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static struct disk {
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// memory for virtio descriptors &c for queue 0.
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// this is a global instead of allocated because it must
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// be multiple contiguous pages, which kalloc()
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// doesn't support, and page aligned.
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char pages[2*PGSIZE];
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struct VRingDesc *desc;
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uint16 *avail;
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struct UsedArea *used;
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// our own book-keeping.
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char free[NUM]; // is a descriptor free?
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uint16 used_idx; // we've looked this far in used[2..NUM].
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// track info about in-flight operations,
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// for use when completion interrupt arrives.
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// indexed by first descriptor index of chain.
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struct {
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struct buf *b;
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char status;
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} info[NUM];
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struct spinlock vdisk_lock;
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} __attribute__ ((aligned (PGSIZE))) disk;
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void
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virtio_disk_init(void)
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{
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uint32 status = 0;
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initlock(&disk.vdisk_lock, "virtio_disk");
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if(*R(VIRTIO_MMIO_MAGIC_VALUE) != 0x74726976 ||
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*R(VIRTIO_MMIO_VERSION) != 1 ||
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*R(VIRTIO_MMIO_DEVICE_ID) != 2 ||
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*R(VIRTIO_MMIO_VENDOR_ID) != 0x554d4551){
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panic("could not find virtio disk");
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}
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status |= VIRTIO_CONFIG_S_ACKNOWLEDGE;
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*R(VIRTIO_MMIO_STATUS) = status;
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status |= VIRTIO_CONFIG_S_DRIVER;
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*R(VIRTIO_MMIO_STATUS) = status;
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// negotiate features
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uint64 features = *R(VIRTIO_MMIO_DEVICE_FEATURES);
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features &= ~(1 << VIRTIO_BLK_F_RO);
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features &= ~(1 << VIRTIO_BLK_F_SCSI);
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features &= ~(1 << VIRTIO_BLK_F_CONFIG_WCE);
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features &= ~(1 << VIRTIO_BLK_F_MQ);
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features &= ~(1 << VIRTIO_F_ANY_LAYOUT);
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features &= ~(1 << VIRTIO_RING_F_EVENT_IDX);
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features &= ~(1 << VIRTIO_RING_F_INDIRECT_DESC);
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*R(VIRTIO_MMIO_DRIVER_FEATURES) = features;
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// tell device that feature negotiation is complete.
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status |= VIRTIO_CONFIG_S_FEATURES_OK;
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*R(VIRTIO_MMIO_STATUS) = status;
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// tell device we're completely ready.
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status |= VIRTIO_CONFIG_S_DRIVER_OK;
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*R(VIRTIO_MMIO_STATUS) = status;
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*R(VIRTIO_MMIO_GUEST_PAGE_SIZE) = PGSIZE;
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// initialize queue 0.
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*R(VIRTIO_MMIO_QUEUE_SEL) = 0;
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uint32 max = *R(VIRTIO_MMIO_QUEUE_NUM_MAX);
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if(max == 0)
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panic("virtio disk has no queue 0");
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if(max < NUM)
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panic("virtio disk max queue too short");
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*R(VIRTIO_MMIO_QUEUE_NUM) = NUM;
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memset(disk.pages, 0, sizeof(disk.pages));
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*R(VIRTIO_MMIO_QUEUE_PFN) = ((uint64)disk.pages) >> PGSHIFT;
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// desc = pages -- num * VRingDesc
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// avail = pages + 0x40 -- 2 * uint16, then num * uint16
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// used = pages + 4096 -- 2 * uint16, then num * vRingUsedElem
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disk.desc = (struct VRingDesc *) disk.pages;
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disk.avail = (uint16*)(((char*)disk.desc) + NUM*sizeof(struct VRingDesc));
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disk.used = (struct UsedArea *) (disk.pages + PGSIZE);
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for(int i = 0; i < NUM; i++)
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disk.free[i] = 1;
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// plic.c and trap.c arrange for interrupts from VIRTIO0_IRQ.
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printf("virtio_disk_init\n");
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}
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// find a free descriptor, mark it non-free, return its index.
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static int
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alloc_desc()
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{
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for(int i = 0; i < NUM; i++){
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if(disk.free[i]){
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disk.free[i] = 0;
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return i;
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}
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}
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return -1;
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}
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// mark a descriptor as free.
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static void
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free_desc(int i)
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{
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if(i >= NUM)
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panic("virtio_disk_intr 1");
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if(disk.free[i])
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panic("virtio_disk_intr 2");
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disk.desc[i].addr = 0;
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disk.free[i] = 1;
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wakeup(&disk.free[0]);
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}
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// free a chain of descriptors.
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static void
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free_chain(int i)
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{
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while(1){
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free_desc(i);
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if(disk.desc[i].flags & VRING_DESC_F_NEXT)
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i = disk.desc[i].next;
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else
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break;
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}
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}
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static int
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alloc3_desc(int *idx)
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{
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for(int i = 0; i < 3; i++){
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idx[i] = alloc_desc();
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if(idx[i] < 0){
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for(int j = 0; j < i; j++)
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free_desc(idx[j]);
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return -1;
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}
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}
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return 0;
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}
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void
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virtio_disk_rw(struct buf *b, int write)
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{
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uint64 sector = b->blockno * (BSIZE / 512);
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acquire(&disk.vdisk_lock);
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// the spec says that legacy block operations use three
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// descriptors: one for type/reserved/sector, one for
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// the data, one for a 1-byte status result.
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// allocate the three descriptors.
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int idx[3];
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while(1){
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if(alloc3_desc(idx) == 0) {
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break;
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}
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sleep(&disk.free[0], &disk.vdisk_lock);
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}
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// format the three descriptors.
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// qemu's virtio-blk.c reads them.
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struct virtio_blk_outhdr {
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uint32 type;
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uint32 reserved;
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uint64 sector;
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} buf0;
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if(write)
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buf0.type = VIRTIO_BLK_T_OUT; // write the disk
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else
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buf0.type = VIRTIO_BLK_T_IN; // read the disk
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buf0.reserved = 0;
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buf0.sector = sector;
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// buf0 is on a kernel stack, which is not direct mapped,
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// thus the call to kvmpa().
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disk.desc[idx[0]].addr = (uint64) kvmpa((uint64) &buf0);
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disk.desc[idx[0]].len = sizeof(buf0);
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disk.desc[idx[0]].flags = VRING_DESC_F_NEXT;
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disk.desc[idx[0]].next = idx[1];
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disk.desc[idx[1]].addr = (uint64) b->data;
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disk.desc[idx[1]].len = BSIZE;
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if(write)
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disk.desc[idx[1]].flags = 0; // device reads b->data
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else
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disk.desc[idx[1]].flags = VRING_DESC_F_WRITE; // device writes b->data
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disk.desc[idx[1]].flags |= VRING_DESC_F_NEXT;
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disk.desc[idx[1]].next = idx[2];
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disk.info[idx[0]].status = 0;
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disk.desc[idx[2]].addr = (uint64) &disk.info[idx[0]].status;
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disk.desc[idx[2]].len = 1;
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disk.desc[idx[2]].flags = VRING_DESC_F_WRITE; // device writes the status
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disk.desc[idx[2]].next = 0;
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// record struct buf for virtio_disk_intr().
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b->disk = 1;
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disk.info[idx[0]].b = b;
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// avail[0] is flags
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// avail[1] tells the device how far to look in avail[2...].
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// avail[2...] are desc[] indices the device should process.
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// we only tell device the first index in our chain of descriptors.
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disk.avail[2 + (disk.avail[1] % NUM)] = idx[0];
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__sync_synchronize();
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disk.avail[1] = disk.avail[1] + 1;
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*R(VIRTIO_MMIO_QUEUE_NOTIFY) = 0; // value is queue number
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// Wait for virtio_disk_intr() to say request has finished.
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while(b->disk == 1) {
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sleep(b, &disk.vdisk_lock);
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}
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disk.info[idx[0]].b = 0;
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free_chain(idx[0]);
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release(&disk.vdisk_lock);
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}
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void
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virtio_disk_intr()
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{
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acquire(&disk.vdisk_lock);
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while((disk.used_idx % NUM) != (disk.used->id % NUM)){
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int id = disk.used->elems[disk.used_idx].id;
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if(disk.info[id].status != 0)
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panic("virtio_disk_intr status");
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disk.info[id].b->disk = 0; // disk is done with buf
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wakeup(disk.info[id].b);
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disk.used_idx = (disk.used_idx + 1) % NUM;
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}
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*R(VIRTIO_MMIO_INTERRUPT_ACK) = *R(VIRTIO_MMIO_INTERRUPT_STATUS) & 0x3;
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release(&disk.vdisk_lock);
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}
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