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dataplane: change vring API to use VirtQueueElement

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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-12-10 13:27:00 +01:00 • committed by Stefan Hajnoczi
parent 781c117f37
commit 8c1b566fd1
3 changed files with 72 additions and 76 deletions
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85
hw/block/dataplane/virtio-blk.c
View file

@ -35,7 +35,7 @@ enum {
typedef struct {
struct iocb iocb; /* Linux AIO control block */
QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
unsigned int head; /* vring descriptor index */
VirtQueueElement *elem; /* saved data from the virtqueue */
struct iovec *bounce_iov; /* used if guest buffers are unaligned */
QEMUIOVector *read_qiov; /* for read completion /w bounce buffer */
} VirtIOBlockRequest;
@ -96,7 +96,7 @@ static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
len = 0;
}
trace_virtio_blk_data_plane_complete_request(s, req->head, ret);
trace_virtio_blk_data_plane_complete_request(s, req->elem->index, ret);
if (req->read_qiov) {
assert(req->bounce_iov);
@ -118,12 +118,12 @@ static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
* written to, but for virtio-blk it seems to be the number of bytes
* transferred plus the status bytes.
*/
vring_push(&s->vring, req->head, len + sizeof(hdr));
vring_push(&s->vring, req->elem, len + sizeof(hdr));
req->elem = NULL;
s->num_reqs--;
}
static void complete_request_early(VirtIOBlockDataPlane *s, unsigned int head,
static void complete_request_early(VirtIOBlockDataPlane *s, VirtQueueElement *elem,
QEMUIOVector *inhdr, unsigned char status)
{
struct virtio_blk_inhdr hdr = {
@ -134,26 +134,26 @@ static void complete_request_early(VirtIOBlockDataPlane *s, unsigned int head,
qemu_iovec_destroy(inhdr);
g_slice_free(QEMUIOVector, inhdr);
vring_push(&s->vring, head, sizeof(hdr));
vring_push(&s->vring, elem, sizeof(hdr));
notify_guest(s);
}
/* Get disk serial number */
static void do_get_id_cmd(VirtIOBlockDataPlane *s,
struct iovec *iov, unsigned int iov_cnt,
unsigned int head, QEMUIOVector *inhdr)
VirtQueueElement *elem, QEMUIOVector *inhdr)
{
char id[VIRTIO_BLK_ID_BYTES];
/* Serial number not NUL-terminated when shorter than buffer */
strncpy(id, s->blk->serial ? s->blk->serial : "", sizeof(id));
iov_from_buf(iov, iov_cnt, 0, id, sizeof(id));
complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
complete_request_early(s, elem, inhdr, VIRTIO_BLK_S_OK);
}
static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
struct iovec *iov, unsigned int iov_cnt,
long long offset, unsigned int head,
struct iovec *iov, unsigned iov_cnt,
long long offset, VirtQueueElement *elem,
QEMUIOVector *inhdr)
{
struct iocb *iocb;
@ -186,19 +186,20 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
/* Fill in virtio block metadata needed for completion */
VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
req->head = head;
req->elem = elem;
req->inhdr = inhdr;
req->bounce_iov = bounce_iov;
req->read_qiov = read_qiov;
return 0;
}
static int process_request(IOQueue *ioq, struct iovec iov[],
unsigned int out_num, unsigned int in_num,
unsigned int head)
static int process_request(IOQueue *ioq, VirtQueueElement *elem)
{
VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
struct iovec *in_iov = &iov[out_num];
struct iovec *iov = elem->out_sg;
struct iovec *in_iov = elem->in_sg;
unsigned out_num = elem->out_num;
unsigned in_num = elem->in_num;
struct virtio_blk_outhdr outhdr;
QEMUIOVector *inhdr;
size_t in_size;
@ -229,29 +230,29 @@ static int process_request(IOQueue *ioq, struct iovec iov[],
switch (outhdr.type) {
case VIRTIO_BLK_T_IN:
do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, head, inhdr);
do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, elem, inhdr);
return 0;
case VIRTIO_BLK_T_OUT:
do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, head, inhdr);
do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, elem, inhdr);
return 0;
case VIRTIO_BLK_T_SCSI_CMD:
/* TODO support SCSI commands */
complete_request_early(s, head, inhdr, VIRTIO_BLK_S_UNSUPP);
complete_request_early(s, elem, inhdr, VIRTIO_BLK_S_UNSUPP);
return 0;
case VIRTIO_BLK_T_FLUSH:
/* TODO fdsync not supported by Linux AIO, do it synchronously here! */
if (qemu_fdatasync(s->fd) < 0) {
complete_request_early(s, head, inhdr, VIRTIO_BLK_S_IOERR);
complete_request_early(s, elem, inhdr, VIRTIO_BLK_S_IOERR);
} else {
complete_request_early(s, head, inhdr, VIRTIO_BLK_S_OK);
complete_request_early(s, elem, inhdr, VIRTIO_BLK_S_OK);
}
return 0;
case VIRTIO_BLK_T_GET_ID:
do_get_id_cmd(s, in_iov, in_num, head, inhdr);
do_get_id_cmd(s, in_iov, in_num, elem, inhdr);
return 0;
default:
@ -267,29 +268,8 @@ static void handle_notify(EventNotifier *e)
VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
host_notifier);
/* There is one array of iovecs into which all new requests are extracted
* from the vring. Requests are read from the vring and the translated
* descriptors are written to the iovecs array. The iovecs do not have to
* persist across handle_notify() calls because the kernel copies the
* iovecs on io_submit().
*
* Handling io_submit() EAGAIN may require storing the requests across
* handle_notify() calls until the kernel has sufficient resources to
* accept more I/O. This is not implemented yet.
*/
struct iovec iovec[VRING_MAX];
struct iovec *end = &iovec[VRING_MAX];
struct iovec *iov = iovec;
/* When a request is read from the vring, the index of the first descriptor
* (aka head) is returned so that the completed request can be pushed onto
* the vring later.
*
* The number of hypervisor read-only iovecs is out_num. The number of
* hypervisor write-only iovecs is in_num.
*/
int head;
unsigned int out_num = 0, in_num = 0;
VirtQueueElement *elem;
int ret;
unsigned int num_queued;
event_notifier_test_and_clear(&s->host_notifier);
@ -298,30 +278,31 @@ static void handle_notify(EventNotifier *e)
vring_disable_notification(s->vdev, &s->vring);
for (;;) {
head = vring_pop(s->vdev, &s->vring, iov, end, &out_num, &in_num);
if (head < 0) {
ret = vring_pop(s->vdev, &s->vring, &elem);
if (ret < 0) {
assert(elem == NULL);
break; /* no more requests */
}
trace_virtio_blk_data_plane_process_request(s, out_num, in_num,
head);
trace_virtio_blk_data_plane_process_request(s, elem->out_num,
elem->in_num, elem->index);
if (process_request(&s->ioqueue, iov, out_num, in_num, head) < 0) {
if (process_request(&s->ioqueue, elem) < 0) {
vring_set_broken(&s->vring);
vring_free_element(elem);
ret = -EFAULT;
break;
}
iov += out_num + in_num;
}
if (likely(head == -EAGAIN)) { /* vring emptied */
if (likely(ret == -EAGAIN)) { /* vring emptied */
/* Re-enable guest->host notifies and stop processing the vring.
* But if the guest has snuck in more descriptors, keep processing.
*/
if (vring_enable_notification(s->vdev, &s->vring)) {
break;
}
} else { /* head == -ENOBUFS or fatal error, iovecs[] is depleted */
} else { /* ret == -ENOBUFS or fatal error, iovecs[] is depleted */
/* Since there are no iovecs[] left, stop processing for now. Do
* not re-enable guest->host notifies since the I/O completion
* handler knows to check for more vring descriptors anyway.