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dataplane: use the QEMU block layer for I/O 

Stop using a custom Linux AIO request queue from ioq.h and instead use
the QEMU block layer for I/O.

This patch adjusts the VirtIOBlockRequest struct with fields needed for
bdrv_aio_readv()/bdrv_aio_writev().  ioq.h used struct iovec and struct
iocb, which we don't need directly anymore.

Modify dataplane start/stop to set the AioContext on the
BlockDriverState.  We also no longer need to get the raw-posix file
descriptor.  This means image formats are now supported with dataplane!

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2014-05-08 16:34:55 +02:00
parent c75f3bdf46
commit 580b6b2aa2
1 changed files with 63 additions and 126 deletions
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189
hw/block/dataplane/virtio-blk.c
View File

@ -17,7 +17,6 @@
#include "qemu/thread.h"
#include "qemu/error-report.h"
#include "hw/virtio/dataplane/vring.h"
#include "ioq.h"
#include "block/block.h"
#include "hw/virtio/virtio-blk.h"
#include "virtio-blk.h"
@ -25,20 +24,14 @@
#include "hw/virtio/virtio-bus.h"
#include "qom/object_interfaces.h"
enum {
SEG_MAX = 126, /* maximum number of I/O segments */
VRING_MAX = SEG_MAX + 2, /* maximum number of vring descriptors */
REQ_MAX = VRING_MAX, /* maximum number of requests in the vring,
* is VRING_MAX / 2 with traditional and
* VRING_MAX with indirect descriptors */
};
typedef struct {
struct iocb iocb; /* Linux AIO control block */
VirtIOBlockDataPlane *s;
QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
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 */
QEMUIOVector qiov; /* original request iovecs */
struct iovec bounce_iov; /* used if guest buffers are unaligned */
QEMUIOVector bounce_qiov; /* bounce buffer iovecs */
bool read; /* read or write? */
} VirtIOBlockRequest;
struct VirtIOBlockDataPlane {
@ -61,16 +54,8 @@ struct VirtIOBlockDataPlane {
IOThread *iothread;
IOThread internal_iothread_obj;
AioContext *ctx;
EventNotifier io_notifier; /* Linux AIO completion */
EventNotifier host_notifier; /* doorbell */
IOQueue ioqueue; /* Linux AIO queue (should really be per
IOThread) */
VirtIOBlockRequest requests[REQ_MAX]; /* pool of requests, managed by the
queue */
unsigned int num_reqs;
/* Operation blocker on BDS */
Error *blocker;
};
@ -85,33 +70,28 @@ static void notify_guest(VirtIOBlockDataPlane *s)
event_notifier_set(s->guest_notifier);
}
static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
static void complete_rdwr(void *opaque, int ret)
{
VirtIOBlockDataPlane *s = opaque;
VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
VirtIOBlockRequest *req = opaque;
struct virtio_blk_inhdr hdr;
int len;
if (likely(ret >= 0)) {
if (likely(ret == 0)) {
hdr.status = VIRTIO_BLK_S_OK;
len = ret;
len = req->qiov.size;
} else {
hdr.status = VIRTIO_BLK_S_IOERR;
len = 0;
}
trace_virtio_blk_data_plane_complete_request(s, req->elem->index, ret);
trace_virtio_blk_data_plane_complete_request(req->s, req->elem->index, ret);
if (req->read_qiov) {
assert(req->bounce_iov);
qemu_iovec_from_buf(req->read_qiov, 0, req->bounce_iov->iov_base, len);
qemu_iovec_destroy(req->read_qiov);
g_slice_free(QEMUIOVector, req->read_qiov);
if (req->read && req->bounce_iov.iov_base) {
qemu_iovec_from_buf(&req->qiov, 0, req->bounce_iov.iov_base, len);
}
if (req->bounce_iov) {
qemu_vfree(req->bounce_iov->iov_base);
g_slice_free(struct iovec, req->bounce_iov);
if (req->bounce_iov.iov_base) {
qemu_vfree(req->bounce_iov.iov_base);
}
qemu_iovec_from_buf(req->inhdr, 0, &hdr, sizeof(hdr));
@ -122,9 +102,9 @@ 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->elem, len + sizeof(hdr));
req->elem = NULL;
s->num_reqs--;
vring_push(&req->s->vring, req->elem, len + sizeof(hdr));
notify_guest(req->s);
g_slice_free(VirtIOBlockRequest, req);
}
static void complete_request_early(VirtIOBlockDataPlane *s, VirtQueueElement *elem,
@ -155,51 +135,52 @@ static void do_get_id_cmd(VirtIOBlockDataPlane *s,
complete_request_early(s, elem, inhdr, VIRTIO_BLK_S_OK);
}
static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
struct iovec *iov, unsigned iov_cnt,
long long offset, VirtQueueElement *elem,
QEMUIOVector *inhdr)
static void do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
struct iovec *iov, unsigned iov_cnt,
int64_t sector_num, VirtQueueElement *elem,
QEMUIOVector *inhdr)
{
struct iocb *iocb;
QEMUIOVector qiov;
struct iovec *bounce_iov = NULL;
QEMUIOVector *read_qiov = NULL;
VirtIOBlockRequest *req = g_slice_new0(VirtIOBlockRequest);
QEMUIOVector *qiov;
int nb_sectors;
qemu_iovec_init_external(&qiov, iov, iov_cnt);
if (!bdrv_qiov_is_aligned(s->blk->conf.bs, &qiov)) {
void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov.size);
/* Fill in virtio block metadata needed for completion */
req->s = s;
req->elem = elem;
req->inhdr = inhdr;
req->read = read;
qemu_iovec_init_external(&req->qiov, iov, iov_cnt);
if (read) {
/* Need to copy back from bounce buffer on completion */
read_qiov = g_slice_new(QEMUIOVector);
qemu_iovec_init(read_qiov, iov_cnt);
qemu_iovec_concat_iov(read_qiov, iov, iov_cnt, 0, qiov.size);
} else {
qemu_iovec_to_buf(&qiov, 0, bounce_buffer, qiov.size);
qiov = &req->qiov;
if (!bdrv_qiov_is_aligned(s->blk->conf.bs, qiov)) {
void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov->size);
/* Populate bounce buffer with data for writes */
if (!read) {
qemu_iovec_to_buf(qiov, 0, bounce_buffer, qiov->size);
}
/* Redirect I/O to aligned bounce buffer */
bounce_iov = g_slice_new(struct iovec);
bounce_iov->iov_base = bounce_buffer;
bounce_iov->iov_len = qiov.size;
iov = bounce_iov;
iov_cnt = 1;
req->bounce_iov.iov_base = bounce_buffer;
req->bounce_iov.iov_len = qiov->size;
qemu_iovec_init_external(&req->bounce_qiov, &req->bounce_iov, 1);
qiov = &req->bounce_qiov;
}
iocb = ioq_rdwr(&s->ioqueue, read, iov, iov_cnt, offset);
nb_sectors = qiov->size / BDRV_SECTOR_SIZE;
/* Fill in virtio block metadata needed for completion */
VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
req->elem = elem;
req->inhdr = inhdr;
req->bounce_iov = bounce_iov;
req->read_qiov = read_qiov;
return 0;
if (read) {
bdrv_aio_readv(s->blk->conf.bs, sector_num, qiov, nb_sectors,
complete_rdwr, req);
} else {
bdrv_aio_writev(s->blk->conf.bs, sector_num, qiov, nb_sectors,
complete_rdwr, req);
}
}
static int process_request(IOQueue *ioq, VirtQueueElement *elem)
static int process_request(VirtIOBlockDataPlane *s, VirtQueueElement *elem)
{
VirtIOBlockDataPlane *s = container_of(ioq, VirtIOBlockDataPlane, ioqueue);
struct iovec *iov = elem->out_sg;
struct iovec *in_iov = elem->in_sg;
unsigned out_num = elem->out_num;
@ -234,11 +215,15 @@ static int process_request(IOQueue *ioq, VirtQueueElement *elem)
switch (outhdr.type) {
case VIRTIO_BLK_T_IN:
do_rdwr_cmd(s, true, in_iov, in_num, outhdr.sector * 512, elem, inhdr);
do_rdwr_cmd(s, true, in_iov, in_num,
outhdr.sector * 512 / BDRV_SECTOR_SIZE,
elem, inhdr);
return 0;
case VIRTIO_BLK_T_OUT:
do_rdwr_cmd(s, false, iov, out_num, outhdr.sector * 512, elem, inhdr);
do_rdwr_cmd(s, false, iov, out_num,
outhdr.sector * 512 / BDRV_SECTOR_SIZE,
elem, inhdr);
return 0;
case VIRTIO_BLK_T_SCSI_CMD:
@ -274,7 +259,6 @@ static void handle_notify(EventNotifier *e)
VirtQueueElement *elem;
int ret;
unsigned int num_queued;
event_notifier_test_and_clear(&s->host_notifier);
for (;;) {
@ -291,7 +275,7 @@ static void handle_notify(EventNotifier *e)
trace_virtio_blk_data_plane_process_request(s, elem->out_num,
elem->in_num, elem->index);
if (process_request(&s->ioqueue, elem) < 0) {
if (process_request(s, elem) < 0) {
vring_set_broken(&s->vring);
vring_free_element(elem);
ret = -EFAULT;
@ -306,44 +290,10 @@ static void handle_notify(EventNotifier *e)
if (vring_enable_notification(s->vdev, &s->vring)) {
break;
}
} 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.
*/
} else { /* fatal error */
break;
}
}
num_queued = ioq_num_queued(&s->ioqueue);
if (num_queued > 0) {
s->num_reqs += num_queued;
int rc = ioq_submit(&s->ioqueue);
if (unlikely(rc < 0)) {
fprintf(stderr, "ioq_submit failed %d\n", rc);
exit(1);
}
}
}
static void handle_io(EventNotifier *e)
{
VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
io_notifier);
event_notifier_test_and_clear(&s->io_notifier);
if (ioq_run_completion(&s->ioqueue, complete_request, s) > 0) {
notify_guest(s);
}
/* If there were more requests than iovecs, the vring will not be empty yet
* so check again. There should now be enough resources to process more
* requests.
*/
if (unlikely(vring_more_avail(&s->vring))) {
handle_notify(&s->host_notifier);
}
}
/* Context: QEMU global mutex held */
@ -437,7 +387,6 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
VirtQueue *vq;
int i;
if (s->started) {
return;
@ -470,24 +419,18 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
}
s->host_notifier = *virtio_queue_get_host_notifier(vq);
/* Set up ioqueue */
ioq_init(&s->ioqueue, s->fd, REQ_MAX);
for (i = 0; i < ARRAY_SIZE(s->requests); i++) {
ioq_put_iocb(&s->ioqueue, &s->requests[i].iocb);
}
s->io_notifier = *ioq_get_notifier(&s->ioqueue);
s->starting = false;
s->started = true;
trace_virtio_blk_data_plane_start(s);
bdrv_set_aio_context(s->blk->conf.bs, s->ctx);
/* Kick right away to begin processing requests already in vring */
event_notifier_set(virtio_queue_get_host_notifier(vq));
/* Get this show started by hooking up our callbacks */
aio_context_acquire(s->ctx);
aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify);
aio_set_event_notifier(s->ctx, &s->io_notifier, handle_io);
aio_context_release(s->ctx);
}
@ -507,13 +450,8 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
/* Stop notifications for new requests from guest */
aio_set_event_notifier(s->ctx, &s->host_notifier, NULL);
/* Complete pending requests */
while (s->num_reqs > 0) {
aio_poll(s->ctx, true);
}
/* Stop ioq callbacks (there are no pending requests left) */
aio_set_event_notifier(s->ctx, &s->io_notifier, NULL);
/* Drain and switch bs back to the QEMU main loop */
bdrv_set_aio_context(s->blk->conf.bs, qemu_get_aio_context());
aio_context_release(s->ctx);
@ -522,7 +460,6 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
*/
vring_teardown(&s->vring, s->vdev, 0);
ioq_cleanup(&s->ioqueue);
k->set_host_notifier(qbus->parent, 0, false);
/* Clean up guest notifier (irq) */