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virtio: Report real progress in VQ aio poll handler
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In virtio_queue_host_notifier_aio_poll, not all "!virtio_queue_empty()"
cases are making true progress.

Currently the offending one is virtio-scsi event queue, whose handler
does nothing if no event is pending. As a result aio_poll() will spin on
the "non-empty" VQ and take 100% host CPU.

Fix this by reporting actual progress from virtio queue aio handlers.

Reported-by: Ed Swierk <eswierk@skyportsystems.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Tested-by: Ed Swierk <eswierk@skyportsystems.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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@mstsirkin
Fam Zheng authored and mstsirkin committed Feb 17, 2017
1 parent 4bb571d commit 0793169
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Showing 8 changed files with 45 additions and 26 deletions.
4 changes: 2 additions & 2 deletions hw/block/dataplane/virtio-blk.c
View file
Expand Up @@ -147,15 +147,15 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
g_free(s);
}

static void virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
static bool virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
VirtQueue *vq)
{
VirtIOBlock *s = (VirtIOBlock *)vdev;

assert(s->dataplane);
assert(s->dataplane_started);

virtio_blk_handle_vq(s, vq);
return virtio_blk_handle_vq(s, vq);
}

/* Context: QEMU global mutex held */
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12 changes: 10 additions & 2 deletions hw/block/virtio-blk.c
View file
Expand Up @@ -581,17 +581,19 @@ static int virtio_blk_handle_request(VirtIOBlockReq *req, MultiReqBuffer *mrb)
return 0;
}

void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
bool virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
{
VirtIOBlockReq *req;
MultiReqBuffer mrb = {};
bool progress = false;

blk_io_plug(s->blk);

do {
virtio_queue_set_notification(vq, 0);

while ((req = virtio_blk_get_request(s, vq))) {
progress = true;
if (virtio_blk_handle_request(req, &mrb)) {
virtqueue_detach_element(req->vq, &req->elem, 0);
virtio_blk_free_request(req);
Expand All @@ -607,6 +609,12 @@ void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
}

blk_io_unplug(s->blk);
return progress;
}

static void virtio_blk_handle_output_do(VirtIOBlock *s, VirtQueue *vq)
{
virtio_blk_handle_vq(s, vq);
}

static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
Expand All @@ -622,7 +630,7 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
return;
}
}
virtio_blk_handle_vq(s, vq);
virtio_blk_handle_output_do(s, vq);
}

static void virtio_blk_dma_restart_bh(void *opaque)
Expand Down
14 changes: 7 additions & 7 deletions hw/scsi/virtio-scsi-dataplane.c
View file
Expand Up @@ -49,35 +49,35 @@ void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp)
}
}

static void virtio_scsi_data_plane_handle_cmd(VirtIODevice *vdev,
static bool virtio_scsi_data_plane_handle_cmd(VirtIODevice *vdev,
VirtQueue *vq)
{
VirtIOSCSI *s = (VirtIOSCSI *)vdev;

assert(s->ctx && s->dataplane_started);
virtio_scsi_handle_cmd_vq(s, vq);
return virtio_scsi_handle_cmd_vq(s, vq);
}

static void virtio_scsi_data_plane_handle_ctrl(VirtIODevice *vdev,
static bool virtio_scsi_data_plane_handle_ctrl(VirtIODevice *vdev,
VirtQueue *vq)
{
VirtIOSCSI *s = VIRTIO_SCSI(vdev);

assert(s->ctx && s->dataplane_started);
virtio_scsi_handle_ctrl_vq(s, vq);
return virtio_scsi_handle_ctrl_vq(s, vq);
}

static void virtio_scsi_data_plane_handle_event(VirtIODevice *vdev,
static bool virtio_scsi_data_plane_handle_event(VirtIODevice *vdev,
VirtQueue *vq)
{
VirtIOSCSI *s = VIRTIO_SCSI(vdev);

assert(s->ctx && s->dataplane_started);
virtio_scsi_handle_event_vq(s, vq);
return virtio_scsi_handle_event_vq(s, vq);
}

static int virtio_scsi_vring_init(VirtIOSCSI *s, VirtQueue *vq, int n,
void (*fn)(VirtIODevice *vdev, VirtQueue *vq))
VirtIOHandleAIOOutput fn)
{
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s)));
int rc;
Expand Down
14 changes: 11 additions & 3 deletions hw/scsi/virtio-scsi.c
View file
Expand Up @@ -436,13 +436,16 @@ static inline void virtio_scsi_release(VirtIOSCSI *s)
}
}

void virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq)
bool virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq)
{
VirtIOSCSIReq *req;
bool progress = false;

while ((req = virtio_scsi_pop_req(s, vq))) {
progress = true;
virtio_scsi_handle_ctrl_req(s, req);
}
return progress;
}

static void virtio_scsi_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
Expand Down Expand Up @@ -591,17 +594,19 @@ static void virtio_scsi_handle_cmd_req_submit(VirtIOSCSI *s, VirtIOSCSIReq *req)
scsi_req_unref(sreq);
}

void virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq)
bool virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq)
{
VirtIOSCSIReq *req, *next;
int ret = 0;
bool progress = false;

QTAILQ_HEAD(, VirtIOSCSIReq) reqs = QTAILQ_HEAD_INITIALIZER(reqs);

do {
virtio_queue_set_notification(vq, 0);

while ((req = virtio_scsi_pop_req(s, vq))) {
progress = true;
ret = virtio_scsi_handle_cmd_req_prepare(s, req);
if (!ret) {
QTAILQ_INSERT_TAIL(&reqs, req, next);
Expand All @@ -624,6 +629,7 @@ void virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq)
QTAILQ_FOREACH_SAFE(req, &reqs, next, next) {
virtio_scsi_handle_cmd_req_submit(s, req);
}
return progress;
}

static void virtio_scsi_handle_cmd(VirtIODevice *vdev, VirtQueue *vq)
Expand Down Expand Up @@ -752,11 +758,13 @@ void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
virtio_scsi_release(s);
}

void virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq)
bool virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq)
{
if (s->events_dropped) {
virtio_scsi_push_event(s, NULL, VIRTIO_SCSI_T_NO_EVENT, 0);
return true;
}
return false;
}

static void virtio_scsi_handle_event(VirtIODevice *vdev, VirtQueue *vq)
Expand Down
15 changes: 9 additions & 6 deletions hw/virtio/virtio.c
View file
Expand Up @@ -97,7 +97,7 @@ struct VirtQueue

uint16_t vector;
VirtIOHandleOutput handle_output;
VirtIOHandleOutput handle_aio_output;
VirtIOHandleAIOOutput handle_aio_output;
VirtIODevice *vdev;
EventNotifier guest_notifier;
EventNotifier host_notifier;
Expand Down Expand Up @@ -1287,14 +1287,16 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
virtio_queue_update_rings(vdev, n);
}

static void virtio_queue_notify_aio_vq(VirtQueue *vq)
static bool virtio_queue_notify_aio_vq(VirtQueue *vq)
{
if (vq->vring.desc && vq->handle_aio_output) {
VirtIODevice *vdev = vq->vdev;

trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
vq->handle_aio_output(vdev, vq);
return vq->handle_aio_output(vdev, vq);
}

return false;
}

static void virtio_queue_notify_vq(VirtQueue *vq)
Expand Down Expand Up @@ -2125,16 +2127,17 @@ static bool virtio_queue_host_notifier_aio_poll(void *opaque)
{
EventNotifier *n = opaque;
VirtQueue *vq = container_of(n, VirtQueue, host_notifier);
bool progress;

if (virtio_queue_empty(vq)) {
return false;
}

virtio_queue_notify_aio_vq(vq);
progress = virtio_queue_notify_aio_vq(vq);

/* In case the handler function re-enabled notifications */
virtio_queue_set_notification(vq, 0);
return true;
return progress;
}

static void virtio_queue_host_notifier_aio_poll_end(EventNotifier *n)
Expand All @@ -2146,7 +2149,7 @@ static void virtio_queue_host_notifier_aio_poll_end(EventNotifier *n)
}

void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
VirtIOHandleOutput handle_output)
VirtIOHandleAIOOutput handle_output)
{
if (handle_output) {
vq->handle_aio_output = handle_output;
Expand Down
2 changes: 1 addition & 1 deletion include/hw/virtio/virtio-blk.h
View file
Expand Up @@ -80,6 +80,6 @@ typedef struct MultiReqBuffer {
bool is_write;
} MultiReqBuffer;

void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq);
bool virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq);

#endif
6 changes: 3 additions & 3 deletions include/hw/virtio/virtio-scsi.h
View file
Expand Up @@ -126,9 +126,9 @@ void virtio_scsi_common_realize(DeviceState *dev, Error **errp,
VirtIOHandleOutput cmd);

void virtio_scsi_common_unrealize(DeviceState *dev, Error **errp);
void virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq);
void virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq);
void virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq);
bool virtio_scsi_handle_event_vq(VirtIOSCSI *s, VirtQueue *vq);
bool virtio_scsi_handle_cmd_vq(VirtIOSCSI *s, VirtQueue *vq);
bool virtio_scsi_handle_ctrl_vq(VirtIOSCSI *s, VirtQueue *vq);
void virtio_scsi_init_req(VirtIOSCSI *s, VirtQueue *vq, VirtIOSCSIReq *req);
void virtio_scsi_free_req(VirtIOSCSIReq *req);
void virtio_scsi_push_event(VirtIOSCSI *s, SCSIDevice *dev,
Expand Down
4 changes: 2 additions & 2 deletions include/hw/virtio/virtio.h
View file
Expand Up @@ -154,6 +154,7 @@ void virtio_error(VirtIODevice *vdev, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);

typedef void (*VirtIOHandleOutput)(VirtIODevice *, VirtQueue *);
typedef bool (*VirtIOHandleAIOOutput)(VirtIODevice *, VirtQueue *);

VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
VirtIOHandleOutput handle_output);
Expand Down Expand Up @@ -284,8 +285,7 @@ bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev);
EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq);
void virtio_queue_host_notifier_read(EventNotifier *n);
void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
void (*fn)(VirtIODevice *,
VirtQueue *));
VirtIOHandleAIOOutput handle_output);
VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t vector);
VirtQueue *virtio_vector_next_queue(VirtQueue *vq);

Expand Down

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