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virtio-blk: remove batch notification BH

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There is a batching mechanism for virtio-blk Used Buffer Notifications
that is no longer needed because the previous commit added batching to
virtio_notify_irqfd().

Note that this mechanism was rarely used in practice because it is only
enabled when EVENT_IDX is not negotiated by the driver. Modern drivers
enable EVENT_IDX.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-ID: <20230913200045.1024233-5-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2023-09-13 16:00:45 -04:00 committed by Kevin Wolf
parent 84d61e5f36
commit 073458da56
1 changed files with 1 additions and 47 deletions
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48
hw/block/dataplane/virtio-blk.c
View file

@ -31,9 +31,6 @@ struct VirtIOBlockDataPlane {
VirtIOBlkConf *conf;
VirtIODevice *vdev;
QEMUBH *bh; /* bh for guest notification */
unsigned long *batch_notify_vqs;
bool batch_notifications;
/* Note that these EventNotifiers are assigned by value. This is
* fine as long as you do not call event_notifier_cleanup on them
@ -47,36 +44,7 @@ struct VirtIOBlockDataPlane {
/* Raise an interrupt to signal guest, if necessary */
void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq)
{
if (s->batch_notifications) {
set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs);
qemu_bh_schedule(s->bh);
} else {
virtio_notify_irqfd(s->vdev, vq);
}
}
static void notify_guest_bh(void *opaque)
{
VirtIOBlockDataPlane *s = opaque;
unsigned nvqs = s->conf->num_queues;
unsigned long bitmap[BITS_TO_LONGS(nvqs)];
unsigned j;
memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
memset(s->batch_notify_vqs, 0, sizeof(bitmap));
for (j = 0; j < nvqs; j += BITS_PER_LONG) {
unsigned long bits = bitmap[j / BITS_PER_LONG];
while (bits != 0) {
unsigned i = j + ctzl(bits);
VirtQueue *vq = virtio_get_queue(s->vdev, i);
virtio_notify_irqfd(s->vdev, vq);
bits &= bits - 1; /* clear right-most bit */
}
}
virtio_notify_irqfd(s->vdev, vq);
}
/* Context: QEMU global mutex held */
@ -126,9 +94,6 @@ bool virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
} else {
s->ctx = qemu_get_aio_context();
}
s->bh = aio_bh_new_guarded(s->ctx, notify_guest_bh, s,
&DEVICE(vdev)->mem_reentrancy_guard);
s->batch_notify_vqs = bitmap_new(conf->num_queues);
*dataplane = s;
@ -146,8 +111,6 @@ void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
vblk = VIRTIO_BLK(s->vdev);
assert(!vblk->dataplane_started);
g_free(s->batch_notify_vqs);
qemu_bh_delete(s->bh);
if (s->iothread) {
object_unref(OBJECT(s->iothread));
}
@ -173,12 +136,6 @@ int virtio_blk_data_plane_start(VirtIODevice *vdev)
s->starting = true;
if (!virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) {
s->batch_notifications = true;
} else {
s->batch_notifications = false;
}
/* Set up guest notifier (irq) */
r = k->set_guest_notifiers(qbus->parent, nvqs, true);
if (r != 0) {
@ -370,9 +327,6 @@ void virtio_blk_data_plane_stop(VirtIODevice *vdev)
aio_context_release(s->ctx);
qemu_bh_cancel(s->bh);
notify_guest_bh(s); /* final chance to notify guest */
/* Clean up guest notifier (irq) */
k->set_guest_notifiers(qbus->parent, nvqs, false);