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virtio: improve virtio devices initialization time 

The loading time of a VM is quite significant when its virtio
devices use a large amount of virt-queues (e.g. a virtio-serial
device with max_ports=511). Most of the time is spend in the
creation of all the required event notifiers (ioeventfd and memory
regions).

This patch pack all the changes to the memory regions in a
single memory transaction.

Reported-by: Sitong Liu
Reported-by: Xiaoling Gao
Signed-off-by: Gal Hammer <ghammer@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Tested-by: Greg Kurz <groug@kaod.org>
This commit is contained in:
Gal Hammer 2018-01-29 16:20:57 +02:00 committed by Michael S. Tsirkin
parent 76143618a5
commit 710fccf80d
1 changed files with 20 additions and 2 deletions
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22
hw/virtio/virtio.c
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@ -2572,8 +2572,9 @@ static Property virtio_properties[] = {
static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
{
VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev)));
int n, r, err;
int i, n, r, err;
memory_region_transaction_begin();
for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
VirtQueue *vq = &vdev->vq[n];
if (!virtio_queue_get_num(vdev, n)) {
@ -2596,9 +2597,11 @@ static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev)
}
event_notifier_set(&vq->host_notifier);
}
memory_region_transaction_commit();
return 0;
assign_error:
i = n; /* save n for a second iteration after transaction is committed. */
while (--n >= 0) {
VirtQueue *vq = &vdev->vq[n];
if (!virtio_queue_get_num(vdev, n)) {
@ -2608,7 +2611,14 @@ assign_error:
event_notifier_set_handler(&vq->host_notifier, NULL);
r = virtio_bus_set_host_notifier(qbus, n, false);
assert(r >= 0);
virtio_bus_cleanup_host_notifier(qbus, n);
}
memory_region_transaction_commit();
while (--i >= 0) {
if (!virtio_queue_get_num(vdev, i)) {
continue;
}
virtio_bus_cleanup_host_notifier(qbus, i);
}
return err;
}
@ -2626,6 +2636,7 @@ static void virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev)
VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev)));
int n, r;
memory_region_transaction_begin();
for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
VirtQueue *vq = &vdev->vq[n];
@ -2635,6 +2646,13 @@ static void virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev)
event_notifier_set_handler(&vq->host_notifier, NULL);
r = virtio_bus_set_host_notifier(qbus, n, false);
assert(r >= 0);
}
memory_region_transaction_commit();
for (n = 0; n < VIRTIO_QUEUE_MAX; n++) {
if (!virtio_queue_get_num(vdev, n)) {
continue;
}
virtio_bus_cleanup_host_notifier(qbus, n);
}
}