virtio: disable virtqueue notifications during polling
This is a performance optimization to eliminate vmexits during polling. It also avoids spurious ioeventfd processing after polling ends. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 20161201192652.9509-12-stefanha@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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@ -2053,6 +2053,13 @@ static void virtio_queue_host_notifier_aio_read(EventNotifier *n)
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}
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}
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static void virtio_queue_host_notifier_aio_poll_begin(EventNotifier *n)
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{
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VirtQueue *vq = container_of(n, VirtQueue, host_notifier);
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virtio_queue_set_notification(vq, 0);
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}
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static bool virtio_queue_host_notifier_aio_poll(void *opaque)
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{
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EventNotifier *n = opaque;
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@ -2066,6 +2073,14 @@ static bool virtio_queue_host_notifier_aio_poll(void *opaque)
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return true;
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}
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static void virtio_queue_host_notifier_aio_poll_end(EventNotifier *n)
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{
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VirtQueue *vq = container_of(n, VirtQueue, host_notifier);
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/* Caller polls once more after this to catch requests that race with us */
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virtio_queue_set_notification(vq, 1);
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}
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void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
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VirtIOHandleOutput handle_output)
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{
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@ -2074,6 +2089,9 @@ void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext *ctx,
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aio_set_event_notifier(ctx, &vq->host_notifier, true,
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virtio_queue_host_notifier_aio_read,
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virtio_queue_host_notifier_aio_poll);
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aio_set_event_notifier_poll(ctx, &vq->host_notifier,
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virtio_queue_host_notifier_aio_poll_begin,
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virtio_queue_host_notifier_aio_poll_end);
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} else {
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aio_set_event_notifier(ctx, &vq->host_notifier, true, NULL, NULL);
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/* Test and clear notifier before after disabling event,
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