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[Qemu-devel] virtio notiry question
From: |
jack.chen |
Subject: |
[Qemu-devel] virtio notiry question |
Date: |
Sun, 23 Sep 2018 19:48:29 +0800 |
hello ,when I read virtio source code ,I was confused about when back-end
notify front-end。
In function virtio_should_notify,if vq->signalled_used_valid == false
or vring_need_event(vring_get_used_event(vq), new, old) is true,notiry will
occur。but I can not understand when vq->signalled_used_valid will be false.
in virtqueue_flush,
if (unlikely((int16_t)(new - vq->signalled_used) < (uint16_t)(new - old)))
vq->signalled_used_valid = false;
but according code I think vq->signalled_used always equal
to vq->used_idx,that is vq->signalled_used_valid will always be true.
please help me understand it,thanks!
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