From 3f44d13dda83d390cc9563e56e7d337e4f6223f4 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= Date: Wed, 20 Jul 2022 08:59:38 +0200 Subject: vhost: add vhost_svq_poll MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit It allows the Shadow Control VirtQueue to wait for the device to use the available buffers. Signed-off-by: Eugenio Pérez Reviewed-by: Michael S. Tsirkin Signed-off-by: Jason Wang --- hw/virtio/vhost-shadow-virtqueue.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 'hw/virtio/vhost-shadow-virtqueue.c') diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c index c3a75ca..cc2ee47 100644 --- a/hw/virtio/vhost-shadow-virtqueue.c +++ b/hw/virtio/vhost-shadow-virtqueue.c @@ -486,6 +486,33 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq, } /** + * Poll the SVQ for one device used buffer. + * + * This function race with main event loop SVQ polling, so extra + * synchronization is needed. + * + * Return the length written by the device. + */ +size_t vhost_svq_poll(VhostShadowVirtqueue *svq) +{ + int64_t start_us = g_get_monotonic_time(); + do { + uint32_t len; + VirtQueueElement *elem = vhost_svq_get_buf(svq, &len); + if (elem) { + return len; + } + + if (unlikely(g_get_monotonic_time() - start_us > 10e6)) { + return 0; + } + + /* Make sure we read new used_idx */ + smp_rmb(); + } while (true); +} + +/** * Forward used buffers. * * @n: hdev call event notifier, the one that device set to notify svq. -- cgit v1.1