在 2022/7/7 02:39, Eugenio Pérez 写道:
It allows the Shadow Control VirtQueue to wait the device to use the commands
that restore the net device state after a live migration.
Signed-off-by: Eugenio Pérez <epere...@redhat.com>
---
hw/virtio/vhost-shadow-virtqueue.h | 1 +
hw/virtio/vhost-shadow-virtqueue.c | 54 ++++++++++++++++++++++++++++--
2 files changed, 52 insertions(+), 3 deletions(-)
diff --git a/hw/virtio/vhost-shadow-virtqueue.h
b/hw/virtio/vhost-shadow-virtqueue.h
index d01d2370db..c8668fbdd6 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -100,6 +100,7 @@ void vhost_svq_push_elem(VhostShadowVirtqueue *svq,
const VirtQueueElement *elem, uint32_t len);
int vhost_svq_inject(VhostShadowVirtqueue *svq, const struct iovec *iov,
size_t out_num, size_t in_num, void *opaque);
+ssize_t vhost_svq_poll(VhostShadowVirtqueue *svq);
void vhost_svq_set_svq_kick_fd(VhostShadowVirtqueue *svq, int svq_kick_fd);
void vhost_svq_set_svq_call_fd(VhostShadowVirtqueue *svq, int call_fd);
void vhost_svq_get_vring_addr(const VhostShadowVirtqueue *svq,
diff --git a/hw/virtio/vhost-shadow-virtqueue.c
b/hw/virtio/vhost-shadow-virtqueue.c
index bd9e34b413..ed7f1d0bc9 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -10,6 +10,8 @@
#include "qemu/osdep.h"
#include "hw/virtio/vhost-shadow-virtqueue.h"
+#include <glib/gpoll.h>
+
#include "qemu/error-report.h"
#include "qapi/error.h"
#include "qemu/main-loop.h"
@@ -490,10 +492,11 @@ void vhost_svq_push_elem(VhostShadowVirtqueue *svq,
}
}
-static void vhost_svq_flush(VhostShadowVirtqueue *svq,
- bool check_for_avail_queue)
+static size_t vhost_svq_flush(VhostShadowVirtqueue *svq,
+ bool check_for_avail_queue)
{
VirtQueue *vq = svq->vq;
+ size_t ret = 0;
/* Forward as many used buffers as possible. */
do {
@@ -510,7 +513,7 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
"More than %u used buffers obtained in a %u size
SVQ",
i, svq->vring.num);
virtqueue_flush(vq, svq->vring.num);
- return;
+ return ret;
}
svq_elem = vhost_svq_get_buf(svq, &len);
@@ -520,6 +523,7 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
elem = g_steal_pointer(&svq_elem.opaque);
virtqueue_fill(vq, elem, len, i++);
+ ret++;
}
virtqueue_flush(vq, i);
@@ -533,6 +537,50 @@ static void vhost_svq_flush(VhostShadowVirtqueue *svq,
vhost_handle_guest_kick(svq);
}
} while (!vhost_svq_enable_notification(svq));
+
+ return ret;
+}
+
+/**
+ * Poll the SVQ for device used buffers.
+ *
+ * This function race with main event loop SVQ polling, so extra
+ * synchronization is needed.
+ *
+ * Return the number of descriptors read from the device.
+ */
+ssize_t vhost_svq_poll(VhostShadowVirtqueue *svq)
+{
+ int fd = event_notifier_get_fd(&svq->hdev_call);
+ GPollFD poll_fd = {
+ .fd = fd,
+ .events = G_IO_IN,
+ };
+ assert(fd >= 0);
+ int r = g_poll(&poll_fd, 1, -1);
Any reason we can't simply (busy) polling the used ring here? It might
help to reduce the latency (and it is what kernel driver uses).
Thanks
+
+ if (unlikely(r < 0)) {
+ error_report("Cannot poll device call fd "G_POLLFD_FORMAT": (%d) %s",
+ poll_fd.fd, errno, g_strerror(errno));
+ return -errno;
+ }
+
+ if (r == 0) {
+ return 0;
+ }
+
+ if (unlikely(poll_fd.revents & ~(G_IO_IN))) {
+ error_report(
+ "Error polling device call fd "G_POLLFD_FORMAT": revents=%d",
+ poll_fd.fd, poll_fd.revents);
+ return -1;
+ }
+
+ /*
+ * Max return value of vhost_svq_flush is (uint16_t)-1, so it's safe to
+ * convert to ssize_t.
+ */
+ return vhost_svq_flush(svq, false);
}
/**
