From: Jason Wang <jasowang@redhat.com>
To: kvm@vger.kernel.org, mst@redhat.com,
virtualization@lists.linux-foundation.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: RAPOPORT@il.ibm.com, yang.zhang.wz@gmail.com,
Jason Wang <jasowang@redhat.com>
Subject: [PATCH V3 2/3] vhost: introduce vhost_vq_avail_empty()
Date: Fri, 26 Feb 2016 16:42:43 +0800 [thread overview]
Message-ID: <1456476164-17242-3-git-send-email-jasowang@redhat.com> (raw)
In-Reply-To: <1456476164-17242-1-git-send-email-jasowang@redhat.com>
This patch introduces a helper which will return true if we're sure
that the available ring is empty for a specific vq. When we're not
sure, e.g vq access failure, return false instead. This could be used
for busy polling code to exit the busy loop.
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/vhost/vhost.c | 14 ++++++++++++++
drivers/vhost/vhost.h | 1 +
2 files changed, 15 insertions(+)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 90ac092..c4ff9f2 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1633,6 +1633,20 @@ void vhost_add_used_and_signal_n(struct vhost_dev *dev,
}
EXPORT_SYMBOL_GPL(vhost_add_used_and_signal_n);
+/* return true if we're sure that available ring is empty */
+bool vhost_vq_avail_empty(struct vhost_dev *dev, struct vhost_virtqueue *vq)
+{
+ __virtio16 avail_idx;
+ int r;
+
+ r = __get_user(avail_idx, &vq->avail->idx);
+ if (r)
+ return false;
+
+ return vhost16_to_cpu(vq, avail_idx) == vq->avail_idx;
+}
+EXPORT_SYMBOL_GPL(vhost_vq_avail_empty);
+
/* OK, now we need to know about added descriptors. */
bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
{
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 43284ad..a7a43f0 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -159,6 +159,7 @@ void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
struct vring_used_elem *heads, unsigned count);
void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
+bool vhost_vq_avail_empty(struct vhost_dev *, struct vhost_virtqueue *);
bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
--
2.5.0
next prev parent reply other threads:[~2016-02-26 8:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-26 8:42 [PATCH V3 0/3] basic busy polling support for vhost_net Jason Wang
2016-02-26 8:42 ` [PATCH V3 1/3] vhost: introduce vhost_has_work() Jason Wang
2016-02-26 8:42 ` Jason Wang [this message]
2016-02-26 8:42 ` [PATCH V3 3/3] vhost_net: basic polling support Jason Wang
2016-02-28 14:09 ` Michael S. Tsirkin
2016-02-29 5:15 ` Jason Wang
2016-02-29 9:03 ` Michael S. Tsirkin
2016-02-28 21:56 ` Christian Borntraeger
2016-02-29 5:17 ` Jason Wang
2016-02-26 16:45 ` [PATCH V3 0/3] basic busy polling support for vhost_net David Miller
2016-02-28 9:12 ` Michael S. Tsirkin
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