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Date: Fri, 22 Sep 2017 16:02:31 +0800
From: Jason Wang <jasowang@...hat.com>
To: mst@...hat.com, jasowang@...hat.com,
virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: kvm@...r.kernel.org
Subject: [PATCH net-next RFC 1/5] vhost: split out ring head fetching logic
This patch splits out ring head fetching logic and leave the
descriptor fetching and translation logic. This makes it is possible
to batch fetching the descriptor indices.
Signed-off-by: Jason Wang <jasowang@...hat.com>
---
drivers/vhost/vhost.c | 75 +++++++++++++++++++++++++++++++++------------------
drivers/vhost/vhost.h | 5 ++++
2 files changed, 54 insertions(+), 26 deletions(-)
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index d6dbb28..f87ec75 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1984,41 +1984,23 @@ static int get_indirect(struct vhost_virtqueue *vq,
return 0;
}
-/* This looks in the virtqueue and for the first available buffer, and converts
- * it to an iovec for convenient access. Since descriptors consist of some
- * number of output then some number of input descriptors, it's actually two
- * iovecs, but we pack them into one and note how many of each there were.
- *
- * This function returns the descriptor number found, or vq->num (which is
- * never a valid descriptor number) if none was found. A negative code is
- * returned on error. */
-int vhost_get_vq_desc(struct vhost_virtqueue *vq,
- struct iovec iov[], unsigned int iov_size,
- unsigned int *out_num, unsigned int *in_num,
- struct vhost_log *log, unsigned int *log_num)
+static unsigned int vhost_get_vq_head(struct vhost_virtqueue *vq, int *err)
{
- struct vring_desc desc;
- unsigned int i, head, found = 0;
- u16 last_avail_idx;
- __virtio16 avail_idx;
- __virtio16 ring_head;
- int ret, access;
-
- /* Check it isn't doing very strange things with descriptor numbers. */
- last_avail_idx = vq->last_avail_idx;
+ u16 last_avail_idx = vq->last_avail_idx;
+ __virtio16 avail_idx, ring_head;
if (vq->avail_idx == vq->last_avail_idx) {
if (unlikely(vhost_get_avail(vq, avail_idx, &vq->avail->idx))) {
vq_err(vq, "Failed to access avail idx at %p\n",
&vq->avail->idx);
- return -EFAULT;
+ goto err;
}
vq->avail_idx = vhost16_to_cpu(vq, avail_idx);
if (unlikely((u16)(vq->avail_idx - last_avail_idx) > vq->num)) {
vq_err(vq, "Guest moved used index from %u to %u",
last_avail_idx, vq->avail_idx);
- return -EFAULT;
+ goto err;
}
/* If there's nothing new since last we looked, return
@@ -2040,13 +2022,35 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
vq_err(vq, "Failed to read head: idx %d address %p\n",
last_avail_idx,
&vq->avail->ring[last_avail_idx % vq->num]);
- return -EFAULT;
+ goto err;
}
- head = vhost16_to_cpu(vq, ring_head);
+ return vhost16_to_cpu(vq, ring_head);
+err:
+ *err = -EFAULT;
+ return 0;
+}
+
+/* This looks in the virtqueue and for the first available buffer, and converts
+ * it to an iovec for convenient access. Since descriptors consist of some
+ * number of output then some number of input descriptors, it's actually two
+ * iovecs, but we pack them into one and note how many of each there were.
+ *
+ * This function returns the descriptor number found, or vq->num (which is
+ * never a valid descriptor number) if none was found. A negative code is
+ * returned on error. */
+int __vhost_get_vq_desc(struct vhost_virtqueue *vq,
+ struct iovec iov[], unsigned int iov_size,
+ unsigned int *out_num, unsigned int *in_num,
+ struct vhost_log *log, unsigned int *log_num,
+ __virtio16 head)
+{
+ struct vring_desc desc;
+ unsigned int i, found = 0;
+ int ret = 0, access;
/* If their number is silly, that's an error. */
- if (unlikely(head >= vq->num)) {
+ if (unlikely(head > vq->num)) {
vq_err(vq, "Guest says index %u > %u is available",
head, vq->num);
return -EINVAL;
@@ -2133,6 +2137,25 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
return head;
}
+EXPORT_SYMBOL_GPL(__vhost_get_vq_desc);
+
+int vhost_get_vq_desc(struct vhost_virtqueue *vq,
+ struct iovec iov[], unsigned int iov_size,
+ unsigned int *out_num, unsigned int *in_num,
+ struct vhost_log *log, unsigned int *log_num)
+{
+ int ret = 0;
+ unsigned int head = vhost_get_vq_head(vq, &ret);
+
+ if (ret)
+ return ret;
+
+ if (head == vq->num)
+ return head;
+
+ return __vhost_get_vq_desc(vq, iov, iov_size, out_num, in_num,
+ log, log_num, head);
+}
EXPORT_SYMBOL_GPL(vhost_get_vq_desc);
/* Reverse the effect of vhost_get_vq_desc. Useful for error handling. */
diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index d59a9cc..39ff897 100644
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -191,6 +191,11 @@ int vhost_get_vq_desc(struct vhost_virtqueue *,
struct iovec iov[], unsigned int iov_count,
unsigned int *out_num, unsigned int *in_num,
struct vhost_log *log, unsigned int *log_num);
+int __vhost_get_vq_desc(struct vhost_virtqueue *vq,
+ struct iovec iov[], unsigned int iov_count,
+ unsigned int *out_num, unsigned int *in_num,
+ struct vhost_log *log, unsigned int *log_num,
+ __virtio16 ring_head);
void vhost_discard_vq_desc(struct vhost_virtqueue *, int n);
int vhost_vq_init_access(struct vhost_virtqueue *);
--
2.7.4
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