svn commit: r265295 - stable/9/sys/dev/virtio

[Bryan Venteicher]

Author: bryanv
Date: Sun May  4 00:10:25 2014
New Revision: 265295
URL: http://svnweb.freebsd.org/changeset/base/265295

Log:
  MFC r255166, r255109:
  
   - Fix unintended compiler constant folding
   - Add support for postponing VirtIO virtqueue interrupts

Modified:
  stable/9/sys/dev/virtio/virtqueue.c
  stable/9/sys/dev/virtio/virtqueue.h
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/dev/   (props changed)

Modified: stable/9/sys/dev/virtio/virtqueue.c
==============================================================================
--- stable/9/sys/dev/virtio/virtqueue.c	Sun May  4 00:09:17 2014	(r265294)
+++ stable/9/sys/dev/virtio/virtqueue.c	Sun May  4 00:10:25 2014	(r265295)
@@ -127,7 +127,7 @@ static uint16_t	vq_ring_enqueue_segments
 static int	vq_ring_use_indirect(struct virtqueue *, int);
 static void	vq_ring_enqueue_indirect(struct virtqueue *, void *,
 		    struct sglist *, int, int);
-static int 	vq_ring_enable_interrupt(struct virtqueue *, uint16_t);
+static int	vq_ring_enable_interrupt(struct virtqueue *, uint16_t);
 static int	vq_ring_must_notify_host(struct virtqueue *);
 static void	vq_ring_notify_host(struct virtqueue *);
 static void	vq_ring_free_chain(struct virtqueue *, uint16_t);
@@ -440,28 +440,38 @@ virtqueue_enable_intr(struct virtqueue *
 }
 
 int
-virtqueue_postpone_intr(struct virtqueue *vq)
+virtqueue_postpone_intr(struct virtqueue *vq, vq_postpone_t hint)
 {
 	uint16_t ndesc, avail_idx;
 
-	/*
-	 * Request the next interrupt be postponed until at least half
-	 * of the available descriptors have been consumed.
-	 */
 	avail_idx = vq->vq_ring.avail->idx;
-	ndesc = (uint16_t)(avail_idx - vq->vq_used_cons_idx) / 2;
+	ndesc = (uint16_t)(avail_idx - vq->vq_used_cons_idx);
+
+	switch (hint) {
+	case VQ_POSTPONE_SHORT:
+		ndesc = ndesc / 4;
+		break;
+	case VQ_POSTPONE_LONG:
+		ndesc = (ndesc * 3) / 4;
+		break;
+	case VQ_POSTPONE_EMPTIED:
+		break;
+	}
 
 	return (vq_ring_enable_interrupt(vq, ndesc));
 }
 
+/*
+ * Note this is only considered a hint to the host.
+ */
 void
 virtqueue_disable_intr(struct virtqueue *vq)
 {
 
-	/*
-	 * Note this is only considered a hint to the host.
-	 */
-	if ((vq->vq_flags & VIRTQUEUE_FLAG_EVENT_IDX) == 0)
+	if (vq->vq_flags & VIRTQUEUE_FLAG_EVENT_IDX) {
+		vring_used_event(&vq->vq_ring) = vq->vq_used_cons_idx -
+		    vq->vq_nentries - 1;
+	} else
 		vq->vq_ring.avail->flags |= VRING_AVAIL_F_NO_INTERRUPT;
 }
 

Modified: stable/9/sys/dev/virtio/virtqueue.h
==============================================================================
--- stable/9/sys/dev/virtio/virtqueue.h	Sun May  4 00:09:17 2014	(r265294)
+++ stable/9/sys/dev/virtio/virtqueue.h	Sun May  4 00:10:25 2014	(r265295)
@@ -41,6 +41,16 @@ struct sglist;
 /* Device callback for a virtqueue interrupt. */
 typedef void virtqueue_intr_t(void *);
 
+/*
+ * Hint on how long the next interrupt should be postponed. This is
+ * only used when the EVENT_IDX feature is negotiated.
+ */
+typedef enum {
+	VQ_POSTPONE_SHORT,
+	VQ_POSTPONE_LONG,
+	VQ_POSTPONE_EMPTIED	/* Until all available desc are used. */
+} vq_postpone_t;
+
 #define VIRTQUEUE_MAX_NAME_SZ	32
 
 /* One for each virtqueue the device wishes to allocate. */
@@ -73,7 +83,7 @@ int	 virtqueue_reinit(struct virtqueue *
 int	 virtqueue_intr_filter(struct virtqueue *vq);
 void	 virtqueue_intr(struct virtqueue *vq);
 int	 virtqueue_enable_intr(struct virtqueue *vq);
-int	 virtqueue_postpone_intr(struct virtqueue *vq);
+int	 virtqueue_postpone_intr(struct virtqueue *vq, vq_postpone_t hint);
 void	 virtqueue_disable_intr(struct virtqueue *vq);
 
 /* Get physical address of the virtqueue ring. */