On Tue, 29 Nov 2011, Sasha Levin wrote:
+/*
+ * Each buffer in the virtqueues is actually a chain of descriptors. This
+ * function returns the next descriptor in the chain, or vq->vring.num if we're
+ * at the end.
+ */
+static unsigned next_desc(struct vring_desc *desc,
+ unsigned int i, unsigned int max)
+{
+ unsigned int next;
+
+ /* If this descriptor says it doesn't chain, we're done. */
+ if (!(desc[i].flags & VRING_DESC_F_NEXT))
+ return max;
+
+ /* Check they're not leading us off end of descriptors. */
+ next = desc[i].next;
+ /* Make sure compiler knows to grab that: we don't want it changing! */
+ wmb();
+
+ return next;
+}
+
Hi Sasha, where the rmb() then? Or maybe you wanted plain barrier() here?
On the kernel side.
Theres a mb there which happens there during the kick.
I guess we need to improve the comment in next_desc()?
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