vmbus: introduce in-place packet iterator
This is mostly just a refactoring of previous functions
(get_pkt_next_raw, put_pkt_raw and commit_rd_index) to make it easier
to use for other drivers and NAPI.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 87799e8..c3f1a9e 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -32,6 +32,8 @@
#include "hyperv_vmbus.h"
+#define VMBUS_PKT_TRAILER 8
+
/*
* When we write to the ring buffer, check if the host needs to
* be signaled. Here is the details of this protocol:
@@ -336,6 +338,12 @@ int hv_ringbuffer_write(struct vmbus_channel *channel,
return 0;
}
+static inline void
+init_cached_read_index(struct hv_ring_buffer_info *rbi)
+{
+ rbi->cached_read_index = rbi->ring_buffer->read_index;
+}
+
int hv_ringbuffer_read(struct vmbus_channel *channel,
void *buffer, u32 buflen, u32 *buffer_actual_len,
u64 *requestid, bool raw)
@@ -366,7 +374,8 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
return ret;
}
- init_cached_read_index(channel);
+ init_cached_read_index(inring_info);
+
next_read_location = hv_get_next_read_location(inring_info);
next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
sizeof(desc),
@@ -410,3 +419,86 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
return ret;
}
+
+/*
+ * Determine number of bytes available in ring buffer after
+ * the current iterator (priv_read_index) location.
+ *
+ * This is similar to hv_get_bytes_to_read but with private
+ * read index instead.
+ */
+static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
+{
+ u32 priv_read_loc = rbi->priv_read_index;
+ u32 write_loc = READ_ONCE(rbi->ring_buffer->write_index);
+
+ if (write_loc >= priv_read_loc)
+ return write_loc - priv_read_loc;
+ else
+ return (rbi->ring_datasize - priv_read_loc) + write_loc;
+}
+
+/*
+ * Get first vmbus packet from ring buffer after read_index
+ *
+ * If ring buffer is empty, returns NULL and no other action needed.
+ */
+struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
+{
+ struct hv_ring_buffer_info *rbi = &channel->inbound;
+
+ /* set state for later hv_signal_on_read() */
+ init_cached_read_index(rbi);
+
+ if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
+ return NULL;
+
+ return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+}
+EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
+
+/*
+ * Get next vmbus packet from ring buffer.
+ *
+ * Advances the current location (priv_read_index) and checks for more
+ * data. If the end of the ring buffer is reached, then return NULL.
+ */
+struct vmpacket_descriptor *
+__hv_pkt_iter_next(struct vmbus_channel *channel,
+ const struct vmpacket_descriptor *desc)
+{
+ struct hv_ring_buffer_info *rbi = &channel->inbound;
+ u32 packetlen = desc->len8 << 3;
+ u32 dsize = rbi->ring_datasize;
+
+ /* bump offset to next potential packet */
+ rbi->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
+ if (rbi->priv_read_index >= dsize)
+ rbi->priv_read_index -= dsize;
+
+ /* more data? */
+ if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
+ return NULL;
+ else
+ return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+}
+EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
+
+/*
+ * Update host ring buffer after iterating over packets.
+ */
+void hv_pkt_iter_close(struct vmbus_channel *channel)
+{
+ struct hv_ring_buffer_info *rbi = &channel->inbound;
+
+ /*
+ * Make sure all reads are done before we update the read index since
+ * the writer may start writing to the read area once the read index
+ * is updated.
+ */
+ virt_rmb();
+ rbi->ring_buffer->read_index = rbi->priv_read_index;
+
+ hv_signal_on_read(channel);
+}
+EXPORT_SYMBOL_GPL(hv_pkt_iter_close);