summaryrefslogtreecommitdiff
path: root/drivers/hv/ring_buffer.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/hv/ring_buffer.c')
-rw-r--r--drivers/hv/ring_buffer.c169
1 files changed, 60 insertions, 109 deletions
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 1f450c39a9b0..12eb8caa4263 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -29,6 +29,7 @@
#include <linux/uio.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
+#include <linux/prefetch.h>
#include "hyperv_vmbus.h"
@@ -94,30 +95,6 @@ hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
ring_info->ring_buffer->write_index = next_write_location;
}
-/* Get the next read location for the specified ring buffer. */
-static inline u32
-hv_get_next_read_location(const struct hv_ring_buffer_info *ring_info)
-{
- return ring_info->ring_buffer->read_index;
-}
-
-/*
- * Get the next read location + offset for the specified ring buffer.
- * This allows the caller to skip.
- */
-static inline u32
-hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info *ring_info,
- u32 offset)
-{
- u32 next = ring_info->ring_buffer->read_index;
-
- next += offset;
- if (next >= ring_info->ring_datasize)
- next -= ring_info->ring_datasize;
-
- return next;
-}
-
/* Set the next read location for the specified ring buffer. */
static inline void
hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
@@ -142,29 +119,6 @@ hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
}
/*
- * Helper routine to copy to source from ring buffer.
- * Assume there is enough room. Handles wrap-around in src case only!!
- */
-static u32 hv_copyfrom_ringbuffer(
- const struct hv_ring_buffer_info *ring_info,
- void *dest,
- u32 destlen,
- u32 start_read_offset)
-{
- void *ring_buffer = hv_get_ring_buffer(ring_info);
- u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
-
- memcpy(dest, ring_buffer + start_read_offset, destlen);
-
- start_read_offset += destlen;
- if (start_read_offset >= ring_buffer_size)
- start_read_offset -= ring_buffer_size;
-
- return start_read_offset;
-}
-
-
-/*
* Helper routine to copy from source to ring buffer.
* Assume there is enough room. Handles wrap-around in dest case only!!
*/
@@ -334,33 +288,22 @@ 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)
{
- u32 bytes_avail_toread;
- u32 next_read_location;
- u64 prev_indices = 0;
- struct vmpacket_descriptor desc;
- u32 offset;
- u32 packetlen;
- struct hv_ring_buffer_info *inring_info = &channel->inbound;
-
- if (buflen <= 0)
+ struct vmpacket_descriptor *desc;
+ u32 packetlen, offset;
+
+ if (unlikely(buflen == 0))
return -EINVAL;
*buffer_actual_len = 0;
*requestid = 0;
- bytes_avail_toread = hv_get_bytes_to_read(inring_info);
/* Make sure there is something to read */
- if (bytes_avail_toread < sizeof(desc)) {
+ desc = hv_pkt_iter_first(channel);
+ if (desc == NULL) {
/*
* No error is set when there is even no header, drivers are
* supposed to analyze buffer_actual_len.
@@ -368,48 +311,22 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
return 0;
}
- 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),
- next_read_location);
-
- offset = raw ? 0 : (desc.offset8 << 3);
- packetlen = (desc.len8 << 3) - offset;
+ offset = raw ? 0 : (desc->offset8 << 3);
+ packetlen = (desc->len8 << 3) - offset;
*buffer_actual_len = packetlen;
- *requestid = desc.trans_id;
-
- if (bytes_avail_toread < packetlen + offset)
- return -EAGAIN;
+ *requestid = desc->trans_id;
- if (packetlen > buflen)
+ if (unlikely(packetlen > buflen))
return -ENOBUFS;
- next_read_location =
- hv_get_next_readlocation_withoffset(inring_info, offset);
+ /* since ring is double mapped, only one copy is necessary */
+ memcpy(buffer, (const char *)desc + offset, packetlen);
- next_read_location = hv_copyfrom_ringbuffer(inring_info,
- buffer,
- packetlen,
- next_read_location);
+ /* Advance ring index to next packet descriptor */
+ __hv_pkt_iter_next(channel, desc);
- next_read_location = hv_copyfrom_ringbuffer(inring_info,
- &prev_indices,
- sizeof(u64),
- next_read_location);
-
- /*
- * 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_mb();
-
- /* Update the read index */
- hv_set_next_read_location(inring_info, next_read_location);
-
- hv_signal_on_read(channel);
+ /* Notify host of update */
+ hv_pkt_iter_close(channel);
return 0;
}
@@ -440,14 +357,16 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info *rbi)
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);
+ struct vmpacket_descriptor *desc;
if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
return NULL;
- return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+ desc = hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+ if (desc)
+ prefetch((char *)desc + (desc->len8 << 3));
+
+ return desc;
}
EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
@@ -471,10 +390,7 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
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;
+ return hv_pkt_iter_first(channel);
}
EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
@@ -484,6 +400,7 @@ EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
void hv_pkt_iter_close(struct vmbus_channel *channel)
{
struct hv_ring_buffer_info *rbi = &channel->inbound;
+ u32 orig_write_sz = hv_get_bytes_to_write(rbi);
/*
* Make sure all reads are done before we update the read index since
@@ -493,6 +410,40 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
virt_rmb();
rbi->ring_buffer->read_index = rbi->priv_read_index;
- hv_signal_on_read(channel);
+ /*
+ * Issue a full memory barrier before making the signaling decision.
+ * Here is the reason for having this barrier:
+ * If the reading of the pend_sz (in this function)
+ * were to be reordered and read before we commit the new read
+ * index (in the calling function) we could
+ * have a problem. If the host were to set the pending_sz after we
+ * have sampled pending_sz and go to sleep before we commit the
+ * read index, we could miss sending the interrupt. Issue a full
+ * memory barrier to address this.
+ */
+ virt_mb();
+
+ /* If host has disabled notifications then skip */
+ if (rbi->ring_buffer->interrupt_mask)
+ return;
+
+ if (rbi->ring_buffer->feature_bits.feat_pending_send_sz) {
+ u32 pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
+
+ /*
+ * If there was space before we began iteration,
+ * then host was not blocked. Also handles case where
+ * pending_sz is zero then host has nothing pending
+ * and does not need to be signaled.
+ */
+ if (orig_write_sz > pending_sz)
+ return;
+
+ /* If pending write will not fit, don't give false hope. */
+ if (hv_get_bytes_to_write(rbi) < pending_sz)
+ return;
+ }
+
+ vmbus_setevent(channel);
}
EXPORT_SYMBOL_GPL(hv_pkt_iter_close);