* [PATCH 2/6] Drivers: hv: vmbus: Use READ_ONCE() to read variables that are volatile
2016-04-03 0:59 ` [PATCH 1/6] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer K. Y. Srinivasan
@ 2016-04-03 0:59 ` K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 3/6] Drivers: hv: vmbus: Use the new virt_xx barrier code K. Y. Srinivasan
` (3 subsequent siblings)
4 siblings, 0 replies; 7+ messages in thread
From: K. Y. Srinivasan @ 2016-04-03 0:59 UTC (permalink / raw)
To: gregkh, linux-kernel, devel, olaf, apw, vkuznets, jasowang
Cc: K. Y. Srinivasan
Use the READ_ONCE macro to access variabes that can change asynchronously.
This is the recommended mechanism for dealing with "unsafe" compiler
optimizations.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/ring_buffer.c | 6 +++---
1 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 544362c..6ea1b55 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -69,7 +69,7 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi)
static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
{
mb();
- if (rbi->ring_buffer->interrupt_mask)
+ if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
return false;
/* check interrupt_mask before read_index */
@@ -78,7 +78,7 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
* This is the only case we need to signal when the
* ring transitions from being empty to non-empty.
*/
- if (old_write == rbi->ring_buffer->read_index)
+ if (old_write == READ_ONCE(rbi->ring_buffer->read_index))
return true;
return false;
@@ -117,7 +117,7 @@ static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
*/
mb();
- pending_sz = rbi->ring_buffer->pending_send_sz;
+ pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
/* If the other end is not blocked on write don't bother. */
if (pending_sz == 0)
return false;
--
1.7.4.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 3/6] Drivers: hv: vmbus: Use the new virt_xx barrier code
2016-04-03 0:59 ` [PATCH 1/6] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 2/6] Drivers: hv: vmbus: Use READ_ONCE() to read variables that are volatile K. Y. Srinivasan
@ 2016-04-03 0:59 ` K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 4/6] Drivers: hv: vmbus: Export the vmbus_set_event() API K. Y. Srinivasan
` (2 subsequent siblings)
4 siblings, 0 replies; 7+ messages in thread
From: K. Y. Srinivasan @ 2016-04-03 0:59 UTC (permalink / raw)
To: gregkh, linux-kernel, devel, olaf, apw, vkuznets, jasowang
Cc: K. Y. Srinivasan
Use the virt_xx barriers that have been defined for use in virtual machines.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/ring_buffer.c | 14 +++++++-------
1 files changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 6ea1b55..8f518af 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -33,14 +33,14 @@
void hv_begin_read(struct hv_ring_buffer_info *rbi)
{
rbi->ring_buffer->interrupt_mask = 1;
- mb();
+ virt_mb();
}
u32 hv_end_read(struct hv_ring_buffer_info *rbi)
{
rbi->ring_buffer->interrupt_mask = 0;
- mb();
+ virt_mb();
/*
* Now check to see if the ring buffer is still empty.
@@ -68,12 +68,12 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi)
static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
{
- mb();
+ virt_mb();
if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
return false;
/* check interrupt_mask before read_index */
- rmb();
+ virt_rmb();
/*
* This is the only case we need to signal when the
* ring transitions from being empty to non-empty.
@@ -115,7 +115,7 @@ static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
* read index, we could miss sending the interrupt. Issue a full
* memory barrier to address this.
*/
- mb();
+ virt_mb();
pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
/* If the other end is not blocked on write don't bother. */
@@ -371,7 +371,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
sizeof(u64));
/* Issue a full memory barrier before updating the write index */
- mb();
+ virt_mb();
/* Now, update the write location */
hv_set_next_write_location(outring_info, next_write_location);
@@ -447,7 +447,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
* the writer may start writing to the read area once the read index
* is updated.
*/
- mb();
+ virt_mb();
/* Update the read index */
hv_set_next_read_location(inring_info, next_read_location);
--
1.7.4.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 4/6] Drivers: hv: vmbus: Export the vmbus_set_event() API
2016-04-03 0:59 ` [PATCH 1/6] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 2/6] Drivers: hv: vmbus: Use READ_ONCE() to read variables that are volatile K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 3/6] Drivers: hv: vmbus: Use the new virt_xx barrier code K. Y. Srinivasan
@ 2016-04-03 0:59 ` K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 5/6] Drivers: hv: vmbus: Move some ring buffer functions to hyperv.h K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 6/6] Drivers: hv: vmbus: Implement APIs to support "in place" consumption of vmbus packets K. Y. Srinivasan
4 siblings, 0 replies; 7+ messages in thread
From: K. Y. Srinivasan @ 2016-04-03 0:59 UTC (permalink / raw)
To: gregkh, linux-kernel, devel, olaf, apw, vkuznets, jasowang
Cc: K. Y. Srinivasan
In preparation for moving some ring buffer functionality out of the
vmbus driver, export the API for signaling the host.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/connection.c | 1 +
drivers/hv/hyperv_vmbus.h | 2 --
include/linux/hyperv.h | 1 +
3 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index d02f137..fcf8a02 100644
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -495,3 +495,4 @@ void vmbus_set_event(struct vmbus_channel *channel)
hv_do_hypercall(HVCALL_SIGNAL_EVENT, channel->sig_event, NULL);
}
+EXPORT_SYMBOL_GPL(vmbus_set_event);
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 8b07f9c..e5203e4 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -672,8 +672,6 @@ void vmbus_disconnect(void);
int vmbus_post_msg(void *buffer, size_t buflen);
-void vmbus_set_event(struct vmbus_channel *channel);
-
void vmbus_on_event(unsigned long data);
void vmbus_on_msg_dpc(unsigned long data);
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index a6b053c..4adeb6e 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1365,4 +1365,5 @@ extern __u32 vmbus_proto_version;
int vmbus_send_tl_connect_request(const uuid_le *shv_guest_servie_id,
const uuid_le *shv_host_servie_id);
+void vmbus_set_event(struct vmbus_channel *channel);
#endif /* _HYPERV_H */
--
1.7.4.1
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 5/6] Drivers: hv: vmbus: Move some ring buffer functions to hyperv.h
2016-04-03 0:59 ` [PATCH 1/6] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer K. Y. Srinivasan
` (2 preceding siblings ...)
2016-04-03 0:59 ` [PATCH 4/6] Drivers: hv: vmbus: Export the vmbus_set_event() API K. Y. Srinivasan
@ 2016-04-03 0:59 ` K. Y. Srinivasan
2016-04-03 0:59 ` [PATCH 6/6] Drivers: hv: vmbus: Implement APIs to support "in place" consumption of vmbus packets K. Y. Srinivasan
4 siblings, 0 replies; 7+ messages in thread
From: K. Y. Srinivasan @ 2016-04-03 0:59 UTC (permalink / raw)
To: gregkh, linux-kernel, devel, olaf, apw, vkuznets, jasowang
Cc: K. Y. Srinivasan
In preparation for implementing APIs for in-place consumption of VMBUS
packets, movve some ring buffer functionality into hyperv.h
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/ring_buffer.c | 55 ----------------------------------------------
include/linux/hyperv.h | 54 +++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+), 55 deletions(-)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 8f518af..dd255c9 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -84,52 +84,6 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
return false;
}
-/*
- * To optimize the flow management on the send-side,
- * when the sender is blocked because of lack of
- * sufficient space in the ring buffer, potential the
- * consumer of the ring buffer can signal the producer.
- * This is controlled by the following parameters:
- *
- * 1. pending_send_sz: This is the size in bytes that the
- * producer is trying to send.
- * 2. The feature bit feat_pending_send_sz set to indicate if
- * the consumer of the ring will signal when the ring
- * state transitions from being full to a state where
- * there is room for the producer to send the pending packet.
- */
-
-static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
-{
- u32 cur_write_sz;
- u32 pending_sz;
-
- /*
- * 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();
-
- pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
- /* If the other end is not blocked on write don't bother. */
- if (pending_sz == 0)
- return false;
-
- cur_write_sz = hv_get_bytes_to_write(rbi);
-
- if (cur_write_sz >= pending_sz)
- return true;
-
- return false;
-}
-
/* Get the next write location for the specified ring buffer. */
static inline u32
hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
@@ -180,15 +134,6 @@ hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
ring_info->ring_buffer->read_index = next_read_location;
}
-
-/* Get the start of the ring buffer. */
-static inline void *
-hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
-{
- return (void *)ring_info->ring_buffer->buffer;
-}
-
-
/* Get the size of the ring buffer. */
static inline u32
hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 4adeb6e..6797a30 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -1366,4 +1366,58 @@ extern __u32 vmbus_proto_version;
int vmbus_send_tl_connect_request(const uuid_le *shv_guest_servie_id,
const uuid_le *shv_host_servie_id);
void vmbus_set_event(struct vmbus_channel *channel);
+
+/* Get the start of the ring buffer. */
+static inline void *
+hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
+{
+ return (void *)ring_info->ring_buffer->buffer;
+}
+
+/*
+ * To optimize the flow management on the send-side,
+ * when the sender is blocked because of lack of
+ * sufficient space in the ring buffer, potential the
+ * consumer of the ring buffer can signal the producer.
+ * This is controlled by the following parameters:
+ *
+ * 1. pending_send_sz: This is the size in bytes that the
+ * producer is trying to send.
+ * 2. The feature bit feat_pending_send_sz set to indicate if
+ * the consumer of the ring will signal when the ring
+ * state transitions from being full to a state where
+ * there is room for the producer to send the pending packet.
+ */
+
+static inline bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
+{
+ u32 cur_write_sz;
+ u32 pending_sz;
+
+ /*
+ * 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();
+
+ pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
+ /* If the other end is not blocked on write don't bother. */
+ if (pending_sz == 0)
+ return false;
+
+ cur_write_sz = hv_get_bytes_to_write(rbi);
+
+ if (cur_write_sz >= pending_sz)
+ return true;
+
+ return false;
+}
+
#endif /* _HYPERV_H */
--
1.7.4.1
^ permalink raw reply related [flat|nested] 7+ messages in thread* [PATCH 6/6] Drivers: hv: vmbus: Implement APIs to support "in place" consumption of vmbus packets
2016-04-03 0:59 ` [PATCH 1/6] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer K. Y. Srinivasan
` (3 preceding siblings ...)
2016-04-03 0:59 ` [PATCH 5/6] Drivers: hv: vmbus: Move some ring buffer functions to hyperv.h K. Y. Srinivasan
@ 2016-04-03 0:59 ` K. Y. Srinivasan
4 siblings, 0 replies; 7+ messages in thread
From: K. Y. Srinivasan @ 2016-04-03 0:59 UTC (permalink / raw)
To: gregkh, linux-kernel, devel, olaf, apw, vkuznets, jasowang
Cc: K. Y. Srinivasan
Implement APIs for in-place consumption of vmbus packets. Currently, each
packet is copied and processed one at a time and as part of processing
each packet we potentially may signal the host (if it is waiting for
room to produce a packet).
These APIs help batched in-place processing of vmbus packets.
We also optimize host signaling by having a separate API to signal
the end of in-place consumption. With netvsc using these APIs,
on an iperf run on average I see about 20X reduction in checks to
signal the host.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
drivers/hv/ring_buffer.c | 1 +
include/linux/hyperv.h | 86 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 87 insertions(+), 0 deletions(-)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index dd255c9..fe586bf 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -132,6 +132,7 @@ hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
u32 next_read_location)
{
ring_info->ring_buffer->read_index = next_read_location;
+ ring_info->priv_read_index = next_read_location;
}
/* Get the size of the ring buffer. */
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 6797a30..b10954a 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -126,6 +126,8 @@ struct hv_ring_buffer_info {
u32 ring_datasize; /* < ring_size */
u32 ring_data_startoffset;
+ u32 priv_write_index;
+ u32 priv_read_index;
};
/*
@@ -1420,4 +1422,88 @@ static inline bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
return false;
}
+/*
+ * An API to support in-place processing of incoming VMBUS packets.
+ */
+#define VMBUS_PKT_TRAILER 8
+
+static inline struct vmpacket_descriptor *
+get_next_pkt_raw(struct vmbus_channel *channel)
+{
+ struct hv_ring_buffer_info *ring_info = &channel->inbound;
+ u32 read_loc = ring_info->priv_read_index;
+ void *ring_buffer = hv_get_ring_buffer(ring_info);
+ struct vmpacket_descriptor *cur_desc;
+ u32 packetlen;
+ u32 dsize = ring_info->ring_datasize;
+ u32 delta = read_loc - ring_info->ring_buffer->read_index;
+ u32 bytes_avail_toread = (hv_get_bytes_to_read(ring_info) - delta);
+
+ if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
+ return NULL;
+
+ if ((read_loc + sizeof(*cur_desc)) > dsize)
+ return NULL;
+
+ cur_desc = ring_buffer + read_loc;
+ packetlen = cur_desc->len8 << 3;
+
+ /*
+ * If the packet under consideration is wrapping around,
+ * return failure.
+ */
+ if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > (dsize - 1))
+ return NULL;
+
+ return cur_desc;
+}
+
+/*
+ * A helper function to step through packets "in-place"
+ * This API is to be called after each successful call
+ * get_next_pkt_raw().
+ */
+static inline void put_pkt_raw(struct vmbus_channel *channel,
+ struct vmpacket_descriptor *desc)
+{
+ struct hv_ring_buffer_info *ring_info = &channel->inbound;
+ u32 read_loc = ring_info->priv_read_index;
+ u32 packetlen = desc->len8 << 3;
+ u32 dsize = ring_info->ring_datasize;
+
+ if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > dsize)
+ BUG();
+ /*
+ * Include the packet trailer.
+ */
+ ring_info->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
+}
+
+/*
+ * This call commits the read index and potentially signals the host.
+ * Here is the pattern for using the "in-place" consumption APIs:
+ *
+ * while (get_next_pkt_raw() {
+ * process the packet "in-place";
+ * put_pkt_raw();
+ * }
+ * if (packets processed in place)
+ * commit_rd_index();
+ */
+static inline void commit_rd_index(struct vmbus_channel *channel)
+{
+ struct hv_ring_buffer_info *ring_info = &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();
+ ring_info->ring_buffer->read_index = ring_info->priv_read_index;
+
+ if (hv_need_to_signal_on_read(ring_info))
+ vmbus_set_event(channel);
+}
+
+
#endif /* _HYPERV_H */
--
1.7.4.1
^ permalink raw reply related [flat|nested] 7+ messages in thread