[PATCH 1/3] Drivers: hv: vmbus: Enable explicit signaling policy for NIC channels

[kys@exchange.microsoft.com]

From: K. Y. Srinivasan <kys@microsoft.com>

For synthetic NIC channels, enable explicit signaling policy as netvsc wants to
explicitly control when the host is to be signaled.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/channel.c      |   18 ++++--------------
 drivers/hv/channel_mgmt.c |    2 ++
 drivers/hv/hyperv_vmbus.h |    3 ++-
 drivers/hv/ring_buffer.c  |   15 ++++++++++++---
 4 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index a68830c..da022d3 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -657,7 +657,7 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, num_vecs,
-				  &signal, lock);
+				  &signal, lock, channel->signal_policy);
 
 	/*
 	 * Signalling the host is conditional on many factors:
@@ -678,11 +678,6 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
 	 * mechanism which can hurt the performance otherwise.
 	 */
 
-	if (channel->signal_policy)
-		signal = true;
-	else
-		kick_q = true;
-
 	if (((ret == 0) && kick_q && signal) ||
 	    (ret && !is_hvsock_channel(channel)))
 		vmbus_setevent(channel);
@@ -775,7 +770,7 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3,
-				  &signal, lock);
+				  &signal, lock, channel->signal_policy);
 
 	/*
 	 * Signalling the host is conditional on many factors:
@@ -793,11 +788,6 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
 	 * enough condition that it should not matter.
 	 */
 
-	if (channel->signal_policy)
-		signal = true;
-	else
-		kick_q = true;
-
 	if (((ret == 0) && kick_q && signal) || (ret))
 		vmbus_setevent(channel);
 
@@ -859,7 +849,7 @@ int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3,
-				  &signal, lock);
+				  &signal, lock, channel->signal_policy);
 
 	if (ret == 0 && signal)
 		vmbus_setevent(channel);
@@ -924,7 +914,7 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel,
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3,
-				  &signal, lock);
+				  &signal, lock, channel->signal_policy);
 
 	if (ret == 0 && signal)
 		vmbus_setevent(channel);
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index b6c1211..8345869 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -406,6 +406,8 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel)
 	}
 
 	dev_type = hv_get_dev_type(&newchannel->offermsg.offer.if_type);
+	if (dev_type == HV_NIC)
+		set_channel_signal_state(newchannel, HV_SIGNAL_POLICY_EXPLICIT);
 
 	init_vp_index(newchannel, dev_type);
 
diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index dfa9fac..ddcc348 100644
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -529,7 +529,8 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info);
 
 int hv_ringbuffer_write(struct hv_ring_buffer_info *ring_info,
 		    struct kvec *kv_list,
-		    u32 kv_count, bool *signal, bool lock);
+		    u32 kv_count, bool *signal, bool lock,
+		    enum hv_signal_policy policy);
 
 int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 		       void *buffer, u32 buflen, u32 *buffer_actual_len,
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index fe586bf..e3edcae 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -66,12 +66,20 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi)
  *	   arrived.
  */
 
-static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
+static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi,
+			      enum hv_signal_policy policy)
 {
 	virt_mb();
 	if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
 		return false;
 
+	/*
+	 * When the client wants to control signaling,
+	 * we only honour the host interrupt mask.
+	 */
+	if (policy == HV_SIGNAL_POLICY_EXPLICIT)
+		return true;
+
 	/* check interrupt_mask before read_index */
 	virt_rmb();
 	/*
@@ -264,7 +272,8 @@ void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 
 /* Write to the ring buffer. */
 int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
-		    struct kvec *kv_list, u32 kv_count, bool *signal, bool lock)
+		    struct kvec *kv_list, u32 kv_count, bool *signal, bool lock,
+		    enum hv_signal_policy policy)
 {
 	int i = 0;
 	u32 bytes_avail_towrite;
@@ -326,7 +335,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 	if (lock)
 		spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 
-	*signal = hv_need_to_signal(old_write, outring_info);
+	*signal = hv_need_to_signal(old_write, outring_info, policy);
 	return 0;
 }
 
-- 
1.7.4.1