Drivers: hv: vmbus: On write cleanup the logic to interrupt the host

Signal the host when we determine the host is to be signaled.
The currrent code determines the need to signal in the ringbuffer
code and actually issues the signal elsewhere. This can result
in the host viewing this interrupt as spurious since the host may also
poll the channel. Make the necessary adjustments.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 89 deletions

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 5e482d7f60cb..8a8148f7b842 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -39,7 +39,7 @@
  * vmbus_setevent- Trigger an event notification on the specified
  * channel.
  */
-static void vmbus_setevent(struct vmbus_channel *channel)
+void vmbus_setevent(struct vmbus_channel *channel)
 {
 	struct hv_monitor_page *monitorpage;
 
@@ -65,6 +65,7 @@ static void vmbus_setevent(struct vmbus_channel *channel)
 		vmbus_set_event(channel);
 	}
 }
+EXPORT_SYMBOL_GPL(vmbus_setevent);
 
 /*
  * vmbus_open - Open the specified channel.
@@ -635,8 +636,6 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
 	u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));
 	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
-	int ret;
-	bool signal = false;
 	bool lock = channel->acquire_ring_lock;
 	int num_vecs = ((bufferlen != 0) ? 3 : 1);
 
@@ -656,41 +655,9 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
 	bufferlist[2].iov_base = &aligned_data;
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
-	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, num_vecs,
-				  &signal, lock, channel->signal_policy);
-
-	/*
-	 * Signalling the host is conditional on many factors:
-	 * 1. The ring state changed from being empty to non-empty.
-	 *    This is tracked by the variable "signal".
-	 * 2. The variable kick_q tracks if more data will be placed
-	 *    on the ring. We will not signal if more data is
-	 *    to be placed.
-	 *
-	 * Based on the channel signal state, we will decide
-	 * which signaling policy will be applied.
-	 *
-	 * If we cannot write to the ring-buffer; signal the host
-	 * even if we may not have written anything. This is a rare
-	 * enough condition that it should not matter.
-	 * NOTE: in this case, the hvsock channel is an exception, because
-	 * it looks the host side's hvsock implementation has a throttling
-	 * mechanism which can hurt the performance otherwise.
-	 *
-	 * KYS: Oct. 30, 2016:
-	 * It looks like Windows hosts have logic to deal with DOS attacks that
-	 * can be triggered if it receives interrupts when it is not expecting
-	 * the interrupt. The host expects interrupts only when the ring
-	 * transitions from empty to non-empty (or full to non full on the guest
-	 * to host ring).
-	 * So, base the signaling decision solely on the ring state until the
-	 * host logic is fixed.
-	 */
-
-	if (((ret == 0) && signal))
-		vmbus_setevent(channel);
+	return hv_ringbuffer_write(channel, bufferlist, num_vecs,
+				   lock, kick_q);
 
-	return ret;
 }
 EXPORT_SYMBOL(vmbus_sendpacket_ctl);
 
@@ -731,7 +698,6 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
 				     u32 flags,
 				     bool kick_q)
 {
-	int ret;
 	int i;
 	struct vmbus_channel_packet_page_buffer desc;
 	u32 descsize;
@@ -739,7 +705,6 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
 	u32 packetlen_aligned;
 	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
-	bool signal = false;
 	bool lock = channel->acquire_ring_lock;
 
 	if (pagecount > MAX_PAGE_BUFFER_COUNT)
@@ -777,38 +742,8 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
 	bufferlist[2].iov_base = &aligned_data;
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
-	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3,
-				  &signal, lock, channel->signal_policy);
-
-	/*
-	 * Signalling the host is conditional on many factors:
-	 * 1. The ring state changed from being empty to non-empty.
-	 *    This is tracked by the variable "signal".
-	 * 2. The variable kick_q tracks if more data will be placed
-	 *    on the ring. We will not signal if more data is
-	 *    to be placed.
-	 *
-	 * Based on the channel signal state, we will decide
-	 * which signaling policy will be applied.
-	 *
-	 * If we cannot write to the ring-buffer; signal the host
-	 * even if we may not have written anything. This is a rare
-	 * enough condition that it should not matter.
-	 *
-	 * KYS: Oct. 30, 2016:
-	 * It looks like Windows hosts have logic to deal with DOS attacks that
-	 * can be triggered if it receives interrupts when it is not expecting
-	 * the interrupt. The host expects interrupts only when the ring
-	 * transitions from empty to non-empty (or full to non full on the guest
-	 * to host ring).
-	 * So, base the signaling decision solely on the ring state until the
-	 * host logic is fixed.
-	 */
-
-	if (((ret == 0) && signal))
-		vmbus_setevent(channel);
-
-	return ret;
+	return hv_ringbuffer_write(channel, bufferlist, 3,
+				   lock, kick_q);
 }
 EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer_ctl);
 
@@ -839,12 +774,10 @@ int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
 			      u32 desc_size,
 			      void *buffer, u32 bufferlen, u64 requestid)
 {
-	int ret;
 	u32 packetlen;
 	u32 packetlen_aligned;
 	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
-	bool signal = false;
 	bool lock = channel->acquire_ring_lock;
 
 	packetlen = desc_size + bufferlen;
@@ -865,13 +798,8 @@ int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
 	bufferlist[2].iov_base = &aligned_data;
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
-	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3,
-				  &signal, lock, channel->signal_policy);
-
-	if (ret == 0 && signal)
-		vmbus_setevent(channel);
-
-	return ret;
+	return hv_ringbuffer_write(channel, bufferlist, 3,
+				   lock, true);
 }
 EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);
 
@@ -883,14 +811,12 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel,
 				struct hv_multipage_buffer *multi_pagebuffer,
 				void *buffer, u32 bufferlen, u64 requestid)
 {
-	int ret;
 	struct vmbus_channel_packet_multipage_buffer desc;
 	u32 descsize;
 	u32 packetlen;
 	u32 packetlen_aligned;
 	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
-	bool signal = false;
 	bool lock = channel->acquire_ring_lock;
 	u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset,
 					 multi_pagebuffer->len);
@@ -930,13 +856,8 @@ int vmbus_sendpacket_multipagebuffer(struct vmbus_channel *channel,
 	bufferlist[2].iov_base = &aligned_data;
 	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
-	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3,
-				  &signal, lock, channel->signal_policy);
-
-	if (ret == 0 && signal)
-		vmbus_setevent(channel);
-
-	return ret;
+	return hv_ringbuffer_write(channel, bufferlist, 3,
+				   lock, true);
 }
 EXPORT_SYMBOL_GPL(vmbus_sendpacket_multipagebuffer);