vmbus: use kernel bitops for traversing interrupt mask

Use standard kernel operations for find first set bit to traverse
the channel bit array. This has added benefit of speeding up
lookup on 64 bit and because it uses find first set instruction.

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

drivers/hv/channel.c

@@ -47,12 +47,8 @@ void vmbus_setevent(struct vmbus_channel *channel)
 	 * For channels marked as in "low latency" mode
 	 * bypass the monitor page mechanism.
 	 */
-	if ((channel->offermsg.monitor_allocated) &&
-	    (!channel->low_latency)) {
-		/* Each u32 represents 32 channels */
-		sync_set_bit(channel->offermsg.child_relid & 31,
-			(unsigned long *) vmbus_connection.send_int_page +
-			(channel->offermsg.child_relid >> 5));
+	if (channel->offermsg.monitor_allocated && !channel->low_latency) {
+		vmbus_send_interrupt(channel->offermsg.child_relid);
 
 		/* Get the child to parent monitor page */
 		monitorpage = vmbus_connection.monitor_pages[1];

drivers/hv/connection.c

@@ -379,17 +379,11 @@ static void process_chn_event(u32 relid)
  */
 void vmbus_on_event(unsigned long data)
 {
-	u32 dword;
-	u32 maxdword;
-	int bit;
-	u32 relid;
-	u32 *recv_int_page = NULL;
-	void *page_addr;
-	int cpu = smp_processor_id();
-	union hv_synic_event_flags *event;
+	unsigned long *recv_int_page;
+	u32 maxbits, relid;
 
 	if (vmbus_proto_version < VERSION_WIN8) {
-		maxdword = MAX_NUM_CHANNELS_SUPPORTED >> 5;
+		maxbits = MAX_NUM_CHANNELS_SUPPORTED;
 		recv_int_page = vmbus_connection.recv_int_page;
 	} else {
 		/*
@@ -397,35 +391,24 @@ void vmbus_on_event(unsigned long data)
 		 * can be directly checked to get the id of the channel
 		 * that has the interrupt pending.
 		 */
-		maxdword = HV_EVENT_FLAGS_DWORD_COUNT;
-		page_addr = hv_context.synic_event_page[cpu];
-		event = (union hv_synic_event_flags *)page_addr +
+		int cpu = smp_processor_id();
+		void *page_addr = hv_context.synic_event_page[cpu];
+		union hv_synic_event_flags *event
+			= (union hv_synic_event_flags *)page_addr +
 						 VMBUS_MESSAGE_SINT;
-		recv_int_page = event->flags32;
-	}
-
 
+		maxbits = HV_EVENT_FLAGS_COUNT;
+		recv_int_page = event->flags;
+	}
 
-	/* Check events */
-	if (!recv_int_page)
+	if (unlikely(!recv_int_page))
 		return;
-	for (dword = 0; dword < maxdword; dword++) {
-		if (!recv_int_page[dword])
-			continue;
-		for (bit = 0; bit < 32; bit++) {
-			if (sync_test_and_clear_bit(bit,
-				(unsigned long *)&recv_int_page[dword])) {
-				relid = (dword << 5) + bit;
-
-				if (relid == 0)
-					/*
-					 * Special case - vmbus
-					 * channel protocol msg
-					 */
-					continue;
 
+	for_each_set_bit(relid, recv_int_page, maxbits) {
+		if (sync_test_and_clear_bit(relid, recv_int_page)) {
+			/* Special case - vmbus channel protocol msg */
+			if (relid != 0)
 				process_chn_event(relid);
-			}
 		}
 	}
 }
@@ -491,12 +474,8 @@ void vmbus_set_event(struct vmbus_channel *channel)
 {
 	u32 child_relid = channel->offermsg.child_relid;
 
-	if (!channel->is_dedicated_interrupt) {
-		/* Each u32 represents 32 channels */
-		sync_set_bit(child_relid & 31,
-			(unsigned long *)vmbus_connection.send_int_page +
-			(child_relid >> 5));
-	}
+	if (!channel->is_dedicated_interrupt)
+		vmbus_send_interrupt(child_relid);
 
 	hv_do_hypercall(HVCALL_SIGNAL_EVENT, channel->sig_event, NULL);
 }

drivers/hv/hyperv_vmbus.h

@@ -40,11 +40,9 @@
  */
 #define HV_UTIL_NEGO_TIMEOUT 55
 
-
-
-
-#define HV_EVENT_FLAGS_BYTE_COUNT	(256)
-#define HV_EVENT_FLAGS_DWORD_COUNT	(256 / sizeof(u32))
+/* Define synthetic interrupt controller flag constants. */
+#define HV_EVENT_FLAGS_COUNT		(256 * 8)
+#define HV_EVENT_FLAGS_LONG_COUNT	(256 / sizeof(unsigned long))
 
 /*
  * Timer configuration register.
@@ -65,8 +63,7 @@ union hv_timer_config {
 
 /* Define the synthetic interrupt controller event flags format. */
 union hv_synic_event_flags {
-	u8 flags8[HV_EVENT_FLAGS_BYTE_COUNT];
-	u32 flags32[HV_EVENT_FLAGS_DWORD_COUNT];
+	unsigned long flags[HV_EVENT_FLAGS_LONG_COUNT];
 };
 
 /* Define SynIC control register. */
@@ -358,6 +355,11 @@ struct vmbus_msginfo {
 
 extern struct vmbus_connection vmbus_connection;
 
+static inline void vmbus_send_interrupt(u32 relid)
+{
+	sync_set_bit(relid, vmbus_connection.send_int_page);
+}
+
 enum vmbus_message_handler_type {
 	/* The related handler can sleep. */
 	VMHT_BLOCKING = 0,

drivers/hv/vmbus_drv.c

@@ -908,10 +908,8 @@ static void vmbus_isr(void)
 		(vmbus_proto_version == VERSION_WIN7)) {
 
 		/* Since we are a child, we only need to check bit 0 */
-		if (sync_test_and_clear_bit(0,
-			(unsigned long *) &event->flags32[0])) {
+		if (sync_test_and_clear_bit(0, event->flags))
 			handled = true;
-		}
 	} else {
 		/*
 		 * Our host is win8 or above. The signaling mechanism