ringtest: commonize implementation of poll_avail/poll_used

Provide new primitives used_empty/avail_empty and
build poll_avail/poll_used on top of it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/virtio/ringtest/main.c

@@ -96,6 +96,12 @@ void set_affinity(const char *arg)
 	assert(!ret);
 }
 
+void poll_used(void)
+{
+	while (used_empty())
+		busy_wait();
+}
+
 static void __attribute__((__flatten__)) run_guest(void)
 {
 	int completed_before;
@@ -149,6 +155,12 @@ static void __attribute__((__flatten__)) run_guest(void)
 	}
 }
 
+void poll_avail(void)
+{
+	while (avail_empty())
+		busy_wait();
+}
+
 static void __attribute__((__flatten__)) run_host(void)
 {
 	int completed_before;

tools/virtio/ringtest/main.h

@@ -56,15 +56,15 @@ void alloc_ring(void);
 int add_inbuf(unsigned, void *, void *);
 void *get_buf(unsigned *, void **);
 void disable_call();
+bool used_empty();
 bool enable_call();
 void kick_available();
-void poll_used();
 /* host side */
 void disable_kick();
+bool avail_empty();
 bool enable_kick();
 bool use_buf(unsigned *, void **);
 void call_used();
-void poll_avail();
 
 /* implemented by main */
 extern bool do_sleep;

tools/virtio/ringtest/noring.c

@@ -24,8 +24,9 @@ void *get_buf(unsigned *lenp, void **bufp)
 	return "Buffer";
 }
 
-void poll_used(void)
+bool used_empty()
 {
+	return false;
 }
 
 void disable_call()
@@ -54,8 +55,9 @@ bool enable_kick()
 	assert(0);
 }
 
-void poll_avail(void)
+bool avail_empty()
 {
+	return false;
 }
 
 bool use_buf(unsigned *lenp, void **bufp)

tools/virtio/ringtest/ptr_ring.c

@@ -133,18 +133,9 @@ void *get_buf(unsigned *lenp, void **bufp)
 	return datap;
 }
 
-void poll_used(void)
+bool used_empty()
 {
-	void *b;
-
-	do {
-		if (tailcnt == headcnt || __ptr_ring_full(&array)) {
-			b = NULL;
-			barrier();
-		} else {
-			b = "Buffer\n";
-		}
-	} while (!b);
+	return (tailcnt == headcnt || __ptr_ring_full(&array));
 }
 
 void disable_call()
@@ -173,14 +164,9 @@ bool enable_kick()
 	assert(0);
 }
 
-void poll_avail(void)
+bool avail_empty()
 {
-	void *b;
-
-	do {
-		barrier();
-		b = __ptr_ring_peek(&array);
-	} while (!b);
+	return !__ptr_ring_peek(&array);
 }
 
 bool use_buf(unsigned *lenp, void **bufp)

tools/virtio/ringtest/ring.c

@@ -163,12 +163,11 @@ void *get_buf(unsigned *lenp, void **bufp)
 	return datap;
 }
 
-void poll_used(void)
+bool used_empty()
 {
 	unsigned head = (ring_size - 1) & guest.last_used_idx;
 
-	while (ring[head].flags & DESC_HW)
-		busy_wait();
+	return (ring[head].flags & DESC_HW);
 }
 
 void disable_call()
@@ -180,13 +179,11 @@ void disable_call()
 
 bool enable_call()
 {
-	unsigned head = (ring_size - 1) & guest.last_used_idx;
-
 	event->call_index = guest.last_used_idx;
 	/* Flush call index write */
 	/* Barrier D (for pairing) */
 	smp_mb();
-	return ring[head].flags & DESC_HW;
+	return used_empty();
 }
 
 void kick_available(void)
@@ -213,20 +210,17 @@ void disable_kick()
 
 bool enable_kick()
 {
-	unsigned head = (ring_size - 1) & host.used_idx;
-
 	event->kick_index = host.used_idx;
 	/* Barrier C (for pairing) */
 	smp_mb();
-	return !(ring[head].flags & DESC_HW);
+	return avail_empty();
 }
 
-void poll_avail(void)
+bool avail_empty()
 {
 	unsigned head = (ring_size - 1) & host.used_idx;
 
-	while (!(ring[head].flags & DESC_HW))
-		busy_wait();
+	return !(ring[head].flags & DESC_HW);
 }
 
 bool use_buf(unsigned *lenp, void **bufp)

tools/virtio/ringtest/virtio_ring_0_9.c

@@ -194,24 +194,16 @@ void *get_buf(unsigned *lenp, void **bufp)
 	return datap;
 }
 
-void poll_used(void)
+bool used_empty()
 {
+	unsigned short last_used_idx = guest.last_used_idx;
 #ifdef RING_POLL
-	unsigned head = (ring_size - 1) & guest.last_used_idx;
-
-	for (;;) {
+	unsigned short head = last_used_idx & (ring_size - 1);
 	unsigned index = ring.used->ring[head].id;
 
-		if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1))
-			busy_wait();
-		else
-			break;
-	}
+	return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1);
 #else
-	unsigned head = guest.last_used_idx;
-
-	while (ring.used->idx == head)
-		busy_wait();
+	return ring.used->idx == last_used_idx;
 #endif
 }
 
@@ -224,22 +216,11 @@ void disable_call()
 
 bool enable_call()
 {
-	unsigned short last_used_idx;
-
-	vring_used_event(&ring) = (last_used_idx = guest.last_used_idx);
+	vring_used_event(&ring) = guest.last_used_idx;
 	/* Flush call index write */
 	/* Barrier D (for pairing) */
 	smp_mb();
-#ifdef RING_POLL
-	{
-		unsigned short head = last_used_idx & (ring_size - 1);
-		unsigned index = ring.used->ring[head].id;
-
-		return (index ^ last_used_idx ^ 0x8000) & ~(ring_size - 1);
-	}
-#else
-	return ring.used->idx == last_used_idx;
-#endif
+	return used_empty();
 }
 
 void kick_available(void)
@@ -266,36 +247,21 @@ void disable_kick()
 
 bool enable_kick()
 {
-	unsigned head = host.used_idx;
-
-	vring_avail_event(&ring) = head;
+	vring_avail_event(&ring) = host.used_idx;
 	/* Barrier C (for pairing) */
 	smp_mb();
-#ifdef RING_POLL
-	{
-		unsigned index = ring.avail->ring[head & (ring_size - 1)];
-
-		return (index ^ head ^ 0x8000) & ~(ring_size - 1);
-	}
-#else
-	return head == ring.avail->idx;
-#endif
+	return avail_empty();
 }
 
-void poll_avail(void)
+bool avail_empty()
 {
 	unsigned head = host.used_idx;
 #ifdef RING_POLL
-	for (;;) {
 	unsigned index = ring.avail->ring[head & (ring_size - 1)];
-		if ((index ^ head ^ 0x8000) & ~(ring_size - 1))
-			busy_wait();
-		else
-			break;
-	}
+
+	return ((index ^ head ^ 0x8000) & ~(ring_size - 1));
 #else
-	while (ring.avail->idx == head)
-		busy_wait();
+	return head == ring.avail->idx;
 #endif
 }