1 files changed, 316 insertions, 0 deletions
diff --git a/tools/virtio/ringtest/virtio_ring_0_9.c b/tools/virtio/ringtest/virtio_ring_0_9.c
new file mode 100644
index 000000000000..47c9a1a18d36
--- /dev/null
+++ b/tools/virtio/ringtest/virtio_ring_0_9.c
@@ -0,0 +1,316 @@
+/*
+ * Copyright (C) 2016 Red Hat, Inc.
+ * Author: Michael S. Tsirkin <mst@redhat.com>
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * Partial implementation of virtio 0.9. event index is used for signalling,
+ * unconditionally. Design roughly follows linux kernel implementation in order
+ * to be able to judge its performance.
+ */
+#define _GNU_SOURCE
+#include "main.h"
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+#include <linux/virtio_ring.h>
+
+struct data {
+	void *data;
+} *data;
+
+struct vring ring;
+
+/* enabling the below activates experimental ring polling code
+ * (which skips index reads on consumer in favor of looking at
+ * high bits of ring id ^ 0x8000).
+ */
+/* #ifdef RING_POLL */
+
+/* how much padding is needed to avoid false cache sharing */
+#define HOST_GUEST_PADDING 0x80
+
+struct guest {
+	unsigned short avail_idx;
+	unsigned short last_used_idx;
+	unsigned short num_free;
+	unsigned short kicked_avail_idx;
+	unsigned short free_head;
+	unsigned char reserved[HOST_GUEST_PADDING - 10];
+} guest;
+
+struct host {
+	/* we do not need to track last avail index
+	 * unless we have more than one in flight.
+	 */
+	unsigned short used_idx;
+	unsigned short called_used_idx;
+	unsigned char reserved[HOST_GUEST_PADDING - 4];
+} host;
+
+/* implemented by ring */
+void alloc_ring(void)
+{
+	int ret;
+	int i;
+	void *p;
+
+	ret = posix_memalign(&p, 0x1000, vring_size(ring_size, 0x1000));
+	if (ret) {
+		perror("Unable to allocate ring buffer.\n");
+		exit(3);
+	}
+	memset(p, 0, vring_size(ring_size, 0x1000));
+	vring_init(&ring, ring_size, p, 0x1000);
+
+	guest.avail_idx = 0;
+	guest.kicked_avail_idx = -1;
+	guest.last_used_idx = 0;
+	/* Put everything in free lists. */
+	guest.free_head = 0;
+	for (i = 0; i < ring_size - 1; i++)
+		ring.desc[i].next = i + 1;
+	host.used_idx = 0;
+	host.called_used_idx = -1;
+	guest.num_free = ring_size;
+	data = malloc(ring_size * sizeof *data);
+	if (!data) {
+		perror("Unable to allocate data buffer.\n");
+		exit(3);
+	}
+	memset(data, 0, ring_size * sizeof *data);
+}
+
+/* guest side */
+int add_inbuf(unsigned len, void *buf, void *datap)
+{
+	unsigned head, avail;
+	struct vring_desc *desc;
+
+	if (!guest.num_free)
+		return -1;
+
+	head = guest.free_head;
+	guest.num_free--;
+
+	desc = ring.desc;
+	desc[head].flags = VRING_DESC_F_NEXT;
+	desc[head].addr = (unsigned long)(void *)buf;
+	desc[head].len = len;
+	/* We do it like this to simulate the way
+	 * we'd have to flip it if we had multiple
+	 * descriptors.
+	 */
+	desc[head].flags &= ~VRING_DESC_F_NEXT;
+	guest.free_head = desc[head].next;
+
+	data[head].data = datap;
+
+#ifdef RING_POLL
+	/* Barrier A (for pairing) */
+	smp_release();
+	avail = guest.avail_idx++;
+	ring.avail->ring[avail & (ring_size - 1)] =
+		(head | (avail & ~(ring_size - 1))) ^ 0x8000;
+#else
+	avail = (ring_size - 1) & (guest.avail_idx++);
+	ring.avail->ring[avail] = head;
+	/* Barrier A (for pairing) */
+	smp_release();
+#endif
+	ring.avail->idx = guest.avail_idx;
+	return 0;
+}
+
+void *get_buf(unsigned *lenp, void **bufp)
+{
+	unsigned head;
+	unsigned index;
+	void *datap;
+
+#ifdef RING_POLL
+	head = (ring_size - 1) & guest.last_used_idx;
+	index = ring.used->ring[head].id;
+	if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1))
+		return NULL;
+	/* Barrier B (for pairing) */
+	smp_acquire();
+	index &= ring_size - 1;
+#else
+	if (ring.used->idx == guest.last_used_idx)
+		return NULL;
+	/* Barrier B (for pairing) */
+	smp_acquire();
+	head = (ring_size - 1) & guest.last_used_idx;
+	index = ring.used->ring[head].id;
+#endif
+	*lenp = ring.used->ring[head].len;
+	datap = data[index].data;
+	*bufp = (void*)(unsigned long)ring.desc[index].addr;
+	data[index].data = NULL;
+	ring.desc[index].next = guest.free_head;
+	guest.free_head = index;
+	guest.num_free++;
+	guest.last_used_idx++;
+	return datap;
+}
+
+void poll_used(void)
+{
+#ifdef RING_POLL
+	unsigned head = (ring_size - 1) & guest.last_used_idx;
+
+	for (;;) {
+		unsigned index = ring.used->ring[head].id;
+
+		if ((index ^ guest.last_used_idx ^ 0x8000) & ~(ring_size - 1))
+			busy_wait();
+		else
+			break;
+	}
+#else
+	unsigned head = guest.last_used_idx;
+
+	while (ring.used->idx == head)
+		busy_wait();
+#endif
+}
+
+void disable_call()
+{
+	/* Doing nothing to disable calls might cause
+	 * extra interrupts, but reduces the number of cache misses.
+	 */
+}
+
+bool enable_call()
+{
+	unsigned short last_used_idx;
+
+	vring_used_event(&ring) = (last_used_idx = 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
+}
+
+void kick_available(void)
+{
+	/* Flush in previous flags write */
+	/* Barrier C (for pairing) */
+	smp_mb();
+	if (!vring_need_event(vring_avail_event(&ring),
+			      guest.avail_idx,
+			      guest.kicked_avail_idx))
+		return;
+
+	guest.kicked_avail_idx = guest.avail_idx;
+	kick();
+}
+
+/* host side */
+void disable_kick()
+{
+	/* Doing nothing to disable kicks might cause
+	 * extra interrupts, but reduces the number of cache misses.
+	 */
+}
+
+bool enable_kick()
+{
+	unsigned head = host.used_idx;
+
+	vring_avail_event(&ring) = head;
+	/* 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
+}
+
+void poll_avail(void)
+{
+	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;
+	}
+#else
+	while (ring.avail->idx == head)
+		busy_wait();
+#endif
+}
+
+bool use_buf(unsigned *lenp, void **bufp)
+{
+	unsigned used_idx = host.used_idx;
+	struct vring_desc *desc;
+	unsigned head;
+
+#ifdef RING_POLL
+	head = ring.avail->ring[used_idx & (ring_size - 1)];
+	if ((used_idx ^ head ^ 0x8000) & ~(ring_size - 1))
+		return false;
+	/* Barrier A (for pairing) */
+	smp_acquire();
+
+	used_idx &= ring_size - 1;
+	desc = &ring.desc[head & (ring_size - 1)];
+#else
+	if (used_idx == ring.avail->idx)
+		return false;
+
+	/* Barrier A (for pairing) */
+	smp_acquire();
+
+	used_idx &= ring_size - 1;
+	head = ring.avail->ring[used_idx];
+	desc = &ring.desc[head];
+#endif
+
+	*lenp = desc->len;
+	*bufp = (void *)(unsigned long)desc->addr;
+
+	/* now update used ring */
+	ring.used->ring[used_idx].id = head;
+	ring.used->ring[used_idx].len = desc->len - 1;
+	/* Barrier B (for pairing) */
+	smp_release();
+	host.used_idx++;
+	ring.used->idx = host.used_idx;
+	
+	return true;
+}
+
+void call_used(void)
+{
+	/* Flush in previous flags write */
+	/* Barrier D (for pairing) */
+	smp_mb();
+	if (!vring_need_event(vring_used_event(&ring),
+			      host.used_idx,
+			      host.called_used_idx))
+		return;
+
+	host.called_used_idx = host.used_idx;
+	call();
+}