tools/virtio: add vring_test.

This is mainly to test the drivers/vhost/vringh.c code, but it also
uses the drivers/virtio/virtio_ring.c code for the guest side.

Usage for testing the basic implementation:

	./vringh_test
	# Test with indirect descriptors
	./vringh_test --indirect
	# Test with indirect descriptors and event indexex
	./vringh_test --indirect --eventidx

You can run a parallel stress test by adding --parallel to any of the
above options.

eg ./vringh_test --parallel:
	Using CPUS 0 and 3
	Guest: notified 10107974, pinged 107970
	Host: notified 108158, pinged 3172148

./vringh_test --indirect --eventidx --parallel:
	Using CPUS 0 and 3
	Guest: notified 156357, pinged 156251
	Host: notified 156251, pinged 78179

Average of 50 times doing ./vringh_test --indirect --eventidx --parallel:
	2.840000-3.040000(2.927292)user

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

3 files changed, 747 insertions, 4 deletions

diff --git a/tools/virtio/Makefile b/tools/virtio/Makefile
index b48c4329e644..3187c62d9814 100644
--- a/tools/virtio/Makefile
+++ b/tools/virtio/Makefile
@@ -1,12 +1,14 @@
 all: test mod
-test: virtio_test
+test: virtio_test vringh_test
 virtio_test: virtio_ring.o virtio_test.o
-CFLAGS += -g -O2 -Wall -I. -I ../../usr/include/ -Wno-pointer-sign -fno-strict-overflow -fno-strict-aliasing -fno-common -MMD
-vpath %.c ../../drivers/virtio
+vringh_test: vringh_test.o vringh.o virtio_ring.o
+
+CFLAGS += -g -O2 -Wall -I. -I ../../usr/include/ -Wno-pointer-sign -fno-strict-overflow -fno-strict-aliasing -fno-common -MMD -U_FORTIFY_SOURCE
+vpath %.c ../../drivers/virtio ../../drivers/vhost
 mod:
         ${MAKE} -C `pwd`/../.. M=`pwd`/vhost_test
 .PHONY: all test mod clean
 clean:
-        ${RM} *.o vhost_test/*.o vhost_test/.*.cmd \
+        ${RM} *.o vringh_test virtio_test vhost_test/*.o vhost_test/.*.cmd \
               vhost_test/Module.symvers vhost_test/modules.order *.d
 -include *.d
diff --git a/tools/virtio/linux/uio.h b/tools/virtio/linux/uio.h
index ecbdf922b0f4..cd20f0ba3081 100644
--- a/tools/virtio/linux/uio.h
+++ b/tools/virtio/linux/uio.h
@@ -1 +1,3 @@
+#include <linux/kernel.h>
+
 #include "../../../include/linux/uio.h"
diff --git a/tools/virtio/vringh_test.c b/tools/virtio/vringh_test.c
new file mode 100644
index 000000000000..6a48ca5c101f
--- /dev/null
+++ b/tools/virtio/vringh_test.c
@@ -0,0 +1,739 @@
+/* Simple test of virtio code, entirely in userpsace. */
+#define _GNU_SOURCE
+#include <sched.h>
+#include <err.h>
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <linux/virtio.h>
+#include <linux/vringh.h>
+#include <linux/virtio_ring.h>
+#include <linux/uaccess.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/mman.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+
+#define USER_MEM (1024*1024)
+void *__user_addr_min, *__user_addr_max;
+void *__kmalloc_fake, *__kfree_ignore_start, *__kfree_ignore_end;
+static u64 user_addr_offset;
+
+#define RINGSIZE 256
+#define ALIGN 4096
+
+static void never_notify_host(struct virtqueue *vq)
+{
+        abort();
+}
+
+static void never_callback_guest(struct virtqueue *vq)
+{
+        abort();
+}
+
+static bool getrange_iov(struct vringh *vrh, u64 addr, struct vringh_range *r)
+{
+        if (addr < (u64)(unsigned long)__user_addr_min - user_addr_offset)
+                return false;
+        if (addr >= (u64)(unsigned long)__user_addr_max - user_addr_offset)
+                return false;
+
+        r->start = (u64)(unsigned long)__user_addr_min - user_addr_offset;
+        r->end_incl = (u64)(unsigned long)__user_addr_max - 1 - user_addr_offset;
+        r->offset = user_addr_offset;
+        return true;
+}
+
+/* We return single byte ranges. */
+static bool getrange_slow(struct vringh *vrh, u64 addr, struct vringh_range *r)
+{
+        if (addr < (u64)(unsigned long)__user_addr_min - user_addr_offset)
+                return false;
+        if (addr >= (u64)(unsigned long)__user_addr_max - user_addr_offset)
+                return false;
+
+        r->start = addr;
+        r->end_incl = r->start;
+        r->offset = user_addr_offset;
+        return true;
+}
+
+struct guest_virtio_device {
+        struct virtio_device vdev;
+        int to_host_fd;
+        unsigned long notifies;
+};
+
+static void parallel_notify_host(struct virtqueue *vq)
+{
+        struct guest_virtio_device *gvdev;
+
+        gvdev = container_of(vq->vdev, struct guest_virtio_device, vdev);
+        write(gvdev->to_host_fd, "", 1);
+        gvdev->notifies++;
+}
+
+static void no_notify_host(struct virtqueue *vq)
+{
+}
+
+#define NUM_XFERS (10000000)
+
+/* We aim for two "distant" cpus. */
+static void find_cpus(unsigned int *first, unsigned int *last)
+{
+        unsigned int i;
+
+        *first = -1U;
+        *last = 0;
+        for (i = 0; i < 4096; i++) {
+                cpu_set_t set;
+                CPU_ZERO(&set);
+                CPU_SET(i, &set);
+                if (sched_setaffinity(getpid(), sizeof(set), &set) == 0) {
+                        if (i < *first)
+                                *first = i;
+                        if (i > *last)
+                                *last = i;
+                }
+        }
+}
+
+/* Opencoded version for fast mode */
+static inline int vringh_get_head(struct vringh *vrh, u16 *head)
+{
+        u16 avail_idx, i;
+        int err;
+
+        err = get_user(avail_idx, &vrh->vring.avail->idx);
+        if (err)
+                return err;
+
+        if (vrh->last_avail_idx == avail_idx)
+                return 0;
+
+        /* Only get avail ring entries after they have been exposed by guest. */
+        virtio_rmb(vrh->weak_barriers);
+
+        i = vrh->last_avail_idx & (vrh->vring.num - 1);
+
+        err = get_user(*head, &vrh->vring.avail->ring[i]);
+        if (err)
+                return err;
+
+        vrh->last_avail_idx++;
+        return 1;
+}
+
+static int parallel_test(unsigned long features,
+                         bool (*getrange)(struct vringh *vrh,
+                                          u64 addr, struct vringh_range *r),
+                         bool fast_vringh)
+{
+        void *host_map, *guest_map;
+        int fd, mapsize, to_guest[2], to_host[2];
+        unsigned long xfers = 0, notifies = 0, receives = 0;
+        unsigned int first_cpu, last_cpu;
+        cpu_set_t cpu_set;
+        char buf[128];
+
+        /* Create real file to mmap. */
+        fd = open("/tmp/vringh_test-file", O_RDWR|O_CREAT|O_TRUNC, 0600);
+        if (fd < 0)
+                err(1, "Opening /tmp/vringh_test-file");
+
+        /* Extra room at the end for some data, and indirects */
+        mapsize = vring_size(RINGSIZE, ALIGN)
+                + RINGSIZE * 2 * sizeof(int)
+                + RINGSIZE * 6 * sizeof(struct vring_desc);
+        mapsize = (mapsize + getpagesize() - 1) & ~(getpagesize() - 1);
+        ftruncate(fd, mapsize);
+
+        /* Parent and child use separate addresses, to check our mapping logic! */
+        host_map = mmap(NULL, mapsize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+        guest_map = mmap(NULL, mapsize, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+
+        pipe(to_guest);
+        pipe(to_host);
+
+        CPU_ZERO(&cpu_set);
+        find_cpus(&first_cpu, &last_cpu);
+        printf("Using CPUS %u and %u\n", first_cpu, last_cpu);
+        fflush(stdout);
+
+        if (fork() != 0) {
+                struct vringh vrh;
+                int status, err, rlen = 0;
+                char rbuf[5];
+
+                /* We are the host: never access guest addresses! */
+                munmap(guest_map, mapsize);
+
+                __user_addr_min = host_map;
+                __user_addr_max = __user_addr_min + mapsize;
+                user_addr_offset = host_map - guest_map;
+                assert(user_addr_offset);
+
+                close(to_guest[0]);
+                close(to_host[1]);
+
+                vring_init(&vrh.vring, RINGSIZE, host_map, ALIGN);
+                vringh_init_user(&vrh, features, RINGSIZE, true,
+                                 vrh.vring.desc, vrh.vring.avail, vrh.vring.used);
+                CPU_SET(first_cpu, &cpu_set);
+                if (sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set))
+                        errx(1, "Could not set affinity to cpu %u", first_cpu);
+
+                while (xfers < NUM_XFERS) {
+                        struct iovec host_riov[2], host_wiov[2];
+                        struct vringh_iov riov, wiov;
+                        u16 head, written;
+
+                        if (fast_vringh) {
+                                for (;;) {
+                                        err = vringh_get_head(&vrh, &head);
+                                        if (err != 0)
+                                                break;
+                                        err = vringh_need_notify_user(&vrh);
+                                        if (err < 0)
+                                                errx(1, "vringh_need_notify_user: %i",
+                                                     err);
+                                        if (err) {
+                                                write(to_guest[1], "", 1);
+                                                notifies++;
+                                        }
+                                }
+                                if (err != 1)
+                                        errx(1, "vringh_get_head");
+                                written = 0;
+                                goto complete;
+                        } else {
+                                vringh_iov_init(&riov,
+                                                host_riov,
+                                                ARRAY_SIZE(host_riov));
+                                vringh_iov_init(&wiov,
+                                                host_wiov,
+                                                ARRAY_SIZE(host_wiov));
+
+                                err = vringh_getdesc_user(&vrh, &riov, &wiov,
+                                                          getrange, &head);
+                        }
+                        if (err == 0) {
+                                err = vringh_need_notify_user(&vrh);
+                                if (err < 0)
+                                        errx(1, "vringh_need_notify_user: %i",
+                                             err);
+                                if (err) {
+                                        write(to_guest[1], "", 1);
+                                        notifies++;
+                                }
+
+                                if (!vringh_notify_enable_user(&vrh))
+                                        continue;
+
+                                /* Swallow all notifies at once. */
+                                if (read(to_host[0], buf, sizeof(buf)) < 1)
+                                        break;
+
+                                vringh_notify_disable_user(&vrh);
+                                receives++;
+                                continue;
+                        }
+                        if (err != 1)
+                                errx(1, "vringh_getdesc_user: %i", err);
+
+                        /* We simply copy bytes. */
+                        if (riov.used) {
+                                rlen = vringh_iov_pull_user(&riov, rbuf,
+                                                            sizeof(rbuf));
+                                if (rlen != 4)
+                                        errx(1, "vringh_iov_pull_user: %i",
+                                             rlen);
+                                assert(riov.i == riov.used);
+                                written = 0;
+                        } else {
+                                err = vringh_iov_push_user(&wiov, rbuf, rlen);
+                                if (err != rlen)
+                                        errx(1, "vringh_iov_push_user: %i",
+                                             err);
+                                assert(wiov.i == wiov.used);
+                                written = err;
+                        }
+                complete:
+                        xfers++;
+
+                        err = vringh_complete_user(&vrh, head, written);
+                        if (err != 0)
+                                errx(1, "vringh_complete_user: %i", err);
+                }
+
+                err = vringh_need_notify_user(&vrh);
+                if (err < 0)
+                        errx(1, "vringh_need_notify_user: %i", err);
+                if (err) {
+                        write(to_guest[1], "", 1);
+                        notifies++;
+                }
+                wait(&status);
+                if (!WIFEXITED(status))
+                        errx(1, "Child died with signal %i?", WTERMSIG(status));
+                if (WEXITSTATUS(status) != 0)
+                        errx(1, "Child exited %i?", WEXITSTATUS(status));
+                printf("Host: notified %lu, pinged %lu\n", notifies, receives);
+                return 0;
+        } else {
+                struct guest_virtio_device gvdev;
+                struct virtqueue *vq;
+                unsigned int *data;
+                struct vring_desc *indirects;
+                unsigned int finished = 0;
+
+                /* We pass sg[]s pointing into here, but we need RINGSIZE+1 */
+                data = guest_map + vring_size(RINGSIZE, ALIGN);
+                indirects = (void *)data + (RINGSIZE + 1) * 2 * sizeof(int);
+
+                /* We are the guest. */
+                munmap(host_map, mapsize);
+
+                close(to_guest[1]);
+                close(to_host[0]);
+
+                gvdev.vdev.features[0] = features;
+                gvdev.to_host_fd = to_host[1];
+                gvdev.notifies = 0;
+
+                CPU_SET(first_cpu, &cpu_set);
+                if (sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set))
+                        err(1, "Could not set affinity to cpu %u", first_cpu);
+
+                vq = vring_new_virtqueue(0, RINGSIZE, ALIGN, &gvdev.vdev, true,
+                                         guest_map, fast_vringh ? no_notify_host
+                                         : parallel_notify_host,
+                                         never_callback_guest, "guest vq");
+
+                /* Don't kfree indirects. */
+                __kfree_ignore_start = indirects;
+                __kfree_ignore_end = indirects + RINGSIZE * 6;
+
+                while (xfers < NUM_XFERS) {
+                        struct scatterlist sg[4];
+                        unsigned int num_sg, len;
+                        int *dbuf, err;
+                        bool output = !(xfers % 2);
+
+                        /* Consume bufs. */
+                        while ((dbuf = virtqueue_get_buf(vq, &len)) != NULL) {
+                                if (len == 4)
+                                        assert(*dbuf == finished - 1);
+                                else if (!fast_vringh)
+                                        assert(*dbuf == finished);
+                                finished++;
+                        }
+
+                        /* Produce a buffer. */
+                        dbuf = data + (xfers % (RINGSIZE + 1));
+
+                        if (output)
+                                *dbuf = xfers;
+                        else
+                                *dbuf = -1;
+
+                        switch ((xfers / sizeof(*dbuf)) % 4) {
+                        case 0:
+                                /* Nasty three-element sg list. */
+                                sg_init_table(sg, num_sg = 3);
+                                sg_set_buf(&sg[0], (void *)dbuf, 1);
+                                sg_set_buf(&sg[1], (void *)dbuf + 1, 2);
+                                sg_set_buf(&sg[2], (void *)dbuf + 3, 1);
+                                break;
+                        case 1:
+                                sg_init_table(sg, num_sg = 2);
+                                sg_set_buf(&sg[0], (void *)dbuf, 1);
+                                sg_set_buf(&sg[1], (void *)dbuf + 1, 3);
+                                break;
+                        case 2:
+                                sg_init_table(sg, num_sg = 1);
+                                sg_set_buf(&sg[0], (void *)dbuf, 4);
+                                break;
+                        case 3:
+                                sg_init_table(sg, num_sg = 4);
+                                sg_set_buf(&sg[0], (void *)dbuf, 1);
+                                sg_set_buf(&sg[1], (void *)dbuf + 1, 1);
+                                sg_set_buf(&sg[2], (void *)dbuf + 2, 1);
+                                sg_set_buf(&sg[3], (void *)dbuf + 3, 1);
+                                break;
+                        }
+
+                        /* May allocate an indirect, so force it to allocate
+                         * user addr */
+                        __kmalloc_fake = indirects + (xfers % RINGSIZE) * 4;
+                        if (output)
+                                err = virtqueue_add_buf(vq, sg, num_sg, 0, dbuf,
+                                                        GFP_KERNEL);
+                        else
+                                err = virtqueue_add_buf(vq, sg, 0, num_sg, dbuf,
+                                                        GFP_KERNEL);
+
+                        if (err == -ENOSPC) {
+                                if (!virtqueue_enable_cb_delayed(vq))
+                                        continue;
+                                /* Swallow all notifies at once. */
+                                if (read(to_guest[0], buf, sizeof(buf)) < 1)
+                                        break;
+                                
+                                receives++;
+                                virtqueue_disable_cb(vq);
+                                continue;
+                        }
+
+                        if (err)
+                                errx(1, "virtqueue_add_buf: %i", err);
+
+                        xfers++;
+                        virtqueue_kick(vq);
+                }
+
+                /* Any extra? */
+                while (finished != xfers) {
+                        int *dbuf;
+                        unsigned int len;
+
+                        /* Consume bufs. */
+                        dbuf = virtqueue_get_buf(vq, &len);
+                        if (dbuf) {
+                                if (len == 4)
+                                        assert(*dbuf == finished - 1);
+                                else
+                                        assert(len == 0);
+                                finished++;
+                                continue;
+                        }
+
+                        if (!virtqueue_enable_cb_delayed(vq))
+                                continue;
+                        if (read(to_guest[0], buf, sizeof(buf)) < 1)
+                                break;
+                                
+                        receives++;
+                        virtqueue_disable_cb(vq);
+                }
+
+                printf("Guest: notified %lu, pinged %lu\n",
+                       gvdev.notifies, receives);
+                vring_del_virtqueue(vq);
+                return 0;
+        }
+}
+
+int main(int argc, char *argv[])
+{
+        struct virtio_device vdev;
+        struct virtqueue *vq;
+        struct vringh vrh;
+        struct scatterlist guest_sg[RINGSIZE];
+        struct iovec host_riov[2], host_wiov[2];
+        struct vringh_iov riov, wiov;
+        struct vring_used_elem used[RINGSIZE];
+        char buf[28];
+        u16 head;
+        int err;
+        unsigned i;
+        void *ret;
+        bool (*getrange)(struct vringh *vrh, u64 addr, struct vringh_range *r);
+        bool fast_vringh = false, parallel = false;
+
+        getrange = getrange_iov;
+        vdev.features[0] = 0;
+
+        while (argv[1]) {
+                if (strcmp(argv[1], "--indirect") == 0)
+                        vdev.features[0] |= (1 << VIRTIO_RING_F_INDIRECT_DESC);
+                else if (strcmp(argv[1], "--eventidx") == 0)
+                        vdev.features[0] |= (1 << VIRTIO_RING_F_EVENT_IDX);
+                else if (strcmp(argv[1], "--slow-range") == 0)
+                        getrange = getrange_slow;
+                else if (strcmp(argv[1], "--fast-vringh") == 0)
+                        fast_vringh = true;
+                else if (strcmp(argv[1], "--parallel") == 0)
+                        parallel = true;
+                else
+                        errx(1, "Unknown arg %s", argv[1]);
+                argv++;
+        }
+
+        if (parallel)
+                return parallel_test(vdev.features[0], getrange, fast_vringh);
+
+        if (posix_memalign(&__user_addr_min, PAGE_SIZE, USER_MEM) != 0)
+                abort();
+        __user_addr_max = __user_addr_min + USER_MEM;
+        memset(__user_addr_min, 0, vring_size(RINGSIZE, ALIGN));
+
+        /* Set up guest side. */
+        vq = vring_new_virtqueue(0, RINGSIZE, ALIGN, &vdev, true,
+                                 __user_addr_min,
+                                 never_notify_host, never_callback_guest,
+                                 "guest vq");
+
+        /* Set up host side. */
+        vring_init(&vrh.vring, RINGSIZE, __user_addr_min, ALIGN);
+        vringh_init_user(&vrh, vdev.features[0], RINGSIZE, true,
+                         vrh.vring.desc, vrh.vring.avail, vrh.vring.used);
+
+        /* No descriptor to get yet... */
+        err = vringh_getdesc_user(&vrh, &riov, &wiov, getrange, &head);
+        if (err != 0)
+                errx(1, "vringh_getdesc_user: %i", err);
+
+        /* Guest puts in a descriptor. */
+        memcpy(__user_addr_max - 1, "a", 1);
+        sg_init_table(guest_sg, 1);
+        sg_set_buf(&guest_sg[0], __user_addr_max - 1, 1);
+        sg_init_table(guest_sg+1, 1);
+        sg_set_buf(&guest_sg[1], __user_addr_max - 3, 2);
+
+        /* May allocate an indirect, so force it to allocate user addr */
+        __kmalloc_fake = __user_addr_min + vring_size(RINGSIZE, ALIGN);
+        err = virtqueue_add_buf(vq, guest_sg, 1, 1, &err, GFP_KERNEL);
+        if (err)
+                errx(1, "virtqueue_add_buf: %i", err);
+        __kmalloc_fake = NULL;
+
+        /* Host retreives it. */
+        vringh_iov_init(&riov, host_riov, ARRAY_SIZE(host_riov));
+        vringh_iov_init(&wiov, host_wiov, ARRAY_SIZE(host_wiov));
+
+        err = vringh_getdesc_user(&vrh, &riov, &wiov, getrange, &head);
+        if (err != 1)
+                errx(1, "vringh_getdesc_user: %i", err);
+
+        assert(riov.used == 1);
+        assert(riov.iov[0].iov_base == __user_addr_max - 1);
+        assert(riov.iov[0].iov_len == 1);
+        if (getrange != getrange_slow) {
+                assert(wiov.used == 1);
+                assert(wiov.iov[0].iov_base == __user_addr_max - 3);
+                assert(wiov.iov[0].iov_len == 2);
+        } else {
+                assert(wiov.used == 2);
+                assert(wiov.iov[0].iov_base == __user_addr_max - 3);
+                assert(wiov.iov[0].iov_len == 1);
+                assert(wiov.iov[1].iov_base == __user_addr_max - 2);
+                assert(wiov.iov[1].iov_len == 1);
+        }
+
+        err = vringh_iov_pull_user(&riov, buf, 5);
+        if (err != 1)
+                errx(1, "vringh_iov_pull_user: %i", err);
+        assert(buf[0] == 'a');
+        assert(riov.i == 1);
+        assert(vringh_iov_pull_user(&riov, buf, 5) == 0);
+
+        memcpy(buf, "bcdef", 5);
+        err = vringh_iov_push_user(&wiov, buf, 5);
+        if (err != 2)
+                errx(1, "vringh_iov_push_user: %i", err);
+        assert(memcmp(__user_addr_max - 3, "bc", 2) == 0);
+        assert(wiov.i == wiov.used);
+        assert(vringh_iov_push_user(&wiov, buf, 5) == 0);
+
+        /* Host is done. */
+        err = vringh_complete_user(&vrh, head, err);
+        if (err != 0)
+                errx(1, "vringh_complete_user: %i", err);
+
+        /* Guest should see used token now. */
+        __kfree_ignore_start = __user_addr_min + vring_size(RINGSIZE, ALIGN);
+        __kfree_ignore_end = __kfree_ignore_start + 1;
+        ret = virtqueue_get_buf(vq, &i);
+        if (ret != &err)
+                errx(1, "virtqueue_get_buf: %p", ret);
+        assert(i == 2);
+
+        /* Guest puts in a huge descriptor. */
+        sg_init_table(guest_sg, RINGSIZE);
+        for (i = 0; i < RINGSIZE; i++) {
+                sg_set_buf(&guest_sg[i],
+                           __user_addr_max - USER_MEM/4, USER_MEM/4);
+        }
+
+        /* Fill contents with recognisable garbage. */
+        for (i = 0; i < USER_MEM/4; i++)
+                ((char *)__user_addr_max - USER_MEM/4)[i] = i;
+
+        /* This will allocate an indirect, so force it to allocate user addr */
+        __kmalloc_fake = __user_addr_min + vring_size(RINGSIZE, ALIGN);
+        err = virtqueue_add_buf(vq, guest_sg, RINGSIZE, 0, &err, GFP_KERNEL);
+        if (err)
+                errx(1, "virtqueue_add_buf (large): %i", err);
+        __kmalloc_fake = NULL;
+
+        /* Host picks it up (allocates new iov). */
+        vringh_iov_init(&riov, host_riov, ARRAY_SIZE(host_riov));
+        vringh_iov_init(&wiov, host_wiov, ARRAY_SIZE(host_wiov));
+
+        err = vringh_getdesc_user(&vrh, &riov, &wiov, getrange, &head);
+        if (err != 1)
+                errx(1, "vringh_getdesc_user: %i", err);
+
+        assert(riov.max_num & VRINGH_IOV_ALLOCATED);
+        assert(riov.iov != host_riov);
+        if (getrange != getrange_slow)
+                assert(riov.used == RINGSIZE);
+        else
+                assert(riov.used == RINGSIZE * USER_MEM/4);
+
+        assert(!(wiov.max_num & VRINGH_IOV_ALLOCATED));
+        assert(wiov.used == 0);
+
+        /* Pull data back out (in odd chunks), should be as expected. */
+        for (i = 0; i < RINGSIZE * USER_MEM/4; i += 3) {
+                err = vringh_iov_pull_user(&riov, buf, 3);
+                if (err != 3 && i + err != RINGSIZE * USER_MEM/4)
+                        errx(1, "vringh_iov_pull_user large: %i", err);
+                assert(buf[0] == (char)i);
+                assert(err < 2 || buf[1] == (char)(i + 1));
+                assert(err < 3 || buf[2] == (char)(i + 2));
+        }
+        assert(riov.i == riov.used);
+        vringh_iov_cleanup(&riov);
+        vringh_iov_cleanup(&wiov);
+
+        /* Complete using multi interface, just because we can. */
+        used[0].id = head;
+        used[0].len = 0;
+        err = vringh_complete_multi_user(&vrh, used, 1);
+        if (err)
+                errx(1, "vringh_complete_multi_user(1): %i", err);
+
+        /* Free up those descriptors. */
+        ret = virtqueue_get_buf(vq, &i);
+        if (ret != &err)
+                errx(1, "virtqueue_get_buf: %p", ret);
+
+        /* Add lots of descriptors. */
+        sg_init_table(guest_sg, 1);
+        sg_set_buf(&guest_sg[0], __user_addr_max - 1, 1);
+        for (i = 0; i < RINGSIZE; i++) {
+                err = virtqueue_add_buf(vq, guest_sg, 1, 0, &err, GFP_KERNEL);
+                if (err)
+                        errx(1, "virtqueue_add_buf (multiple): %i", err);
+        }
+
+        /* Now get many, and consume them all at once. */
+        vringh_iov_init(&riov, host_riov, ARRAY_SIZE(host_riov));
+        vringh_iov_init(&wiov, host_wiov, ARRAY_SIZE(host_wiov));
+
+        for (i = 0; i < RINGSIZE; i++) {
+                err = vringh_getdesc_user(&vrh, &riov, &wiov, getrange, &head);
+                if (err != 1)
+                        errx(1, "vringh_getdesc_user: %i", err);
+                used[i].id = head;
+                used[i].len = 0;
+        }
+        /* Make sure it wraps around ring, to test! */
+        assert(vrh.vring.used->idx % RINGSIZE != 0);
+        err = vringh_complete_multi_user(&vrh, used, RINGSIZE);
+        if (err)
+                errx(1, "vringh_complete_multi_user: %i", err);
+
+        /* Free those buffers. */
+        for (i = 0; i < RINGSIZE; i++) {
+                unsigned len;
+                assert(virtqueue_get_buf(vq, &len) != NULL);
+        }
+
+        /* Test weird (but legal!) indirect. */
+        if (vdev.features[0] & (1 << VIRTIO_RING_F_INDIRECT_DESC)) {
+                char *data = __user_addr_max - USER_MEM/4;
+                struct vring_desc *d = __user_addr_max - USER_MEM/2;
+                struct vring vring;
+
+                /* Force creation of direct, which we modify. */
+                vdev.features[0] &= ~(1 << VIRTIO_RING_F_INDIRECT_DESC);
+                vq = vring_new_virtqueue(0, RINGSIZE, ALIGN, &vdev, true,
+                                         __user_addr_min,
+                                         never_notify_host,
+                                         never_callback_guest,
+                                         "guest vq");
+
+                sg_init_table(guest_sg, 4);
+                sg_set_buf(&guest_sg[0], d, sizeof(*d)*2);
+                sg_set_buf(&guest_sg[1], d + 2, sizeof(*d)*1);
+                sg_set_buf(&guest_sg[2], data + 6, 4);
+                sg_set_buf(&guest_sg[3], d + 3, sizeof(*d)*3);
+
+                err = virtqueue_add_buf(vq, guest_sg, 4, 0, &err, GFP_KERNEL);
+                if (err)
+                        errx(1, "virtqueue_add_buf (indirect): %i", err);
+
+                vring_init(&vring, RINGSIZE, __user_addr_min, ALIGN);
+
+                /* They're used in order, but double-check... */
+                assert(vring.desc[0].addr == (unsigned long)d);
+                assert(vring.desc[1].addr == (unsigned long)(d+2));
+                assert(vring.desc[2].addr == (unsigned long)data + 6);
+                assert(vring.desc[3].addr == (unsigned long)(d+3));
+                vring.desc[0].flags |= VRING_DESC_F_INDIRECT;
+                vring.desc[1].flags |= VRING_DESC_F_INDIRECT;
+                vring.desc[3].flags |= VRING_DESC_F_INDIRECT;
+
+                /* First indirect */
+                d[0].addr = (unsigned long)data;
+                d[0].len = 1;
+                d[0].flags = VRING_DESC_F_NEXT;
+                d[0].next = 1;
+                d[1].addr = (unsigned long)data + 1;
+                d[1].len = 2;
+                d[1].flags = 0;
+
+                /* Second indirect */
+                d[2].addr = (unsigned long)data + 3;
+                d[2].len = 3;
+                d[2].flags = 0;
+
+                /* Third indirect */
+                d[3].addr = (unsigned long)data + 10;
+                d[3].len = 5;
+                d[3].flags = VRING_DESC_F_NEXT;
+                d[3].next = 1;
+                d[4].addr = (unsigned long)data + 15;
+                d[4].len = 6;
+                d[4].flags = VRING_DESC_F_NEXT;
+                d[4].next = 2;
+                d[5].addr = (unsigned long)data + 21;
+                d[5].len = 7;
+                d[5].flags = 0;
+
+                /* Host picks it up (allocates new iov). */
+                vringh_iov_init(&riov, host_riov, ARRAY_SIZE(host_riov));
+                vringh_iov_init(&wiov, host_wiov, ARRAY_SIZE(host_wiov));
+
+                err = vringh_getdesc_user(&vrh, &riov, &wiov, getrange, &head);
+                if (err != 1)
+                        errx(1, "vringh_getdesc_user: %i", err);
+
+                if (head != 0)
+                        errx(1, "vringh_getdesc_user: head %i not 0", head);
+
+                assert(riov.max_num & VRINGH_IOV_ALLOCATED);
+                if (getrange != getrange_slow)
+                        assert(riov.used == 7);
+                else
+                        assert(riov.used == 28);
+                err = vringh_iov_pull_user(&riov, buf, 29);
+                assert(err == 28);
+
+                /* Data should be linear. */
+                for (i = 0; i < err; i++)
+                        assert(buf[i] == i);
+                vringh_iov_cleanup(&riov);
+        }
+
+        /* Don't leak memory... */
+        vring_del_virtqueue(vq);
+        free(__user_addr_min);
+
+        return 0;
+}