// SPDX-License-Identifier: GPL-2.0
/* 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/virtio_config.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 bool 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 bool parallel_notify_host(struct virtqueue *vq)
{
        int rc;
        struct guest_virtio_device *gvdev;

        gvdev = container_of(vq->vdev, struct guest_virtio_device, vdev);
        rc = write(gvdev->to_host_fd, "", 1);
        if (rc < 0)
                return false;
        gvdev->notifies++;
        return true;
}

static bool no_notify_host(struct virtqueue *vq)
{
        return true;
}

#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(u64 features,
                         bool (*getrange)(struct vringh *vrh,
                                          u64 addr, struct vringh_range *r),
                         bool fast_vringh)
{
        void *host_map, *guest_map;
        int pipe_ret, 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_ret = pipe(to_guest);
        assert(!pipe_ret);

        pipe_ret = pipe(to_host);
        assert(!pipe_ret);

        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 = features;
                INIT_LIST_HEAD(&gvdev.vdev.vqs);
                spin_lock_init(&gvdev.vdev.vqs_list_lock);
                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,
                                         false, 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_outbuf(vq, sg, num_sg, dbuf,
                                                           GFP_KERNEL);
                        else
                                err = virtqueue_add_inbuf(vq, sg, 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_in/outbuf: %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], *sgs[2];
        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;
        INIT_LIST_HEAD(&vdev.vqs);
        spin_lock_init(&vdev.vqs_list_lock);

        while (argv[1]) {
                if (strcmp(argv[1], "--indirect") == 0)
                        __virtio_set_bit(&vdev, VIRTIO_RING_F_INDIRECT_DESC);
                else if (strcmp(argv[1], "--eventidx") == 0)
                        __virtio_set_bit(&vdev, VIRTIO_RING_F_EVENT_IDX);
                else if (strcmp(argv[1], "--virtio-1") == 0)
                        __virtio_set_bit(&vdev, VIRTIO_F_VERSION_1);
                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, 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, false,
                                 __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, 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);
        sgs[0] = &guest_sg[0];
        sgs[1] = &guest_sg[1];

        /* May allocate an indirect, so force it to allocate user addr */
        __kmalloc_fake = __user_addr_min + vring_size(RINGSIZE, ALIGN);
        err = virtqueue_add_sgs(vq, sgs, 1, 1, &err, GFP_KERNEL);
        if (err)
                errx(1, "virtqueue_add_sgs: %i", err);
        __kmalloc_fake = NULL;

        /* Host retrieves 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_outbuf(vq, guest_sg, RINGSIZE, &err, GFP_KERNEL);
        if (err)
                errx(1, "virtqueue_add_outbuf (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_outbuf(vq, guest_sg, 1, &err, GFP_KERNEL);
                if (err)
                        errx(1, "virtqueue_add_outbuf (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 (__virtio_test_bit(&vdev, 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. */
                __virtio_clear_bit(&vdev, VIRTIO_RING_F_INDIRECT_DESC);
                vq = vring_new_virtqueue(0, RINGSIZE, ALIGN, &vdev, true,
                                         false, __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_outbuf(vq, guest_sg, 4, &err, GFP_KERNEL);
                if (err)
                        errx(1, "virtqueue_add_outbuf (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;
}