Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 2520 insertions, 0 deletions

diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
new file mode 100644
index 000000000..46593d632
--- /dev/null
+++ b/qemu-io-cmds.c
@@ -0,0 +1,2520 @@
+/*
+ * Command line utility to exercise the QEMU I/O path.
+ *
+ * Copyright (C) 2009-2016 Red Hat, Inc.
+ * Copyright (c) 2003-2005 Silicon Graphics, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "qemu-io.h"
+#include "sysemu/block-backend.h"
+#include "block/block.h"
+#include "block/block_int.h" /* for info_f() */
+#include "block/qapi.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+#include "qemu/option.h"
+#include "qemu/timer.h"
+#include "qemu/cutils.h"
+
+#define CMD_NOFILE_OK   0x01
+
+bool qemuio_misalign;
+
+static cmdinfo_t *cmdtab;
+static int ncmds;
+
+static int compare_cmdname(const void *a, const void *b)
+{
+    return strcmp(((const cmdinfo_t *)a)->name,
+                  ((const cmdinfo_t *)b)->name);
+}
+
+void qemuio_add_command(const cmdinfo_t *ci)
+{
+    /* ci->perm assumes a file is open, but the GLOBAL and NOFILE_OK
+     * flags allow it not to be, so that combination is invalid.
+     * Catch it now rather than letting it manifest as a crash if a
+     * particular set of command line options are used.
+     */
+    assert(ci->perm == 0 ||
+           (ci->flags & (CMD_FLAG_GLOBAL | CMD_NOFILE_OK)) == 0);
+    cmdtab = g_renew(cmdinfo_t, cmdtab, ++ncmds);
+    cmdtab[ncmds - 1] = *ci;
+    qsort(cmdtab, ncmds, sizeof(*cmdtab), compare_cmdname);
+}
+
+void qemuio_command_usage(const cmdinfo_t *ci)
+{
+    printf("%s %s -- %s\n", ci->name, ci->args, ci->oneline);
+}
+
+static int init_check_command(BlockBackend *blk, const cmdinfo_t *ct)
+{
+    if (ct->flags & CMD_FLAG_GLOBAL) {
+        return 1;
+    }
+    if (!(ct->flags & CMD_NOFILE_OK) && !blk) {
+        fprintf(stderr, "no file open, try 'help open'\n");
+        return 0;
+    }
+    return 1;
+}
+
+static int command(BlockBackend *blk, const cmdinfo_t *ct, int argc,
+                   char **argv)
+{
+    char *cmd = argv[0];
+
+    if (!init_check_command(blk, ct)) {
+        return -EINVAL;
+    }
+
+    if (argc - 1 < ct->argmin || (ct->argmax != -1 && argc - 1 > ct->argmax)) {
+        if (ct->argmax == -1) {
+            fprintf(stderr,
+                    "bad argument count %d to %s, expected at least %d arguments\n",
+                    argc-1, cmd, ct->argmin);
+        } else if (ct->argmin == ct->argmax) {
+            fprintf(stderr,
+                    "bad argument count %d to %s, expected %d arguments\n",
+                    argc-1, cmd, ct->argmin);
+        } else {
+            fprintf(stderr,
+                    "bad argument count %d to %s, expected between %d and %d arguments\n",
+                    argc-1, cmd, ct->argmin, ct->argmax);
+        }
+        return -EINVAL;
+    }
+
+    /*
+     * Request additional permissions if necessary for this command. The caller
+     * is responsible for restoring the original permissions afterwards if this
+     * is what it wants.
+     *
+     * Coverity thinks that blk may be NULL in the following if condition. It's
+     * not so: in init_check_command() we fail if blk is NULL for command with
+     * both CMD_FLAG_GLOBAL and CMD_NOFILE_OK flags unset. And in
+     * qemuio_add_command() we assert that command with non-zero .perm field
+     * doesn't set this flags. So, the following assertion is to silence
+     * Coverity:
+     */
+    assert(blk || !ct->perm);
+    if (ct->perm && blk_is_available(blk)) {
+        uint64_t orig_perm, orig_shared_perm;
+        blk_get_perm(blk, &orig_perm, &orig_shared_perm);
+
+        if (ct->perm & ~orig_perm) {
+            uint64_t new_perm;
+            Error *local_err = NULL;
+            int ret;
+
+            new_perm = orig_perm | ct->perm;
+
+            ret = blk_set_perm(blk, new_perm, orig_shared_perm, &local_err);
+            if (ret < 0) {
+                error_report_err(local_err);
+                return ret;
+            }
+        }
+    }
+
+    qemu_reset_optind();
+    return ct->cfunc(blk, argc, argv);
+}
+
+static const cmdinfo_t *find_command(const char *cmd)
+{
+    cmdinfo_t *ct;
+
+    for (ct = cmdtab; ct < &cmdtab[ncmds]; ct++) {
+        if (strcmp(ct->name, cmd) == 0 ||
+            (ct->altname && strcmp(ct->altname, cmd) == 0))
+        {
+            return (const cmdinfo_t *)ct;
+        }
+    }
+    return NULL;
+}
+
+/* Invoke fn() for commands with a matching prefix */
+void qemuio_complete_command(const char *input,
+                             void (*fn)(const char *cmd, void *opaque),
+                             void *opaque)
+{
+    cmdinfo_t *ct;
+    size_t input_len = strlen(input);
+
+    for (ct = cmdtab; ct < &cmdtab[ncmds]; ct++) {
+        if (strncmp(input, ct->name, input_len) == 0) {
+            fn(ct->name, opaque);
+        }
+    }
+}
+
+static char **breakline(char *input, int *count)
+{
+    int c = 0;
+    char *p;
+    char **rval = g_new0(char *, 1);
+
+    while (rval && (p = qemu_strsep(&input, " ")) != NULL) {
+        if (!*p) {
+            continue;
+        }
+        c++;
+        rval = g_renew(char *, rval, (c + 1));
+        rval[c - 1] = p;
+        rval[c] = NULL;
+    }
+    *count = c;
+    return rval;
+}
+
+static int64_t cvtnum(const char *s)
+{
+    int err;
+    uint64_t value;
+
+    err = qemu_strtosz(s, NULL, &value);
+    if (err < 0) {
+        return err;
+    }
+    if (value > INT64_MAX) {
+        return -ERANGE;
+    }
+    return value;
+}
+
+static void print_cvtnum_err(int64_t rc, const char *arg)
+{
+    switch (rc) {
+    case -EINVAL:
+        printf("Parsing error: non-numeric argument,"
+               " or extraneous/unrecognized suffix -- %s\n", arg);
+        break;
+    case -ERANGE:
+        printf("Parsing error: argument too large -- %s\n", arg);
+        break;
+    default:
+        printf("Parsing error: %s\n", arg);
+    }
+}
+
+#define EXABYTES(x)     ((long long)(x) << 60)
+#define PETABYTES(x)    ((long long)(x) << 50)
+#define TERABYTES(x)    ((long long)(x) << 40)
+#define GIGABYTES(x)    ((long long)(x) << 30)
+#define MEGABYTES(x)    ((long long)(x) << 20)
+#define KILOBYTES(x)    ((long long)(x) << 10)
+
+#define TO_EXABYTES(x)  ((x) / EXABYTES(1))
+#define TO_PETABYTES(x) ((x) / PETABYTES(1))
+#define TO_TERABYTES(x) ((x) / TERABYTES(1))
+#define TO_GIGABYTES(x) ((x) / GIGABYTES(1))
+#define TO_MEGABYTES(x) ((x) / MEGABYTES(1))
+#define TO_KILOBYTES(x) ((x) / KILOBYTES(1))
+
+static void cvtstr(double value, char *str, size_t size)
+{
+    char *trim;
+    const char *suffix;
+
+    if (value >= EXABYTES(1)) {
+        suffix = " EiB";
+        snprintf(str, size - 4, "%.3f", TO_EXABYTES(value));
+    } else if (value >= PETABYTES(1)) {
+        suffix = " PiB";
+        snprintf(str, size - 4, "%.3f", TO_PETABYTES(value));
+    } else if (value >= TERABYTES(1)) {
+        suffix = " TiB";
+        snprintf(str, size - 4, "%.3f", TO_TERABYTES(value));
+    } else if (value >= GIGABYTES(1)) {
+        suffix = " GiB";
+        snprintf(str, size - 4, "%.3f", TO_GIGABYTES(value));
+    } else if (value >= MEGABYTES(1)) {
+        suffix = " MiB";
+        snprintf(str, size - 4, "%.3f", TO_MEGABYTES(value));
+    } else if (value >= KILOBYTES(1)) {
+        suffix = " KiB";
+        snprintf(str, size - 4, "%.3f", TO_KILOBYTES(value));
+    } else {
+        suffix = " bytes";
+        snprintf(str, size - 6, "%f", value);
+    }
+
+    trim = strstr(str, ".000");
+    if (trim) {
+        strcpy(trim, suffix);
+    } else {
+        strcat(str, suffix);
+    }
+}
+
+
+
+static struct timespec tsub(struct timespec t1, struct timespec t2)
+{
+    t1.tv_nsec -= t2.tv_nsec;
+    if (t1.tv_nsec < 0) {
+        t1.tv_nsec += NANOSECONDS_PER_SECOND;
+        t1.tv_sec--;
+    }
+    t1.tv_sec -= t2.tv_sec;
+    return t1;
+}
+
+static double tdiv(double value, struct timespec tv)
+{
+    double seconds = tv.tv_sec + (tv.tv_nsec / 1e9);
+    return value / seconds;
+}
+
+#define HOURS(sec)      ((sec) / (60 * 60))
+#define MINUTES(sec)    (((sec) % (60 * 60)) / 60)
+#define SECONDS(sec)    ((sec) % 60)
+
+enum {
+    DEFAULT_TIME        = 0x0,
+    TERSE_FIXED_TIME    = 0x1,
+    VERBOSE_FIXED_TIME  = 0x2,
+};
+
+static void timestr(struct timespec *tv, char *ts, size_t size, int format)
+{
+    double frac_sec = tv->tv_nsec / 1e9;
+
+    if (format & TERSE_FIXED_TIME) {
+        if (!HOURS(tv->tv_sec)) {
+            snprintf(ts, size, "%u:%05.2f",
+                     (unsigned int) MINUTES(tv->tv_sec),
+                     SECONDS(tv->tv_sec) + frac_sec);
+            return;
+        }
+        format |= VERBOSE_FIXED_TIME; /* fallback if hours needed */
+    }
+
+    if ((format & VERBOSE_FIXED_TIME) || tv->tv_sec) {
+        snprintf(ts, size, "%u:%02u:%05.2f",
+                (unsigned int) HOURS(tv->tv_sec),
+                (unsigned int) MINUTES(tv->tv_sec),
+                 SECONDS(tv->tv_sec) + frac_sec);
+    } else {
+        snprintf(ts, size, "%05.2f sec", frac_sec);
+    }
+}
+
+/*
+ * Parse the pattern argument to various sub-commands.
+ *
+ * Because the pattern is used as an argument to memset it must evaluate
+ * to an unsigned integer that fits into a single byte.
+ */
+static int parse_pattern(const char *arg)
+{
+    char *endptr = NULL;
+    long pattern;
+
+    pattern = strtol(arg, &endptr, 0);
+    if (pattern < 0 || pattern > UCHAR_MAX || *endptr != '\0') {
+        printf("%s is not a valid pattern byte\n", arg);
+        return -1;
+    }
+
+    return pattern;
+}
+
+/*
+ * Memory allocation helpers.
+ *
+ * Make sure memory is aligned by default, or purposefully misaligned if
+ * that is specified on the command line.
+ */
+
+#define MISALIGN_OFFSET     16
+static void *qemu_io_alloc(BlockBackend *blk, size_t len, int pattern)
+{
+    void *buf;
+
+    if (qemuio_misalign) {
+        len += MISALIGN_OFFSET;
+    }
+    buf = blk_blockalign(blk, len);
+    memset(buf, pattern, len);
+    if (qemuio_misalign) {
+        buf += MISALIGN_OFFSET;
+    }
+    return buf;
+}
+
+static void qemu_io_free(void *p)
+{
+    if (qemuio_misalign) {
+        p -= MISALIGN_OFFSET;
+    }
+    qemu_vfree(p);
+}
+
+/*
+ * qemu_io_alloc_from_file()
+ *
+ * Allocates the buffer and populates it with the content of the given file
+ * up to @len bytes. If the file length is less than @len, then the buffer
+ * is populated with the file content cyclically.
+ *
+ * @blk - the block backend where the buffer content is going to be written to
+ * @len - the buffer length
+ * @file_name - the file to read the content from
+ *
+ * Returns: the buffer pointer on success
+ *          NULL on error
+ */
+static void *qemu_io_alloc_from_file(BlockBackend *blk, size_t len,
+                                     const char *file_name)
+{
+    char *buf, *buf_origin;
+    FILE *f = fopen(file_name, "r");
+    int pattern_len;
+
+    if (!f) {
+        perror(file_name);
+        return NULL;
+    }
+
+    if (qemuio_misalign) {
+        len += MISALIGN_OFFSET;
+    }
+
+    buf_origin = buf = blk_blockalign(blk, len);
+
+    if (qemuio_misalign) {
+        buf_origin += MISALIGN_OFFSET;
+        buf += MISALIGN_OFFSET;
+        len -= MISALIGN_OFFSET;
+    }
+
+    pattern_len = fread(buf_origin, 1, len, f);
+
+    if (ferror(f)) {
+        perror(file_name);
+        goto error;
+    }
+
+    if (pattern_len == 0) {
+        fprintf(stderr, "%s: file is empty\n", file_name);
+        goto error;
+    }
+
+    fclose(f);
+    f = NULL;
+
+    if (len > pattern_len) {
+        len -= pattern_len;
+        buf += pattern_len;
+
+        while (len > 0) {
+            size_t len_to_copy = MIN(pattern_len, len);
+
+            memcpy(buf, buf_origin, len_to_copy);
+
+            len -= len_to_copy;
+            buf += len_to_copy;
+        }
+    }
+
+    return buf_origin;
+
+error:
+    qemu_io_free(buf_origin);
+    if (f) {
+        fclose(f);
+    }
+    return NULL;
+}
+
+static void dump_buffer(const void *buffer, int64_t offset, int64_t len)
+{
+    uint64_t i;
+    int j;
+    const uint8_t *p;
+
+    for (i = 0, p = buffer; i < len; i += 16) {
+        const uint8_t *s = p;
+
+        printf("%08" PRIx64 ":  ", offset + i);
+        for (j = 0; j < 16 && i + j < len; j++, p++) {
+            printf("%02x ", *p);
+        }
+        printf(" ");
+        for (j = 0; j < 16 && i + j < len; j++, s++) {
+            if (isalnum(*s)) {
+                printf("%c", *s);
+            } else {
+                printf(".");
+            }
+        }
+        printf("\n");
+    }
+}
+
+static void print_report(const char *op, struct timespec *t, int64_t offset,
+                         int64_t count, int64_t total, int cnt, bool Cflag)
+{
+    char s1[64], s2[64], ts[64];
+
+    timestr(t, ts, sizeof(ts), Cflag ? VERBOSE_FIXED_TIME : 0);
+    if (!Cflag) {
+        cvtstr((double)total, s1, sizeof(s1));
+        cvtstr(tdiv((double)total, *t), s2, sizeof(s2));
+        printf("%s %"PRId64"/%"PRId64" bytes at offset %" PRId64 "\n",
+               op, total, count, offset);
+        printf("%s, %d ops; %s (%s/sec and %.4f ops/sec)\n",
+               s1, cnt, ts, s2, tdiv((double)cnt, *t));
+    } else {/* bytes,ops,time,bytes/sec,ops/sec */
+        printf("%"PRId64",%d,%s,%.3f,%.3f\n",
+            total, cnt, ts,
+            tdiv((double)total, *t),
+            tdiv((double)cnt, *t));
+    }
+}
+
+/*
+ * Parse multiple length statements for vectored I/O, and construct an I/O
+ * vector matching it.
+ */
+static void *
+create_iovec(BlockBackend *blk, QEMUIOVector *qiov, char **argv, int nr_iov,
+             int pattern)
+{
+    size_t *sizes = g_new0(size_t, nr_iov);
+    size_t count = 0;
+    void *buf = NULL;
+    void *p;
+    int i;
+
+    for (i = 0; i < nr_iov; i++) {
+        char *arg = argv[i];
+        int64_t len;
+
+        len = cvtnum(arg);
+        if (len < 0) {
+            print_cvtnum_err(len, arg);
+            goto fail;
+        }
+
+        if (len > BDRV_REQUEST_MAX_BYTES) {
+            printf("Argument '%s' exceeds maximum size %" PRIu64 "\n", arg,
+                   (uint64_t)BDRV_REQUEST_MAX_BYTES);
+            goto fail;
+        }
+
+        if (count > BDRV_REQUEST_MAX_BYTES - len) {
+            printf("The total number of bytes exceed the maximum size %" PRIu64
+                   "\n", (uint64_t)BDRV_REQUEST_MAX_BYTES);
+            goto fail;
+        }
+
+        sizes[i] = len;
+        count += len;
+    }
+
+    qemu_iovec_init(qiov, nr_iov);
+
+    buf = p = qemu_io_alloc(blk, count, pattern);
+
+    for (i = 0; i < nr_iov; i++) {
+        qemu_iovec_add(qiov, p, sizes[i]);
+        p += sizes[i];
+    }
+
+fail:
+    g_free(sizes);
+    return buf;
+}
+
+static int do_pread(BlockBackend *blk, char *buf, int64_t offset,
+                    int64_t bytes, int64_t *total)
+{
+    if (bytes > INT_MAX) {
+        return -ERANGE;
+    }
+
+    *total = blk_pread(blk, offset, (uint8_t *)buf, bytes);
+    if (*total < 0) {
+        return *total;
+    }
+    return 1;
+}
+
+static int do_pwrite(BlockBackend *blk, char *buf, int64_t offset,
+                     int64_t bytes, int flags, int64_t *total)
+{
+    if (bytes > INT_MAX) {
+        return -ERANGE;
+    }
+
+    *total = blk_pwrite(blk, offset, (uint8_t *)buf, bytes, flags);
+    if (*total < 0) {
+        return *total;
+    }
+    return 1;
+}
+
+typedef struct {
+    BlockBackend *blk;
+    int64_t offset;
+    int64_t bytes;
+    int64_t *total;
+    int flags;
+    int ret;
+    bool done;
+} CoWriteZeroes;
+
+static void coroutine_fn co_pwrite_zeroes_entry(void *opaque)
+{
+    CoWriteZeroes *data = opaque;
+
+    data->ret = blk_co_pwrite_zeroes(data->blk, data->offset, data->bytes,
+                                     data->flags);
+    data->done = true;
+    if (data->ret < 0) {
+        *data->total = data->ret;
+        return;
+    }
+
+    *data->total = data->bytes;
+}
+
+static int do_co_pwrite_zeroes(BlockBackend *blk, int64_t offset,
+                               int64_t bytes, int flags, int64_t *total)
+{
+    Coroutine *co;
+    CoWriteZeroes data = {
+        .blk    = blk,
+        .offset = offset,
+        .bytes  = bytes,
+        .total  = total,
+        .flags  = flags,
+        .done   = false,
+    };
+
+    if (bytes > INT_MAX) {
+        return -ERANGE;
+    }
+
+    co = qemu_coroutine_create(co_pwrite_zeroes_entry, &data);
+    bdrv_coroutine_enter(blk_bs(blk), co);
+    while (!data.done) {
+        aio_poll(blk_get_aio_context(blk), true);
+    }
+    if (data.ret < 0) {
+        return data.ret;
+    } else {
+        return 1;
+    }
+}
+
+static int do_write_compressed(BlockBackend *blk, char *buf, int64_t offset,
+                               int64_t bytes, int64_t *total)
+{
+    int ret;
+
+    if (bytes > BDRV_REQUEST_MAX_BYTES) {
+        return -ERANGE;
+    }
+
+    ret = blk_pwrite_compressed(blk, offset, buf, bytes);
+    if (ret < 0) {
+        return ret;
+    }
+    *total = bytes;
+    return 1;
+}
+
+static int do_load_vmstate(BlockBackend *blk, char *buf, int64_t offset,
+                           int64_t count, int64_t *total)
+{
+    if (count > INT_MAX) {
+        return -ERANGE;
+    }
+
+    *total = blk_load_vmstate(blk, (uint8_t *)buf, offset, count);
+    if (*total < 0) {
+        return *total;
+    }
+    return 1;
+}
+
+static int do_save_vmstate(BlockBackend *blk, char *buf, int64_t offset,
+                           int64_t count, int64_t *total)
+{
+    if (count > INT_MAX) {
+        return -ERANGE;
+    }
+
+    *total = blk_save_vmstate(blk, (uint8_t *)buf, offset, count);
+    if (*total < 0) {
+        return *total;
+    }
+    return 1;
+}
+
+#define NOT_DONE 0x7fffffff
+static void aio_rw_done(void *opaque, int ret)
+{
+    *(int *)opaque = ret;
+}
+
+static int do_aio_readv(BlockBackend *blk, QEMUIOVector *qiov,
+                        int64_t offset, int *total)
+{
+    int async_ret = NOT_DONE;
+
+    blk_aio_preadv(blk, offset, qiov, 0, aio_rw_done, &async_ret);
+    while (async_ret == NOT_DONE) {
+        main_loop_wait(false);
+    }
+
+    *total = qiov->size;
+    return async_ret < 0 ? async_ret : 1;
+}
+
+static int do_aio_writev(BlockBackend *blk, QEMUIOVector *qiov,
+                         int64_t offset, int flags, int *total)
+{
+    int async_ret = NOT_DONE;
+
+    blk_aio_pwritev(blk, offset, qiov, flags, aio_rw_done, &async_ret);
+    while (async_ret == NOT_DONE) {
+        main_loop_wait(false);
+    }
+
+    *total = qiov->size;
+    return async_ret < 0 ? async_ret : 1;
+}
+
+static void read_help(void)
+{
+    printf(
+"\n"
+" reads a range of bytes from the given offset\n"
+"\n"
+" Example:\n"
+" 'read -v 512 1k' - dumps 1 kilobyte read from 512 bytes into the file\n"
+"\n"
+" Reads a segment of the currently open file, optionally dumping it to the\n"
+" standard output stream (with -v option) for subsequent inspection.\n"
+" -b, -- read from the VM state rather than the virtual disk\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -l, -- length for pattern verification (only with -P)\n"
+" -p, -- ignored for backwards compatibility\n"
+" -P, -- use a pattern to verify read data\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+" -s, -- start offset for pattern verification (only with -P)\n"
+" -v, -- dump buffer to standard output\n"
+"\n");
+}
+
+static int read_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t read_cmd = {
+    .name       = "read",
+    .altname    = "r",
+    .cfunc      = read_f,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-abCqv] [-P pattern [-s off] [-l len]] off len",
+    .oneline    = "reads a number of bytes at a specified offset",
+    .help       = read_help,
+};
+
+static int read_f(BlockBackend *blk, int argc, char **argv)
+{
+    struct timespec t1, t2;
+    bool Cflag = false, qflag = false, vflag = false;
+    bool Pflag = false, sflag = false, lflag = false, bflag = false;
+    int c, cnt, ret;
+    char *buf;
+    int64_t offset;
+    int64_t count;
+    /* Some compilers get confused and warn if this is not initialized.  */
+    int64_t total = 0;
+    int pattern = 0;
+    int64_t pattern_offset = 0, pattern_count = 0;
+
+    while ((c = getopt(argc, argv, "bCl:pP:qs:v")) != -1) {
+        switch (c) {
+        case 'b':
+            bflag = true;
+            break;
+        case 'C':
+            Cflag = true;
+            break;
+        case 'l':
+            lflag = true;
+            pattern_count = cvtnum(optarg);
+            if (pattern_count < 0) {
+                print_cvtnum_err(pattern_count, optarg);
+                return pattern_count;
+            }
+            break;
+        case 'p':
+            /* Ignored for backwards compatibility */
+            break;
+        case 'P':
+            Pflag = true;
+            pattern = parse_pattern(optarg);
+            if (pattern < 0) {
+                return -EINVAL;
+            }
+            break;
+        case 'q':
+            qflag = true;
+            break;
+        case 's':
+            sflag = true;
+            pattern_offset = cvtnum(optarg);
+            if (pattern_offset < 0) {
+                print_cvtnum_err(pattern_offset, optarg);
+                return pattern_offset;
+            }
+            break;
+        case 'v':
+            vflag = true;
+            break;
+        default:
+            qemuio_command_usage(&read_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind != argc - 2) {
+        qemuio_command_usage(&read_cmd);
+        return -EINVAL;
+    }
+
+    offset = cvtnum(argv[optind]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[optind]);
+        return offset;
+    }
+
+    optind++;
+    count = cvtnum(argv[optind]);
+    if (count < 0) {
+        print_cvtnum_err(count, argv[optind]);
+        return count;
+    } else if (count > BDRV_REQUEST_MAX_BYTES) {
+        printf("length cannot exceed %" PRIu64 ", given %s\n",
+               (uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]);
+        return -EINVAL;
+    }
+
+    if (!Pflag && (lflag || sflag)) {
+        qemuio_command_usage(&read_cmd);
+        return -EINVAL;
+    }
+
+    if (!lflag) {
+        pattern_count = count - pattern_offset;
+    }
+
+    if ((pattern_count < 0) || (pattern_count + pattern_offset > count))  {
+        printf("pattern verification range exceeds end of read data\n");
+        return -EINVAL;
+    }
+
+    if (bflag) {
+        if (!QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)) {
+            printf("%" PRId64 " is not a sector-aligned value for 'offset'\n",
+                   offset);
+            return -EINVAL;
+        }
+        if (!QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE)) {
+            printf("%"PRId64" is not a sector-aligned value for 'count'\n",
+                   count);
+            return -EINVAL;
+        }
+    }
+
+    buf = qemu_io_alloc(blk, count, 0xab);
+
+    clock_gettime(CLOCK_MONOTONIC, &t1);
+    if (bflag) {
+        ret = do_load_vmstate(blk, buf, offset, count, &total);
+    } else {
+        ret = do_pread(blk, buf, offset, count, &total);
+    }
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+    if (ret < 0) {
+        printf("read failed: %s\n", strerror(-ret));
+        goto out;
+    }
+    cnt = ret;
+
+    ret = 0;
+
+    if (Pflag) {
+        void *cmp_buf = g_malloc(pattern_count);
+        memset(cmp_buf, pattern, pattern_count);
+        if (memcmp(buf + pattern_offset, cmp_buf, pattern_count)) {
+            printf("Pattern verification failed at offset %"
+                   PRId64 ", %"PRId64" bytes\n",
+                   offset + pattern_offset, pattern_count);
+            ret = -EINVAL;
+        }
+        g_free(cmp_buf);
+    }
+
+    if (qflag) {
+        goto out;
+    }
+
+    if (vflag) {
+        dump_buffer(buf, offset, count);
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    t2 = tsub(t2, t1);
+    print_report("read", &t2, offset, count, total, cnt, Cflag);
+
+out:
+    qemu_io_free(buf);
+    return ret;
+}
+
+static void readv_help(void)
+{
+    printf(
+"\n"
+" reads a range of bytes from the given offset into multiple buffers\n"
+"\n"
+" Example:\n"
+" 'readv -v 512 1k 1k ' - dumps 2 kilobytes read from 512 bytes into the file\n"
+"\n"
+" Reads a segment of the currently open file, optionally dumping it to the\n"
+" standard output stream (with -v option) for subsequent inspection.\n"
+" Uses multiple iovec buffers if more than one byte range is specified.\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -P, -- use a pattern to verify read data\n"
+" -v, -- dump buffer to standard output\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+"\n");
+}
+
+static int readv_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t readv_cmd = {
+    .name       = "readv",
+    .cfunc      = readv_f,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-Cqv] [-P pattern] off len [len..]",
+    .oneline    = "reads a number of bytes at a specified offset",
+    .help       = readv_help,
+};
+
+static int readv_f(BlockBackend *blk, int argc, char **argv)
+{
+    struct timespec t1, t2;
+    bool Cflag = false, qflag = false, vflag = false;
+    int c, cnt, ret;
+    char *buf;
+    int64_t offset;
+    /* Some compilers get confused and warn if this is not initialized.  */
+    int total = 0;
+    int nr_iov;
+    QEMUIOVector qiov;
+    int pattern = 0;
+    bool Pflag = false;
+
+    while ((c = getopt(argc, argv, "CP:qv")) != -1) {
+        switch (c) {
+        case 'C':
+            Cflag = true;
+            break;
+        case 'P':
+            Pflag = true;
+            pattern = parse_pattern(optarg);
+            if (pattern < 0) {
+                return -EINVAL;
+            }
+            break;
+        case 'q':
+            qflag = true;
+            break;
+        case 'v':
+            vflag = true;
+            break;
+        default:
+            qemuio_command_usage(&readv_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind > argc - 2) {
+        qemuio_command_usage(&readv_cmd);
+        return -EINVAL;
+    }
+
+
+    offset = cvtnum(argv[optind]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[optind]);
+        return offset;
+    }
+    optind++;
+
+    nr_iov = argc - optind;
+    buf = create_iovec(blk, &qiov, &argv[optind], nr_iov, 0xab);
+    if (buf == NULL) {
+        return -EINVAL;
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &t1);
+    ret = do_aio_readv(blk, &qiov, offset, &total);
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+    if (ret < 0) {
+        printf("readv failed: %s\n", strerror(-ret));
+        goto out;
+    }
+    cnt = ret;
+
+    ret = 0;
+
+    if (Pflag) {
+        void *cmp_buf = g_malloc(qiov.size);
+        memset(cmp_buf, pattern, qiov.size);
+        if (memcmp(buf, cmp_buf, qiov.size)) {
+            printf("Pattern verification failed at offset %"
+                   PRId64 ", %zu bytes\n", offset, qiov.size);
+            ret = -EINVAL;
+        }
+        g_free(cmp_buf);
+    }
+
+    if (qflag) {
+        goto out;
+    }
+
+    if (vflag) {
+        dump_buffer(buf, offset, qiov.size);
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    t2 = tsub(t2, t1);
+    print_report("read", &t2, offset, qiov.size, total, cnt, Cflag);
+
+out:
+    qemu_iovec_destroy(&qiov);
+    qemu_io_free(buf);
+    return ret;
+}
+
+static void write_help(void)
+{
+    printf(
+"\n"
+" writes a range of bytes from the given offset\n"
+"\n"
+" Example:\n"
+" 'write 512 1k' - writes 1 kilobyte at 512 bytes into the open file\n"
+"\n"
+" Writes into a segment of the currently open file, using a buffer\n"
+" filled with a set pattern (0xcdcdcdcd).\n"
+" -b, -- write to the VM state rather than the virtual disk\n"
+" -c, -- write compressed data with blk_write_compressed\n"
+" -f, -- use Force Unit Access semantics\n"
+" -n, -- with -z, don't allow slow fallback\n"
+" -p, -- ignored for backwards compatibility\n"
+" -P, -- use different pattern to fill file\n"
+" -s, -- use a pattern file to fill the write buffer\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+" -u, -- with -z, allow unmapping\n"
+" -z, -- write zeroes using blk_co_pwrite_zeroes\n"
+"\n");
+}
+
+static int write_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t write_cmd = {
+    .name       = "write",
+    .altname    = "w",
+    .cfunc      = write_f,
+    .perm       = BLK_PERM_WRITE,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-bcCfnquz] [-P pattern | -s source_file] off len",
+    .oneline    = "writes a number of bytes at a specified offset",
+    .help       = write_help,
+};
+
+static int write_f(BlockBackend *blk, int argc, char **argv)
+{
+    struct timespec t1, t2;
+    bool Cflag = false, qflag = false, bflag = false;
+    bool Pflag = false, zflag = false, cflag = false, sflag = false;
+    int flags = 0;
+    int c, cnt, ret;
+    char *buf = NULL;
+    int64_t offset;
+    int64_t count;
+    /* Some compilers get confused and warn if this is not initialized.  */
+    int64_t total = 0;
+    int pattern = 0xcd;
+    const char *file_name = NULL;
+
+    while ((c = getopt(argc, argv, "bcCfnpP:qs:uz")) != -1) {
+        switch (c) {
+        case 'b':
+            bflag = true;
+            break;
+        case 'c':
+            cflag = true;
+            break;
+        case 'C':
+            Cflag = true;
+            break;
+        case 'f':
+            flags |= BDRV_REQ_FUA;
+            break;
+        case 'n':
+            flags |= BDRV_REQ_NO_FALLBACK;
+            break;
+        case 'p':
+            /* Ignored for backwards compatibility */
+            break;
+        case 'P':
+            Pflag = true;
+            pattern = parse_pattern(optarg);
+            if (pattern < 0) {
+                return -EINVAL;
+            }
+            break;
+        case 'q':
+            qflag = true;
+            break;
+        case 's':
+            sflag = true;
+            file_name = optarg;
+            break;
+        case 'u':
+            flags |= BDRV_REQ_MAY_UNMAP;
+            break;
+        case 'z':
+            zflag = true;
+            break;
+        default:
+            qemuio_command_usage(&write_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind != argc - 2) {
+        qemuio_command_usage(&write_cmd);
+        return -EINVAL;
+    }
+
+    if (bflag && zflag) {
+        printf("-b and -z cannot be specified at the same time\n");
+        return -EINVAL;
+    }
+
+    if ((flags & BDRV_REQ_FUA) && (bflag || cflag)) {
+        printf("-f and -b or -c cannot be specified at the same time\n");
+        return -EINVAL;
+    }
+
+    if ((flags & BDRV_REQ_NO_FALLBACK) && !zflag) {
+        printf("-n requires -z to be specified\n");
+        return -EINVAL;
+    }
+
+    if ((flags & BDRV_REQ_MAY_UNMAP) && !zflag) {
+        printf("-u requires -z to be specified\n");
+        return -EINVAL;
+    }
+
+    if (zflag + Pflag + sflag > 1) {
+        printf("Only one of -z, -P, and -s "
+               "can be specified at the same time\n");
+        return -EINVAL;
+    }
+
+    offset = cvtnum(argv[optind]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[optind]);
+        return offset;
+    }
+
+    optind++;
+    count = cvtnum(argv[optind]);
+    if (count < 0) {
+        print_cvtnum_err(count, argv[optind]);
+        return count;
+    } else if (count > BDRV_REQUEST_MAX_BYTES) {
+        printf("length cannot exceed %" PRIu64 ", given %s\n",
+               (uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]);
+        return -EINVAL;
+    }
+
+    if (bflag || cflag) {
+        if (!QEMU_IS_ALIGNED(offset, BDRV_SECTOR_SIZE)) {
+            printf("%" PRId64 " is not a sector-aligned value for 'offset'\n",
+                   offset);
+            return -EINVAL;
+        }
+
+        if (!QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE)) {
+            printf("%"PRId64" is not a sector-aligned value for 'count'\n",
+                   count);
+            return -EINVAL;
+        }
+    }
+
+    if (!zflag) {
+        if (sflag) {
+            buf = qemu_io_alloc_from_file(blk, count, file_name);
+            if (!buf) {
+                return -EINVAL;
+            }
+        } else {
+            buf = qemu_io_alloc(blk, count, pattern);
+        }
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &t1);
+    if (bflag) {
+        ret = do_save_vmstate(blk, buf, offset, count, &total);
+    } else if (zflag) {
+        ret = do_co_pwrite_zeroes(blk, offset, count, flags, &total);
+    } else if (cflag) {
+        ret = do_write_compressed(blk, buf, offset, count, &total);
+    } else {
+        ret = do_pwrite(blk, buf, offset, count, flags, &total);
+    }
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+    if (ret < 0) {
+        printf("write failed: %s\n", strerror(-ret));
+        goto out;
+    }
+    cnt = ret;
+
+    ret = 0;
+
+    if (qflag) {
+        goto out;
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    t2 = tsub(t2, t1);
+    print_report("wrote", &t2, offset, count, total, cnt, Cflag);
+
+out:
+    if (!zflag) {
+        qemu_io_free(buf);
+    }
+    return ret;
+}
+
+static void
+writev_help(void)
+{
+    printf(
+"\n"
+" writes a range of bytes from the given offset source from multiple buffers\n"
+"\n"
+" Example:\n"
+" 'writev 512 1k 1k' - writes 2 kilobytes at 512 bytes into the open file\n"
+"\n"
+" Writes into a segment of the currently open file, using a buffer\n"
+" filled with a set pattern (0xcdcdcdcd).\n"
+" -P, -- use different pattern to fill file\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -f, -- use Force Unit Access semantics\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+"\n");
+}
+
+static int writev_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t writev_cmd = {
+    .name       = "writev",
+    .cfunc      = writev_f,
+    .perm       = BLK_PERM_WRITE,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-Cfq] [-P pattern] off len [len..]",
+    .oneline    = "writes a number of bytes at a specified offset",
+    .help       = writev_help,
+};
+
+static int writev_f(BlockBackend *blk, int argc, char **argv)
+{
+    struct timespec t1, t2;
+    bool Cflag = false, qflag = false;
+    int flags = 0;
+    int c, cnt, ret;
+    char *buf;
+    int64_t offset;
+    /* Some compilers get confused and warn if this is not initialized.  */
+    int total = 0;
+    int nr_iov;
+    int pattern = 0xcd;
+    QEMUIOVector qiov;
+
+    while ((c = getopt(argc, argv, "CfqP:")) != -1) {
+        switch (c) {
+        case 'C':
+            Cflag = true;
+            break;
+        case 'f':
+            flags |= BDRV_REQ_FUA;
+            break;
+        case 'q':
+            qflag = true;
+            break;
+        case 'P':
+            pattern = parse_pattern(optarg);
+            if (pattern < 0) {
+                return -EINVAL;
+            }
+            break;
+        default:
+            qemuio_command_usage(&writev_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind > argc - 2) {
+        qemuio_command_usage(&writev_cmd);
+        return -EINVAL;
+    }
+
+    offset = cvtnum(argv[optind]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[optind]);
+        return offset;
+    }
+    optind++;
+
+    nr_iov = argc - optind;
+    buf = create_iovec(blk, &qiov, &argv[optind], nr_iov, pattern);
+    if (buf == NULL) {
+        return -EINVAL;
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &t1);
+    ret = do_aio_writev(blk, &qiov, offset, flags, &total);
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+    if (ret < 0) {
+        printf("writev failed: %s\n", strerror(-ret));
+        goto out;
+    }
+    cnt = ret;
+
+    ret = 0;
+
+    if (qflag) {
+        goto out;
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    t2 = tsub(t2, t1);
+    print_report("wrote", &t2, offset, qiov.size, total, cnt, Cflag);
+out:
+    qemu_iovec_destroy(&qiov);
+    qemu_io_free(buf);
+    return ret;
+}
+
+struct aio_ctx {
+    BlockBackend *blk;
+    QEMUIOVector qiov;
+    int64_t offset;
+    char *buf;
+    bool qflag;
+    bool vflag;
+    bool Cflag;
+    bool Pflag;
+    bool zflag;
+    BlockAcctCookie acct;
+    int pattern;
+    struct timespec t1;
+};
+
+static void aio_write_done(void *opaque, int ret)
+{
+    struct aio_ctx *ctx = opaque;
+    struct timespec t2;
+
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+
+    if (ret < 0) {
+        printf("aio_write failed: %s\n", strerror(-ret));
+        block_acct_failed(blk_get_stats(ctx->blk), &ctx->acct);
+        goto out;
+    }
+
+    block_acct_done(blk_get_stats(ctx->blk), &ctx->acct);
+
+    if (ctx->qflag) {
+        goto out;
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    t2 = tsub(t2, ctx->t1);
+    print_report("wrote", &t2, ctx->offset, ctx->qiov.size,
+                 ctx->qiov.size, 1, ctx->Cflag);
+out:
+    if (!ctx->zflag) {
+        qemu_io_free(ctx->buf);
+        qemu_iovec_destroy(&ctx->qiov);
+    }
+    g_free(ctx);
+}
+
+static void aio_read_done(void *opaque, int ret)
+{
+    struct aio_ctx *ctx = opaque;
+    struct timespec t2;
+
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+    if (ret < 0) {
+        printf("readv failed: %s\n", strerror(-ret));
+        block_acct_failed(blk_get_stats(ctx->blk), &ctx->acct);
+        goto out;
+    }
+
+    if (ctx->Pflag) {
+        void *cmp_buf = g_malloc(ctx->qiov.size);
+
+        memset(cmp_buf, ctx->pattern, ctx->qiov.size);
+        if (memcmp(ctx->buf, cmp_buf, ctx->qiov.size)) {
+            printf("Pattern verification failed at offset %"
+                   PRId64 ", %zu bytes\n", ctx->offset, ctx->qiov.size);
+        }
+        g_free(cmp_buf);
+    }
+
+    block_acct_done(blk_get_stats(ctx->blk), &ctx->acct);
+
+    if (ctx->qflag) {
+        goto out;
+    }
+
+    if (ctx->vflag) {
+        dump_buffer(ctx->buf, ctx->offset, ctx->qiov.size);
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    t2 = tsub(t2, ctx->t1);
+    print_report("read", &t2, ctx->offset, ctx->qiov.size,
+                 ctx->qiov.size, 1, ctx->Cflag);
+out:
+    qemu_io_free(ctx->buf);
+    qemu_iovec_destroy(&ctx->qiov);
+    g_free(ctx);
+}
+
+static void aio_read_help(void)
+{
+    printf(
+"\n"
+" asynchronously reads a range of bytes from the given offset\n"
+"\n"
+" Example:\n"
+" 'aio_read -v 512 1k 1k ' - dumps 2 kilobytes read from 512 bytes into the file\n"
+"\n"
+" Reads a segment of the currently open file, optionally dumping it to the\n"
+" standard output stream (with -v option) for subsequent inspection.\n"
+" The read is performed asynchronously and the aio_flush command must be\n"
+" used to ensure all outstanding aio requests have been completed.\n"
+" Note that due to its asynchronous nature, this command will be\n"
+" considered successful once the request is submitted, independently\n"
+" of potential I/O errors or pattern mismatches.\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -P, -- use a pattern to verify read data\n"
+" -i, -- treat request as invalid, for exercising stats\n"
+" -v, -- dump buffer to standard output\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+"\n");
+}
+
+static int aio_read_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t aio_read_cmd = {
+    .name       = "aio_read",
+    .cfunc      = aio_read_f,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-Ciqv] [-P pattern] off len [len..]",
+    .oneline    = "asynchronously reads a number of bytes",
+    .help       = aio_read_help,
+};
+
+static int aio_read_f(BlockBackend *blk, int argc, char **argv)
+{
+    int nr_iov, c;
+    struct aio_ctx *ctx = g_new0(struct aio_ctx, 1);
+
+    ctx->blk = blk;
+    while ((c = getopt(argc, argv, "CP:iqv")) != -1) {
+        switch (c) {
+        case 'C':
+            ctx->Cflag = true;
+            break;
+        case 'P':
+            ctx->Pflag = true;
+            ctx->pattern = parse_pattern(optarg);
+            if (ctx->pattern < 0) {
+                g_free(ctx);
+                return -EINVAL;
+            }
+            break;
+        case 'i':
+            printf("injecting invalid read request\n");
+            block_acct_invalid(blk_get_stats(blk), BLOCK_ACCT_READ);
+            g_free(ctx);
+            return 0;
+        case 'q':
+            ctx->qflag = true;
+            break;
+        case 'v':
+            ctx->vflag = true;
+            break;
+        default:
+            g_free(ctx);
+            qemuio_command_usage(&aio_read_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind > argc - 2) {
+        g_free(ctx);
+        qemuio_command_usage(&aio_read_cmd);
+        return -EINVAL;
+    }
+
+    ctx->offset = cvtnum(argv[optind]);
+    if (ctx->offset < 0) {
+        int ret = ctx->offset;
+        print_cvtnum_err(ret, argv[optind]);
+        g_free(ctx);
+        return ret;
+    }
+    optind++;
+
+    nr_iov = argc - optind;
+    ctx->buf = create_iovec(blk, &ctx->qiov, &argv[optind], nr_iov, 0xab);
+    if (ctx->buf == NULL) {
+        block_acct_invalid(blk_get_stats(blk), BLOCK_ACCT_READ);
+        g_free(ctx);
+        return -EINVAL;
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &ctx->t1);
+    block_acct_start(blk_get_stats(blk), &ctx->acct, ctx->qiov.size,
+                     BLOCK_ACCT_READ);
+    blk_aio_preadv(blk, ctx->offset, &ctx->qiov, 0, aio_read_done, ctx);
+    return 0;
+}
+
+static void aio_write_help(void)
+{
+    printf(
+"\n"
+" asynchronously writes a range of bytes from the given offset source\n"
+" from multiple buffers\n"
+"\n"
+" Example:\n"
+" 'aio_write 512 1k 1k' - writes 2 kilobytes at 512 bytes into the open file\n"
+"\n"
+" Writes into a segment of the currently open file, using a buffer\n"
+" filled with a set pattern (0xcdcdcdcd).\n"
+" The write is performed asynchronously and the aio_flush command must be\n"
+" used to ensure all outstanding aio requests have been completed.\n"
+" Note that due to its asynchronous nature, this command will be\n"
+" considered successful once the request is submitted, independently\n"
+" of potential I/O errors or pattern mismatches.\n"
+" -P, -- use different pattern to fill file\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -f, -- use Force Unit Access semantics\n"
+" -i, -- treat request as invalid, for exercising stats\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+" -u, -- with -z, allow unmapping\n"
+" -z, -- write zeroes using blk_aio_pwrite_zeroes\n"
+"\n");
+}
+
+static int aio_write_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t aio_write_cmd = {
+    .name       = "aio_write",
+    .cfunc      = aio_write_f,
+    .perm       = BLK_PERM_WRITE,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-Cfiquz] [-P pattern] off len [len..]",
+    .oneline    = "asynchronously writes a number of bytes",
+    .help       = aio_write_help,
+};
+
+static int aio_write_f(BlockBackend *blk, int argc, char **argv)
+{
+    int nr_iov, c;
+    int pattern = 0xcd;
+    struct aio_ctx *ctx = g_new0(struct aio_ctx, 1);
+    int flags = 0;
+
+    ctx->blk = blk;
+    while ((c = getopt(argc, argv, "CfiqP:uz")) != -1) {
+        switch (c) {
+        case 'C':
+            ctx->Cflag = true;
+            break;
+        case 'f':
+            flags |= BDRV_REQ_FUA;
+            break;
+        case 'q':
+            ctx->qflag = true;
+            break;
+        case 'u':
+            flags |= BDRV_REQ_MAY_UNMAP;
+            break;
+        case 'P':
+            pattern = parse_pattern(optarg);
+            if (pattern < 0) {
+                g_free(ctx);
+                return -EINVAL;
+            }
+            break;
+        case 'i':
+            printf("injecting invalid write request\n");
+            block_acct_invalid(blk_get_stats(blk), BLOCK_ACCT_WRITE);
+            g_free(ctx);
+            return 0;
+        case 'z':
+            ctx->zflag = true;
+            break;
+        default:
+            g_free(ctx);
+            qemuio_command_usage(&aio_write_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind > argc - 2) {
+        g_free(ctx);
+        qemuio_command_usage(&aio_write_cmd);
+        return -EINVAL;
+    }
+
+    if (ctx->zflag && optind != argc - 2) {
+        printf("-z supports only a single length parameter\n");
+        g_free(ctx);
+        return -EINVAL;
+    }
+
+    if ((flags & BDRV_REQ_MAY_UNMAP) && !ctx->zflag) {
+        printf("-u requires -z to be specified\n");
+        g_free(ctx);
+        return -EINVAL;
+    }
+
+    if (ctx->zflag && ctx->Pflag) {
+        printf("-z and -P cannot be specified at the same time\n");
+        g_free(ctx);
+        return -EINVAL;
+    }
+
+    ctx->offset = cvtnum(argv[optind]);
+    if (ctx->offset < 0) {
+        int ret = ctx->offset;
+        print_cvtnum_err(ret, argv[optind]);
+        g_free(ctx);
+        return ret;
+    }
+    optind++;
+
+    if (ctx->zflag) {
+        int64_t count = cvtnum(argv[optind]);
+        if (count < 0) {
+            print_cvtnum_err(count, argv[optind]);
+            g_free(ctx);
+            return count;
+        }
+
+        ctx->qiov.size = count;
+        blk_aio_pwrite_zeroes(blk, ctx->offset, count, flags, aio_write_done,
+                              ctx);
+    } else {
+        nr_iov = argc - optind;
+        ctx->buf = create_iovec(blk, &ctx->qiov, &argv[optind], nr_iov,
+                                pattern);
+        if (ctx->buf == NULL) {
+            block_acct_invalid(blk_get_stats(blk), BLOCK_ACCT_WRITE);
+            g_free(ctx);
+            return -EINVAL;
+        }
+
+        clock_gettime(CLOCK_MONOTONIC, &ctx->t1);
+        block_acct_start(blk_get_stats(blk), &ctx->acct, ctx->qiov.size,
+                         BLOCK_ACCT_WRITE);
+
+        blk_aio_pwritev(blk, ctx->offset, &ctx->qiov, flags, aio_write_done,
+                        ctx);
+    }
+
+    return 0;
+}
+
+static int aio_flush_f(BlockBackend *blk, int argc, char **argv)
+{
+    BlockAcctCookie cookie;
+    block_acct_start(blk_get_stats(blk), &cookie, 0, BLOCK_ACCT_FLUSH);
+    blk_drain_all();
+    block_acct_done(blk_get_stats(blk), &cookie);
+    return 0;
+}
+
+static const cmdinfo_t aio_flush_cmd = {
+    .name       = "aio_flush",
+    .cfunc      = aio_flush_f,
+    .oneline    = "completes all outstanding aio requests"
+};
+
+static int flush_f(BlockBackend *blk, int argc, char **argv)
+{
+    return blk_flush(blk);
+}
+
+static const cmdinfo_t flush_cmd = {
+    .name       = "flush",
+    .altname    = "f",
+    .cfunc      = flush_f,
+    .oneline    = "flush all in-core file state to disk",
+};
+
+static int truncate_f(BlockBackend *blk, int argc, char **argv);
+static const cmdinfo_t truncate_cmd = {
+    .name       = "truncate",
+    .altname    = "t",
+    .cfunc      = truncate_f,
+    .perm       = BLK_PERM_WRITE | BLK_PERM_RESIZE,
+    .argmin     = 1,
+    .argmax     = 3,
+    .args       = "[-m prealloc_mode] off",
+    .oneline    = "truncates the current file at the given offset",
+};
+
+static int truncate_f(BlockBackend *blk, int argc, char **argv)
+{
+    Error *local_err = NULL;
+    int64_t offset;
+    int c, ret;
+    PreallocMode prealloc = PREALLOC_MODE_OFF;
+
+    while ((c = getopt(argc, argv, "m:")) != -1) {
+        switch (c) {
+        case 'm':
+            prealloc = qapi_enum_parse(&PreallocMode_lookup, optarg,
+                                       PREALLOC_MODE__MAX, NULL);
+            if (prealloc == PREALLOC_MODE__MAX) {
+                error_report("Invalid preallocation mode '%s'", optarg);
+                return -EINVAL;
+            }
+            break;
+        default:
+            qemuio_command_usage(&truncate_cmd);
+            return -EINVAL;
+        }
+    }
+
+    offset = cvtnum(argv[optind]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[1]);
+        return offset;
+    }
+
+    /*
+     * qemu-io is a debugging tool, so let us be strict here and pass
+     * exact=true.  It is better to err on the "emit more errors" side
+     * than to be overly permissive.
+     */
+    ret = blk_truncate(blk, offset, false, prealloc, 0, &local_err);
+    if (ret < 0) {
+        error_report_err(local_err);
+        return ret;
+    }
+
+    return 0;
+}
+
+static int length_f(BlockBackend *blk, int argc, char **argv)
+{
+    int64_t size;
+    char s1[64];
+
+    size = blk_getlength(blk);
+    if (size < 0) {
+        printf("getlength: %s\n", strerror(-size));
+        return size;
+    }
+
+    cvtstr(size, s1, sizeof(s1));
+    printf("%s\n", s1);
+    return 0;
+}
+
+
+static const cmdinfo_t length_cmd = {
+    .name   = "length",
+    .altname    = "l",
+    .cfunc      = length_f,
+    .oneline    = "gets the length of the current file",
+};
+
+
+static int info_f(BlockBackend *blk, int argc, char **argv)
+{
+    BlockDriverState *bs = blk_bs(blk);
+    BlockDriverInfo bdi;
+    ImageInfoSpecific *spec_info;
+    Error *local_err = NULL;
+    char s1[64], s2[64];
+    int ret;
+
+    if (bs->drv && bs->drv->format_name) {
+        printf("format name: %s\n", bs->drv->format_name);
+    }
+    if (bs->drv && bs->drv->protocol_name) {
+        printf("format name: %s\n", bs->drv->protocol_name);
+    }
+
+    ret = bdrv_get_info(bs, &bdi);
+    if (ret) {
+        return ret;
+    }
+
+    cvtstr(bdi.cluster_size, s1, sizeof(s1));
+    cvtstr(bdi.vm_state_offset, s2, sizeof(s2));
+
+    printf("cluster size: %s\n", s1);
+    printf("vm state offset: %s\n", s2);
+
+    spec_info = bdrv_get_specific_info(bs, &local_err);
+    if (local_err) {
+        error_report_err(local_err);
+        return -EIO;
+    }
+    if (spec_info) {
+        printf("Format specific information:\n");
+        bdrv_image_info_specific_dump(spec_info);
+        qapi_free_ImageInfoSpecific(spec_info);
+    }
+
+    return 0;
+}
+
+
+
+static const cmdinfo_t info_cmd = {
+    .name       = "info",
+    .altname    = "i",
+    .cfunc      = info_f,
+    .oneline    = "prints information about the current file",
+};
+
+static void discard_help(void)
+{
+    printf(
+"\n"
+" discards a range of bytes from the given offset\n"
+"\n"
+" Example:\n"
+" 'discard 512 1k' - discards 1 kilobyte from 512 bytes into the file\n"
+"\n"
+" Discards a segment of the currently open file.\n"
+" -C, -- report statistics in a machine parsable format\n"
+" -q, -- quiet mode, do not show I/O statistics\n"
+"\n");
+}
+
+static int discard_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t discard_cmd = {
+    .name       = "discard",
+    .altname    = "d",
+    .cfunc      = discard_f,
+    .perm       = BLK_PERM_WRITE,
+    .argmin     = 2,
+    .argmax     = -1,
+    .args       = "[-Cq] off len",
+    .oneline    = "discards a number of bytes at a specified offset",
+    .help       = discard_help,
+};
+
+static int discard_f(BlockBackend *blk, int argc, char **argv)
+{
+    struct timespec t1, t2;
+    bool Cflag = false, qflag = false;
+    int c, ret;
+    int64_t offset, bytes;
+
+    while ((c = getopt(argc, argv, "Cq")) != -1) {
+        switch (c) {
+        case 'C':
+            Cflag = true;
+            break;
+        case 'q':
+            qflag = true;
+            break;
+        default:
+            qemuio_command_usage(&discard_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind != argc - 2) {
+        qemuio_command_usage(&discard_cmd);
+        return -EINVAL;
+    }
+
+    offset = cvtnum(argv[optind]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[optind]);
+        return offset;
+    }
+
+    optind++;
+    bytes = cvtnum(argv[optind]);
+    if (bytes < 0) {
+        print_cvtnum_err(bytes, argv[optind]);
+        return bytes;
+    } else if (bytes > BDRV_REQUEST_MAX_BYTES) {
+        printf("length cannot exceed %"PRIu64", given %s\n",
+               (uint64_t)BDRV_REQUEST_MAX_BYTES, argv[optind]);
+        return -EINVAL;
+    }
+
+    clock_gettime(CLOCK_MONOTONIC, &t1);
+    ret = blk_pdiscard(blk, offset, bytes);
+    clock_gettime(CLOCK_MONOTONIC, &t2);
+
+    if (ret < 0) {
+        printf("discard failed: %s\n", strerror(-ret));
+        return ret;
+    }
+
+    /* Finally, report back -- -C gives a parsable format */
+    if (!qflag) {
+        t2 = tsub(t2, t1);
+        print_report("discard", &t2, offset, bytes, bytes, 1, Cflag);
+    }
+
+    return 0;
+}
+
+static int alloc_f(BlockBackend *blk, int argc, char **argv)
+{
+    BlockDriverState *bs = blk_bs(blk);
+    int64_t offset, start, remaining, count;
+    char s1[64];
+    int ret;
+    int64_t num, sum_alloc;
+
+    start = offset = cvtnum(argv[1]);
+    if (offset < 0) {
+        print_cvtnum_err(offset, argv[1]);
+        return offset;
+    }
+
+    if (argc == 3) {
+        count = cvtnum(argv[2]);
+        if (count < 0) {
+            print_cvtnum_err(count, argv[2]);
+            return count;
+        }
+    } else {
+        count = BDRV_SECTOR_SIZE;
+    }
+
+    remaining = count;
+    sum_alloc = 0;
+    while (remaining) {
+        ret = bdrv_is_allocated(bs, offset, remaining, &num);
+        if (ret < 0) {
+            printf("is_allocated failed: %s\n", strerror(-ret));
+            return ret;
+        }
+        offset += num;
+        remaining -= num;
+        if (ret) {
+            sum_alloc += num;
+        }
+        if (num == 0) {
+            count -= remaining;
+            remaining = 0;
+        }
+    }
+
+    cvtstr(start, s1, sizeof(s1));
+
+    printf("%"PRId64"/%"PRId64" bytes allocated at offset %s\n",
+           sum_alloc, count, s1);
+    return 0;
+}
+
+static const cmdinfo_t alloc_cmd = {
+    .name       = "alloc",
+    .altname    = "a",
+    .argmin     = 1,
+    .argmax     = 2,
+    .cfunc      = alloc_f,
+    .args       = "offset [count]",
+    .oneline    = "checks if offset is allocated in the file",
+};
+
+
+static int map_is_allocated(BlockDriverState *bs, int64_t offset,
+                            int64_t bytes, int64_t *pnum)
+{
+    int64_t num;
+    int num_checked;
+    int ret, firstret;
+
+    num_checked = MIN(bytes, BDRV_REQUEST_MAX_BYTES);
+    ret = bdrv_is_allocated(bs, offset, num_checked, &num);
+    if (ret < 0) {
+        return ret;
+    }
+
+    firstret = ret;
+    *pnum = num;
+
+    while (bytes > 0 && ret == firstret) {
+        offset += num;
+        bytes -= num;
+
+        num_checked = MIN(bytes, BDRV_REQUEST_MAX_BYTES);
+        ret = bdrv_is_allocated(bs, offset, num_checked, &num);
+        if (ret == firstret && num) {
+            *pnum += num;
+        } else {
+            break;
+        }
+    }
+
+    return firstret;
+}
+
+static int map_f(BlockBackend *blk, int argc, char **argv)
+{
+    int64_t offset, bytes;
+    char s1[64], s2[64];
+    int64_t num;
+    int ret;
+    const char *retstr;
+
+    offset = 0;
+    bytes = blk_getlength(blk);
+    if (bytes < 0) {
+        error_report("Failed to query image length: %s", strerror(-bytes));
+        return bytes;
+    }
+
+    while (bytes) {
+        ret = map_is_allocated(blk_bs(blk), offset, bytes, &num);
+        if (ret < 0) {
+            error_report("Failed to get allocation status: %s", strerror(-ret));
+            return ret;
+        } else if (!num) {
+            error_report("Unexpected end of image");
+            return -EIO;
+        }
+
+        retstr = ret ? "    allocated" : "not allocated";
+        cvtstr(num, s1, sizeof(s1));
+        cvtstr(offset, s2, sizeof(s2));
+        printf("%s (0x%" PRIx64 ") bytes %s at offset %s (0x%" PRIx64 ")\n",
+               s1, num, retstr, s2, offset);
+
+        offset += num;
+        bytes -= num;
+    }
+
+    return 0;
+}
+
+static const cmdinfo_t map_cmd = {
+       .name           = "map",
+       .argmin         = 0,
+       .argmax         = 0,
+       .cfunc          = map_f,
+       .args           = "",
+       .oneline        = "prints the allocated areas of a file",
+};
+
+static void reopen_help(void)
+{
+    printf(
+"\n"
+" Changes the open options of an already opened image\n"
+"\n"
+" Example:\n"
+" 'reopen -o lazy-refcounts=on' - activates lazy refcount writeback on a qcow2 image\n"
+"\n"
+" -r, -- Reopen the image read-only\n"
+" -w, -- Reopen the image read-write\n"
+" -c, -- Change the cache mode to the given value\n"
+" -o, -- Changes block driver options (cf. 'open' command)\n"
+"\n");
+}
+
+static int reopen_f(BlockBackend *blk, int argc, char **argv);
+
+static QemuOptsList reopen_opts = {
+    .name = "reopen",
+    .merge_lists = true,
+    .head = QTAILQ_HEAD_INITIALIZER(reopen_opts.head),
+    .desc = {
+        /* no elements => accept any params */
+        { /* end of list */ }
+    },
+};
+
+static const cmdinfo_t reopen_cmd = {
+       .name           = "reopen",
+       .argmin         = 0,
+       .argmax         = -1,
+       .cfunc          = reopen_f,
+       .args           = "[(-r|-w)] [-c cache] [-o options]",
+       .oneline        = "reopens an image with new options",
+       .help           = reopen_help,
+};
+
+static int reopen_f(BlockBackend *blk, int argc, char **argv)
+{
+    BlockDriverState *bs = blk_bs(blk);
+    QemuOpts *qopts;
+    QDict *opts;
+    int c;
+    int flags = bs->open_flags;
+    bool writethrough = !blk_enable_write_cache(blk);
+    bool has_rw_option = false;
+    bool has_cache_option = false;
+    Error *local_err = NULL;
+
+    while ((c = getopt(argc, argv, "c:o:rw")) != -1) {
+        switch (c) {
+        case 'c':
+            if (bdrv_parse_cache_mode(optarg, &flags, &writethrough) < 0) {
+                error_report("Invalid cache option: %s", optarg);
+                return -EINVAL;
+            }
+            has_cache_option = true;
+            break;
+        case 'o':
+            if (!qemu_opts_parse_noisily(&reopen_opts, optarg, 0)) {
+                qemu_opts_reset(&reopen_opts);
+                return -EINVAL;
+            }
+            break;
+        case 'r':
+            if (has_rw_option) {
+                error_report("Only one -r/-w option may be given");
+                return -EINVAL;
+            }
+            flags &= ~BDRV_O_RDWR;
+            has_rw_option = true;
+            break;
+        case 'w':
+            if (has_rw_option) {
+                error_report("Only one -r/-w option may be given");
+                return -EINVAL;
+            }
+            flags |= BDRV_O_RDWR;
+            has_rw_option = true;
+            break;
+        default:
+            qemu_opts_reset(&reopen_opts);
+            qemuio_command_usage(&reopen_cmd);
+            return -EINVAL;
+        }
+    }
+
+    if (optind != argc) {
+        qemu_opts_reset(&reopen_opts);
+        qemuio_command_usage(&reopen_cmd);
+        return -EINVAL;
+    }
+
+    if (!writethrough != blk_enable_write_cache(blk) &&
+        blk_get_attached_dev(blk))
+    {
+        error_report("Cannot change cache.writeback: Device attached");
+        qemu_opts_reset(&reopen_opts);
+        return -EBUSY;
+    }
+
+    if (!(flags & BDRV_O_RDWR)) {
+        uint64_t orig_perm, orig_shared_perm;
+
+        bdrv_drain(bs);
+
+        blk_get_perm(blk, &orig_perm, &orig_shared_perm);
+        blk_set_perm(blk,
+                     orig_perm & ~(BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED),
+                     orig_shared_perm,
+                     &error_abort);
+    }
+
+    qopts = qemu_opts_find(&reopen_opts, NULL);
+    opts = qopts ? qemu_opts_to_qdict(qopts, NULL) : qdict_new();
+    qemu_opts_reset(&reopen_opts);
+
+    if (qdict_haskey(opts, BDRV_OPT_READ_ONLY)) {
+        if (has_rw_option) {
+            error_report("Cannot set both -r/-w and '" BDRV_OPT_READ_ONLY "'");
+            qobject_unref(opts);
+            return -EINVAL;
+        }
+    } else {
+        qdict_put_bool(opts, BDRV_OPT_READ_ONLY, !(flags & BDRV_O_RDWR));
+    }
+
+    if (qdict_haskey(opts, BDRV_OPT_CACHE_DIRECT) ||
+        qdict_haskey(opts, BDRV_OPT_CACHE_NO_FLUSH)) {
+        if (has_cache_option) {
+            error_report("Cannot set both -c and the cache options");
+            qobject_unref(opts);
+            return -EINVAL;
+        }
+    } else {
+        qdict_put_bool(opts, BDRV_OPT_CACHE_DIRECT, flags & BDRV_O_NOCACHE);
+        qdict_put_bool(opts, BDRV_OPT_CACHE_NO_FLUSH, flags & BDRV_O_NO_FLUSH);
+    }
+
+    bdrv_reopen(bs, opts, true, &local_err);
+
+    if (local_err) {
+        error_report_err(local_err);
+        return -EINVAL;
+    }
+
+    blk_set_enable_write_cache(blk, !writethrough);
+    return 0;
+}
+
+static int break_f(BlockBackend *blk, int argc, char **argv)
+{
+    int ret;
+
+    ret = bdrv_debug_breakpoint(blk_bs(blk), argv[1], argv[2]);
+    if (ret < 0) {
+        printf("Could not set breakpoint: %s\n", strerror(-ret));
+        return ret;
+    }
+
+    return 0;
+}
+
+static int remove_break_f(BlockBackend *blk, int argc, char **argv)
+{
+    int ret;
+
+    ret = bdrv_debug_remove_breakpoint(blk_bs(blk), argv[1]);
+    if (ret < 0) {
+        printf("Could not remove breakpoint %s: %s\n", argv[1], strerror(-ret));
+        return ret;
+    }
+
+    return 0;
+}
+
+static const cmdinfo_t break_cmd = {
+       .name           = "break",
+       .argmin         = 2,
+       .argmax         = 2,
+       .cfunc          = break_f,
+       .args           = "event tag",
+       .oneline        = "sets a breakpoint on event and tags the stopped "
+                         "request as tag",
+};
+
+static const cmdinfo_t remove_break_cmd = {
+       .name           = "remove_break",
+       .argmin         = 1,
+       .argmax         = 1,
+       .cfunc          = remove_break_f,
+       .args           = "tag",
+       .oneline        = "remove a breakpoint by tag",
+};
+
+static int resume_f(BlockBackend *blk, int argc, char **argv)
+{
+    int ret;
+
+    ret = bdrv_debug_resume(blk_bs(blk), argv[1]);
+    if (ret < 0) {
+        printf("Could not resume request: %s\n", strerror(-ret));
+        return ret;
+    }
+
+    return 0;
+}
+
+static const cmdinfo_t resume_cmd = {
+       .name           = "resume",
+       .argmin         = 1,
+       .argmax         = 1,
+       .cfunc          = resume_f,
+       .args           = "tag",
+       .oneline        = "resumes the request tagged as tag",
+};
+
+static int wait_break_f(BlockBackend *blk, int argc, char **argv)
+{
+    while (!bdrv_debug_is_suspended(blk_bs(blk), argv[1])) {
+        aio_poll(blk_get_aio_context(blk), true);
+    }
+    return 0;
+}
+
+static const cmdinfo_t wait_break_cmd = {
+       .name           = "wait_break",
+       .argmin         = 1,
+       .argmax         = 1,
+       .cfunc          = wait_break_f,
+       .args           = "tag",
+       .oneline        = "waits for the suspension of a request",
+};
+
+static int abort_f(BlockBackend *blk, int argc, char **argv)
+{
+    abort();
+}
+
+static const cmdinfo_t abort_cmd = {
+       .name           = "abort",
+       .cfunc          = abort_f,
+       .flags          = CMD_NOFILE_OK,
+       .oneline        = "simulate a program crash using abort(3)",
+};
+
+static void sigraise_help(void)
+{
+    printf(
+"\n"
+" raises the given signal\n"
+"\n"
+" Example:\n"
+" 'sigraise %i' - raises SIGTERM\n"
+"\n"
+" Invokes raise(signal), where \"signal\" is the mandatory integer argument\n"
+" given to sigraise.\n"
+"\n", SIGTERM);
+}
+
+static int sigraise_f(BlockBackend *blk, int argc, char **argv);
+
+static const cmdinfo_t sigraise_cmd = {
+    .name       = "sigraise",
+    .cfunc      = sigraise_f,
+    .argmin     = 1,
+    .argmax     = 1,
+    .flags      = CMD_NOFILE_OK,
+    .args       = "signal",
+    .oneline    = "raises a signal",
+    .help       = sigraise_help,
+};
+
+static int sigraise_f(BlockBackend *blk, int argc, char **argv)
+{
+    int64_t sig = cvtnum(argv[1]);
+    if (sig < 0) {
+        print_cvtnum_err(sig, argv[1]);
+        return sig;
+    } else if (sig > NSIG) {
+        printf("signal argument '%s' is too large to be a valid signal\n",
+               argv[1]);
+        return -EINVAL;
+    }
+
+    /* Using raise() to kill this process does not necessarily flush all open
+     * streams. At least stdout and stderr (although the latter should be
+     * non-buffered anyway) should be flushed, though. */
+    fflush(stdout);
+    fflush(stderr);
+
+    raise(sig);
+
+    return 0;
+}
+
+static void sleep_cb(void *opaque)
+{
+    bool *expired = opaque;
+    *expired = true;
+}
+
+static int sleep_f(BlockBackend *blk, int argc, char **argv)
+{
+    char *endptr;
+    long ms;
+    struct QEMUTimer *timer;
+    bool expired = false;
+
+    ms = strtol(argv[1], &endptr, 0);
+    if (ms < 0 || *endptr != '\0') {
+        printf("%s is not a valid number\n", argv[1]);
+        return -EINVAL;
+    }
+
+    timer = timer_new_ns(QEMU_CLOCK_HOST, sleep_cb, &expired);
+    timer_mod(timer, qemu_clock_get_ns(QEMU_CLOCK_HOST) + SCALE_MS * ms);
+
+    while (!expired) {
+        main_loop_wait(false);
+    }
+
+    timer_free(timer);
+    return 0;
+}
+
+static const cmdinfo_t sleep_cmd = {
+       .name           = "sleep",
+       .argmin         = 1,
+       .argmax         = 1,
+       .cfunc          = sleep_f,
+       .flags          = CMD_NOFILE_OK,
+       .oneline        = "waits for the given value in milliseconds",
+};
+
+static void help_oneline(const char *cmd, const cmdinfo_t *ct)
+{
+    printf("%s ", cmd);
+
+    if (ct->args) {
+        printf("%s ", ct->args);
+    }
+    printf("-- %s\n", ct->oneline);
+}
+
+static void help_onecmd(const char *cmd, const cmdinfo_t *ct)
+{
+    help_oneline(cmd, ct);
+    if (ct->help) {
+        ct->help();
+    }
+}
+
+static void help_all(void)
+{
+    const cmdinfo_t *ct;
+
+    for (ct = cmdtab; ct < &cmdtab[ncmds]; ct++) {
+        help_oneline(ct->name, ct);
+    }
+    printf("\nUse 'help commandname' for extended help.\n");
+}
+
+static int help_f(BlockBackend *blk, int argc, char **argv)
+{
+    const cmdinfo_t *ct;
+
+    if (argc < 2) {
+        help_all();
+        return 0;
+    }
+
+    ct = find_command(argv[1]);
+    if (ct == NULL) {
+        printf("command %s not found\n", argv[1]);
+        return -EINVAL;
+    }
+
+    help_onecmd(argv[1], ct);
+    return 0;
+}
+
+static const cmdinfo_t help_cmd = {
+    .name       = "help",
+    .altname    = "?",
+    .cfunc      = help_f,
+    .argmin     = 0,
+    .argmax     = 1,
+    .flags      = CMD_FLAG_GLOBAL,
+    .args       = "[command]",
+    .oneline    = "help for one or all commands",
+};
+
+/*
+ * Called with aio context of blk acquired. Or with qemu_get_aio_context()
+ * context acquired if blk is NULL.
+ */
+int qemuio_command(BlockBackend *blk, const char *cmd)
+{
+    char *input;
+    const cmdinfo_t *ct;
+    char **v;
+    int c;
+    int ret = 0;
+
+    input = g_strdup(cmd);
+    v = breakline(input, &c);
+    if (c) {
+        ct = find_command(v[0]);
+        if (ct) {
+            ret = command(blk, ct, c, v);
+        } else {
+            fprintf(stderr, "command \"%s\" not found\n", v[0]);
+            ret = -EINVAL;
+        }
+    }
+    g_free(input);
+    g_free(v);
+
+    return ret;
+}
+
+static void __attribute((constructor)) init_qemuio_commands(void)
+{
+    /* initialize commands */
+    qemuio_add_command(&help_cmd);
+    qemuio_add_command(&read_cmd);
+    qemuio_add_command(&readv_cmd);
+    qemuio_add_command(&write_cmd);
+    qemuio_add_command(&writev_cmd);
+    qemuio_add_command(&aio_read_cmd);
+    qemuio_add_command(&aio_write_cmd);
+    qemuio_add_command(&aio_flush_cmd);
+    qemuio_add_command(&flush_cmd);
+    qemuio_add_command(&truncate_cmd);
+    qemuio_add_command(&length_cmd);
+    qemuio_add_command(&info_cmd);
+    qemuio_add_command(&discard_cmd);
+    qemuio_add_command(&alloc_cmd);
+    qemuio_add_command(&map_cmd);
+    qemuio_add_command(&reopen_cmd);
+    qemuio_add_command(&break_cmd);
+    qemuio_add_command(&remove_break_cmd);
+    qemuio_add_command(&resume_cmd);
+    qemuio_add_command(&wait_break_cmd);
+    qemuio_add_command(&abort_cmd);
+    qemuio_add_command(&sleep_cmd);
+    qemuio_add_command(&sigraise_cmd);
+}