Merge remote-tracking branch 'stefanha/block' into staging

* stefanha/block:
  rbd: add an asynchronous flush
  iotests: Add 'check -ssh' option to test Secure Shell block device.
  block: ssh: Use libssh2_sftp_fsync (if supported by libssh2) to flush to disk.
  block: Add support for Secure Shell (ssh) block device.
  ide: refuse WIN_READ_NATIVE_MAX on empty device
  qemu-iotests: filter QEMU_PROG in 051.out
  qemu-iotests: Add test for -drive options
  qemu-iotests: A few more bdrv_pread/pwrite tests
  block: Introduce bdrv_pwritev() for qcow2_save_vmstate
  savevm: Implement block_writev_buffer()
  block: Introduce bdrv_writev_vmstate

Conflicts:
	savevm.c

aliguori: add f->pos parameter to writev_buffer().

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

22 files changed, 1722 insertions, 44 deletions

diff --git a/block.c b/block.c
index 602d8a443e..4ad663d3fa 100644
--- a/block.c
+++ b/block.c
@@ -2131,27 +2131,21 @@ static void coroutine_fn bdrv_rw_co_entry(void *opaque)
 }
 
 /*
- * Process a synchronous request using coroutines
+ * Process a vectored synchronous request using coroutines
  */
-static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
-                      int nb_sectors, bool is_write)
+static int bdrv_rwv_co(BlockDriverState *bs, int64_t sector_num,
+                       QEMUIOVector *qiov, bool is_write)
 {
-    QEMUIOVector qiov;
-    struct iovec iov = {
-        .iov_base = (void *)buf,
-        .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
-    };
     Coroutine *co;
     RwCo rwco = {
         .bs = bs,
         .sector_num = sector_num,
-        .nb_sectors = nb_sectors,
-        .qiov = &qiov,
+        .nb_sectors = qiov->size >> BDRV_SECTOR_BITS,
+        .qiov = qiov,
         .is_write = is_write,
         .ret = NOT_DONE,
     };
-
-    qemu_iovec_init_external(&qiov, &iov, 1);
+    assert((qiov->size & (BDRV_SECTOR_SIZE - 1)) == 0);
 
     /**
      * In sync call context, when the vcpu is blocked, this throttling timer
@@ -2177,6 +2171,22 @@ static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
     return rwco.ret;
 }
 
+/*
+ * Process a synchronous request using coroutines
+ */
+static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
+                      int nb_sectors, bool is_write)
+{
+    QEMUIOVector qiov;
+    struct iovec iov = {
+        .iov_base = (void *)buf,
+        .iov_len = nb_sectors * BDRV_SECTOR_SIZE,
+    };
+
+    qemu_iovec_init_external(&qiov, &iov, 1);
+    return bdrv_rwv_co(bs, sector_num, &qiov, is_write);
+}
+
 /* return < 0 if error. See bdrv_write() for the return codes */
 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors)
@@ -2210,6 +2220,11 @@ int bdrv_write(BlockDriverState *bs, int64_t sector_num,
     return bdrv_rw_co(bs, sector_num, (uint8_t *)buf, nb_sectors, true);
 }
 
+int bdrv_writev(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov)
+{
+    return bdrv_rwv_co(bs, sector_num, qiov, true);
+}
+
 int bdrv_pread(BlockDriverState *bs, int64_t offset,
                void *buf, int count1)
 {
@@ -2255,15 +2270,15 @@ int bdrv_pread(BlockDriverState *bs, int64_t offset,
     return count1;
 }
 
-int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
-                const void *buf, int count1)
+int bdrv_pwritev(BlockDriverState *bs, int64_t offset, QEMUIOVector *qiov)
 {
     uint8_t tmp_buf[BDRV_SECTOR_SIZE];
     int len, nb_sectors, count;
     int64_t sector_num;
     int ret;
 
-    count = count1;
+    count = qiov->size;
+
     /* first write to align to sector start */
     len = (BDRV_SECTOR_SIZE - offset) & (BDRV_SECTOR_SIZE - 1);
     if (len > count)
@@ -2272,24 +2287,32 @@ int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
     if (len > 0) {
         if ((ret = bdrv_read(bs, sector_num, tmp_buf, 1)) < 0)
             return ret;
-        memcpy(tmp_buf + (offset & (BDRV_SECTOR_SIZE - 1)), buf, len);
+        qemu_iovec_to_buf(qiov, 0, tmp_buf + (offset & (BDRV_SECTOR_SIZE - 1)),
+                          len);
         if ((ret = bdrv_write(bs, sector_num, tmp_buf, 1)) < 0)
             return ret;
         count -= len;
         if (count == 0)
-            return count1;
+            return qiov->size;
         sector_num++;
-        buf += len;
     }
 
     /* write the sectors "in place" */
     nb_sectors = count >> BDRV_SECTOR_BITS;
     if (nb_sectors > 0) {
-        if ((ret = bdrv_write(bs, sector_num, buf, nb_sectors)) < 0)
+        QEMUIOVector qiov_inplace;
+
+        qemu_iovec_init(&qiov_inplace, qiov->niov);
+        qemu_iovec_concat(&qiov_inplace, qiov, len,
+                          nb_sectors << BDRV_SECTOR_BITS);
+        ret = bdrv_writev(bs, sector_num, &qiov_inplace);
+        qemu_iovec_destroy(&qiov_inplace);
+        if (ret < 0) {
             return ret;
+        }
+
         sector_num += nb_sectors;
         len = nb_sectors << BDRV_SECTOR_BITS;
-        buf += len;
         count -= len;
     }
 
@@ -2297,11 +2320,24 @@ int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
     if (count > 0) {
         if ((ret = bdrv_read(bs, sector_num, tmp_buf, 1)) < 0)
             return ret;
-        memcpy(tmp_buf, buf, count);
+        qemu_iovec_to_buf(qiov, qiov->size - count, tmp_buf, count);
         if ((ret = bdrv_write(bs, sector_num, tmp_buf, 1)) < 0)
             return ret;
     }
-    return count1;
+    return qiov->size;
+}
+
+int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
+                const void *buf, int count1)
+{
+    QEMUIOVector qiov;
+    struct iovec iov = {
+        .iov_base   = (void *) buf,
+        .iov_len    = count1,
+    };
+
+    qemu_iovec_init_external(&qiov, &iov, 1);
+    return bdrv_pwritev(bs, offset, &qiov);
 }
 
 /*
@@ -3184,13 +3220,28 @@ int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
 int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
                       int64_t pos, int size)
 {
+    QEMUIOVector qiov;
+    struct iovec iov = {
+        .iov_base   = (void *) buf,
+        .iov_len    = size,
+    };
+
+    qemu_iovec_init_external(&qiov, &iov, 1);
+    return bdrv_writev_vmstate(bs, &qiov, pos);
+}
+
+int bdrv_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos)
+{
     BlockDriver *drv = bs->drv;
-    if (!drv)
+
+    if (!drv) {
         return -ENOMEDIUM;
-    if (drv->bdrv_save_vmstate)
-        return drv->bdrv_save_vmstate(bs, buf, pos, size);
-    if (bs->file)
-        return bdrv_save_vmstate(bs->file, buf, pos, size);
+    } else if (drv->bdrv_save_vmstate) {
+        return drv->bdrv_save_vmstate(bs, qiov, pos);
+    } else if (bs->file) {
+        return bdrv_writev_vmstate(bs->file, qiov, pos);
+    }
+
     return -ENOTSUP;
 }
 
diff --git a/block/Makefile.objs b/block/Makefile.objs
index c067f38e1d..6c4b5bc6b0 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -13,6 +13,7 @@ block-obj-$(CONFIG_LIBISCSI) += iscsi.o
 block-obj-$(CONFIG_CURL) += curl.o
 block-obj-$(CONFIG_RBD) += rbd.o
 block-obj-$(CONFIG_GLUSTERFS) += gluster.o
+block-obj-$(CONFIG_LIBSSH2) += ssh.o
 endif
 
 common-obj-y += stream.o
diff --git a/block/qcow2.c b/block/qcow2.c
index 1d180732e9..e8934de185 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -1652,8 +1652,8 @@ static void dump_refcounts(BlockDriverState *bs)
 }
 #endif
 
-static int qcow2_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
-                              int64_t pos, int size)
+static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
+                              int64_t pos)
 {
     BDRVQcowState *s = bs->opaque;
     int growable = bs->growable;
@@ -1661,7 +1661,7 @@ static int qcow2_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
 
     BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
     bs->growable = 1;
-    ret = bdrv_pwrite(bs, qcow2_vm_state_offset(s) + pos, buf, size);
+    ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
     bs->growable = growable;
 
     return ret;
diff --git a/block/rbd.c b/block/rbd.c
index 1a8ea6d492..141b488968 100644
--- a/block/rbd.c
+++ b/block/rbd.c
@@ -63,7 +63,8 @@
 typedef enum {
     RBD_AIO_READ,
     RBD_AIO_WRITE,
-    RBD_AIO_DISCARD
+    RBD_AIO_DISCARD,
+    RBD_AIO_FLUSH
 } RBDAIOCmd;
 
 typedef struct RBDAIOCB {
@@ -379,8 +380,7 @@ static void qemu_rbd_complete_aio(RADOSCB *rcb)
 
     r = rcb->ret;
 
-    if (acb->cmd == RBD_AIO_WRITE ||
-        acb->cmd == RBD_AIO_DISCARD) {
+    if (acb->cmd != RBD_AIO_READ) {
         if (r < 0) {
             acb->ret = r;
             acb->error = 1;
@@ -659,6 +659,16 @@ static int rbd_aio_discard_wrapper(rbd_image_t image,
 #endif
 }
 
+static int rbd_aio_flush_wrapper(rbd_image_t image,
+                                 rbd_completion_t comp)
+{
+#ifdef LIBRBD_SUPPORTS_AIO_FLUSH
+    return rbd_aio_flush(image, comp);
+#else
+    return -ENOTSUP;
+#endif
+}
+
 static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
                                        int64_t sector_num,
                                        QEMUIOVector *qiov,
@@ -679,7 +689,7 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
     acb = qemu_aio_get(&rbd_aiocb_info, bs, cb, opaque);
     acb->cmd = cmd;
     acb->qiov = qiov;
-    if (cmd == RBD_AIO_DISCARD) {
+    if (cmd == RBD_AIO_DISCARD || cmd == RBD_AIO_FLUSH) {
         acb->bounce = NULL;
     } else {
         acb->bounce = qemu_blockalign(bs, qiov->size);
@@ -723,6 +733,9 @@ static BlockDriverAIOCB *rbd_start_aio(BlockDriverState *bs,
     case RBD_AIO_DISCARD:
         r = rbd_aio_discard_wrapper(s->image, off, size, c);
         break;
+    case RBD_AIO_FLUSH:
+        r = rbd_aio_flush_wrapper(s->image, c);
+        break;
     default:
         r = -EINVAL;
     }
@@ -762,6 +775,16 @@ static BlockDriverAIOCB *qemu_rbd_aio_writev(BlockDriverState *bs,
                          RBD_AIO_WRITE);
 }
 
+#ifdef LIBRBD_SUPPORTS_AIO_FLUSH
+static BlockDriverAIOCB *qemu_rbd_aio_flush(BlockDriverState *bs,
+                                            BlockDriverCompletionFunc *cb,
+                                            void *opaque)
+{
+    return rbd_start_aio(bs, 0, NULL, 0, cb, opaque, RBD_AIO_FLUSH);
+}
+
+#else
+
 static int qemu_rbd_co_flush(BlockDriverState *bs)
 {
 #if LIBRBD_VERSION_CODE >= LIBRBD_VERSION(0, 1, 1)
@@ -772,6 +795,7 @@ static int qemu_rbd_co_flush(BlockDriverState *bs)
     return 0;
 #endif
 }
+#endif
 
 static int qemu_rbd_getinfo(BlockDriverState *bs, BlockDriverInfo *bdi)
 {
@@ -949,7 +973,12 @@ static BlockDriver bdrv_rbd = {
 
     .bdrv_aio_readv         = qemu_rbd_aio_readv,
     .bdrv_aio_writev        = qemu_rbd_aio_writev,
+
+#ifdef LIBRBD_SUPPORTS_AIO_FLUSH
+    .bdrv_aio_flush         = qemu_rbd_aio_flush,
+#else
     .bdrv_co_flush_to_disk  = qemu_rbd_co_flush,
+#endif
 
 #ifdef LIBRBD_SUPPORTS_DISCARD
     .bdrv_aio_discard       = qemu_rbd_aio_discard,
diff --git a/block/sheepdog.c b/block/sheepdog.c
index 987018e20c..1c5b53220b 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2054,12 +2054,19 @@ cleanup:
     return ret;
 }
 
-static int sd_save_vmstate(BlockDriverState *bs, const uint8_t *data,
-                           int64_t pos, int size)
+static int sd_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
+                           int64_t pos)
 {
     BDRVSheepdogState *s = bs->opaque;
+    void *buf;
+    int ret;
 
-    return do_load_save_vmstate(s, (uint8_t *)data, pos, size, 0);
+    buf = qemu_blockalign(bs, qiov->size);
+    qemu_iovec_to_buf(qiov, 0, buf, qiov->size);
+    ret = do_load_save_vmstate(s, (uint8_t *) buf, pos, qiov->size, 0);
+    qemu_vfree(buf);
+
+    return ret;
 }
 
 static int sd_load_vmstate(BlockDriverState *bs, uint8_t *data,
diff --git a/block/ssh.c b/block/ssh.c
new file mode 100644
index 0000000000..8f78e2e4b9
--- /dev/null
+++ b/block/ssh.c
@@ -0,0 +1,1063 @@
+/*
+ * Secure Shell (ssh) backend for QEMU.
+ *
+ * Copyright (C) 2013 Red Hat Inc., Richard W.M. Jones <rjones@redhat.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+
+#include <libssh2.h>
+#include <libssh2_sftp.h>
+
+#include "block/block_int.h"
+#include "qemu/sockets.h"
+#include "qemu/uri.h"
+#include "qapi/qmp/qint.h"
+
+/* DEBUG_SSH=1 enables the DPRINTF (debugging printf) statements in
+ * this block driver code.
+ *
+ * TRACE_LIBSSH2=<bitmask> enables tracing in libssh2 itself.  Note
+ * that this requires that libssh2 was specially compiled with the
+ * `./configure --enable-debug' option, so most likely you will have
+ * to compile it yourself.  The meaning of <bitmask> is described
+ * here: http://www.libssh2.org/libssh2_trace.html
+ */
+#define DEBUG_SSH     0
+#define TRACE_LIBSSH2 0 /* or try: LIBSSH2_TRACE_SFTP */
+
+#define DPRINTF(fmt, ...)                           \
+    do {                                            \
+        if (DEBUG_SSH) {                            \
+            fprintf(stderr, "ssh: %-15s " fmt "\n", \
+                    __func__, ##__VA_ARGS__);       \
+        }                                           \
+    } while (0)
+
+typedef struct BDRVSSHState {
+    /* Coroutine. */
+    CoMutex lock;
+
+    /* SSH connection. */
+    int sock;                         /* socket */
+    LIBSSH2_SESSION *session;         /* ssh session */
+    LIBSSH2_SFTP *sftp;               /* sftp session */
+    LIBSSH2_SFTP_HANDLE *sftp_handle; /* sftp remote file handle */
+
+    /* See ssh_seek() function below. */
+    int64_t offset;
+    bool offset_op_read;
+
+    /* File attributes at open.  We try to keep the .filesize field
+     * updated if it changes (eg by writing at the end of the file).
+     */
+    LIBSSH2_SFTP_ATTRIBUTES attrs;
+
+    /* Used to warn if 'flush' is not supported. */
+    char *hostport;
+    bool unsafe_flush_warning;
+} BDRVSSHState;
+
+static void ssh_state_init(BDRVSSHState *s)
+{
+    memset(s, 0, sizeof *s);
+    s->sock = -1;
+    s->offset = -1;
+    qemu_co_mutex_init(&s->lock);
+}
+
+static void ssh_state_free(BDRVSSHState *s)
+{
+    g_free(s->hostport);
+    if (s->sftp_handle) {
+        libssh2_sftp_close(s->sftp_handle);
+    }
+    if (s->sftp) {
+        libssh2_sftp_shutdown(s->sftp);
+    }
+    if (s->session) {
+        libssh2_session_disconnect(s->session,
+                                   "from qemu ssh client: "
+                                   "user closed the connection");
+        libssh2_session_free(s->session);
+    }
+    if (s->sock >= 0) {
+        close(s->sock);
+    }
+}
+
+/* Wrappers around error_report which make sure to dump as much
+ * information from libssh2 as possible.
+ */
+static void
+session_error_report(BDRVSSHState *s, const char *fs, ...)
+{
+    va_list args;
+
+    va_start(args, fs);
+    error_vprintf(fs, args);
+
+    if ((s)->session) {
+        char *ssh_err;
+        int ssh_err_code;
+
+        libssh2_session_last_error((s)->session, &ssh_err, NULL, 0);
+        /* This is not an errno.  See <libssh2.h>. */
+        ssh_err_code = libssh2_session_last_errno((s)->session);
+
+        error_printf(": %s (libssh2 error code: %d)", ssh_err, ssh_err_code);
+    }
+
+    va_end(args);
+    error_printf("\n");
+}
+
+static void
+sftp_error_report(BDRVSSHState *s, const char *fs, ...)
+{
+    va_list args;
+
+    va_start(args, fs);
+    error_vprintf(fs, args);
+
+    if ((s)->sftp) {
+        char *ssh_err;
+        int ssh_err_code;
+        unsigned long sftp_err_code;
+
+        libssh2_session_last_error((s)->session, &ssh_err, NULL, 0);
+        /* This is not an errno.  See <libssh2.h>. */
+        ssh_err_code = libssh2_session_last_errno((s)->session);
+        /* See <libssh2_sftp.h>. */
+        sftp_err_code = libssh2_sftp_last_error((s)->sftp);
+
+        error_printf(": %s (libssh2 error code: %d, sftp error code: %lu)",
+                     ssh_err, ssh_err_code, sftp_err_code);
+    }
+
+    va_end(args);
+    error_printf("\n");
+}
+
+static int parse_uri(const char *filename, QDict *options, Error **errp)
+{
+    URI *uri = NULL;
+    QueryParams *qp = NULL;
+    int i;
+
+    uri = uri_parse(filename);
+    if (!uri) {
+        return -EINVAL;
+    }
+
+    if (strcmp(uri->scheme, "ssh") != 0) {
+        error_setg(errp, "URI scheme must be 'ssh'");
+        goto err;
+    }
+
+    if (!uri->server || strcmp(uri->server, "") == 0) {
+        error_setg(errp, "missing hostname in URI");
+        goto err;
+    }
+
+    if (!uri->path || strcmp(uri->path, "") == 0) {
+        error_setg(errp, "missing remote path in URI");
+        goto err;
+    }
+
+    qp = query_params_parse(uri->query);
+    if (!qp) {
+        error_setg(errp, "could not parse query parameters");
+        goto err;
+    }
+
+    if(uri->user && strcmp(uri->user, "") != 0) {
+        qdict_put(options, "user", qstring_from_str(uri->user));
+    }
+
+    qdict_put(options, "host", qstring_from_str(uri->server));
+
+    if (uri->port) {
+        qdict_put(options, "port", qint_from_int(uri->port));
+    }
+
+    qdict_put(options, "path", qstring_from_str(uri->path));
+
+    /* Pick out any query parameters that we understand, and ignore
+     * the rest.
+     */
+    for (i = 0; i < qp->n; ++i) {
+        if (strcmp(qp->p[i].name, "host_key_check") == 0) {
+            qdict_put(options, "host_key_check",
+                      qstring_from_str(qp->p[i].value));
+        }
+    }
+
+    query_params_free(qp);
+    uri_free(uri);
+    return 0;
+
+ err:
+    if (qp) {
+      query_params_free(qp);
+    }
+    if (uri) {
+      uri_free(uri);
+    }
+    return -EINVAL;
+}
+
+static void ssh_parse_filename(const char *filename, QDict *options,
+                               Error **errp)
+{
+    if (qdict_haskey(options, "user") ||
+        qdict_haskey(options, "host") ||
+        qdict_haskey(options, "port") ||
+        qdict_haskey(options, "path") ||
+        qdict_haskey(options, "host_key_check")) {
+        error_setg(errp, "user, host, port, path, host_key_check cannot be used at the same time as a file option");
+        return;
+    }
+
+    parse_uri(filename, options, errp);
+}
+
+static int check_host_key_knownhosts(BDRVSSHState *s,
+                                     const char *host, int port)
+{
+    const char *home;
+    char *knh_file = NULL;
+    LIBSSH2_KNOWNHOSTS *knh = NULL;
+    struct libssh2_knownhost *found;
+    int ret, r;
+    const char *hostkey;
+    size_t len;
+    int type;
+
+    hostkey = libssh2_session_hostkey(s->session, &len, &type);
+    if (!hostkey) {
+        ret = -EINVAL;
+        session_error_report(s, "failed to read remote host key");
+        goto out;
+    }
+
+    knh = libssh2_knownhost_init(s->session);
+    if (!knh) {
+        ret = -EINVAL;
+        session_error_report(s, "failed to initialize known hosts support");
+        goto out;
+    }
+
+    home = getenv("HOME");
+    if (home) {
+        knh_file = g_strdup_printf("%s/.ssh/known_hosts", home);
+    } else {
+        knh_file = g_strdup_printf("/root/.ssh/known_hosts");
+    }
+
+    /* Read all known hosts from OpenSSH-style known_hosts file. */
+    libssh2_knownhost_readfile(knh, knh_file, LIBSSH2_KNOWNHOST_FILE_OPENSSH);
+
+    r = libssh2_knownhost_checkp(knh, host, port, hostkey, len,
+                                 LIBSSH2_KNOWNHOST_TYPE_PLAIN|
+                                 LIBSSH2_KNOWNHOST_KEYENC_RAW,
+                                 &found);
+    switch (r) {
+    case LIBSSH2_KNOWNHOST_CHECK_MATCH:
+        /* OK */
+        DPRINTF("host key OK: %s", found->key);
+        break;
+    case LIBSSH2_KNOWNHOST_CHECK_MISMATCH:
+        ret = -EINVAL;
+        session_error_report(s, "host key does not match the one in known_hosts (found key %s)",
+                             found->key);
+        goto out;
+    case LIBSSH2_KNOWNHOST_CHECK_NOTFOUND:
+        ret = -EINVAL;
+        session_error_report(s, "no host key was found in known_hosts");
+        goto out;
+    case LIBSSH2_KNOWNHOST_CHECK_FAILURE:
+        ret = -EINVAL;
+        session_error_report(s, "failure matching the host key with known_hosts");
+        goto out;
+    default:
+        ret = -EINVAL;
+        session_error_report(s, "unknown error matching the host key with known_hosts (%d)",
+                             r);
+        goto out;
+    }
+
+    /* known_hosts checking successful. */
+    ret = 0;
+
+ out:
+    if (knh != NULL) {
+        libssh2_knownhost_free(knh);
+    }
+    g_free(knh_file);
+    return ret;
+}
+
+static unsigned hex2decimal(char ch)
+{
+    if (ch >= '0' && ch <= '9') {
+        return (ch - '0');
+    } else if (ch >= 'a' && ch <= 'f') {
+        return 10 + (ch - 'a');
+    } else if (ch >= 'A' && ch <= 'F') {
+        return 10 + (ch - 'A');
+    }
+
+    return -1;
+}
+
+/* Compare the binary fingerprint (hash of host key) with the
+ * host_key_check parameter.
+ */
+static int compare_fingerprint(const unsigned char *fingerprint, size_t len,
+                               const char *host_key_check)
+{
+    unsigned c;
+
+    while (len > 0) {
+        while (*host_key_check == ':')
+            host_key_check++;
+        if (!qemu_isxdigit(host_key_check[0]) ||
+            !qemu_isxdigit(host_key_check[1]))
+            return 1;
+        c = hex2decimal(host_key_check[0]) * 16 +
+            hex2decimal(host_key_check[1]);
+        if (c - *fingerprint != 0)
+            return c - *fingerprint;
+        fingerprint++;
+        len--;
+        host_key_check += 2;
+    }
+    return *host_key_check - '\0';
+}
+
+static int
+check_host_key_hash(BDRVSSHState *s, const char *hash,
+                    int hash_type, size_t fingerprint_len)
+{
+    const char *fingerprint;
+
+    fingerprint = libssh2_hostkey_hash(s->session, hash_type);
+    if (!fingerprint) {
+        session_error_report(s, "failed to read remote host key");
+        return -EINVAL;
+    }
+
+    if(compare_fingerprint((unsigned char *) fingerprint, fingerprint_len,
+                           hash) != 0) {
+        error_report("remote host key does not match host_key_check '%s'",
+                     hash);
+        return -EPERM;
+    }
+
+    return 0;
+}
+
+static int check_host_key(BDRVSSHState *s, const char *host, int port,
+                          const char *host_key_check)
+{
+    /* host_key_check=no */
+    if (strcmp(host_key_check, "no") == 0) {
+        return 0;
+    }
+
+    /* host_key_check=md5:xx:yy:zz:... */
+    if (strlen(host_key_check) >= 4 &&
+        strncmp(host_key_check, "md5:", 4) == 0) {
+        return check_host_key_hash(s, &host_key_check[4],
+                                   LIBSSH2_HOSTKEY_HASH_MD5, 16);
+    }
+
+    /* host_key_check=sha1:xx:yy:zz:... */
+    if (strlen(host_key_check) >= 5 &&
+        strncmp(host_key_check, "sha1:", 5) == 0) {
+        return check_host_key_hash(s, &host_key_check[5],
+                                   LIBSSH2_HOSTKEY_HASH_SHA1, 20);
+    }
+
+    /* host_key_check=yes */
+    if (strcmp(host_key_check, "yes") == 0) {
+        return check_host_key_knownhosts(s, host, port);
+    }
+
+    error_report("unknown host_key_check setting (%s)", host_key_check);
+    return -EINVAL;
+}
+
+static int authenticate(BDRVSSHState *s, const char *user)
+{
+    int r, ret;
+    const char *userauthlist;
+    LIBSSH2_AGENT *agent = NULL;
+    struct libssh2_agent_publickey *identity;
+    struct libssh2_agent_publickey *prev_identity = NULL;
+
+    userauthlist = libssh2_userauth_list(s->session, user, strlen(user));
+    if (strstr(userauthlist, "publickey") == NULL) {
+        ret = -EPERM;
+        error_report("remote server does not support \"publickey\" authentication");
+        goto out;
+    }
+
+    /* Connect to ssh-agent and try each identity in turn. */
+    agent = libssh2_agent_init(s->session);
+    if (!agent) {
+        ret = -EINVAL;
+        session_error_report(s, "failed to initialize ssh-agent support");
+        goto out;
+    }
+    if (libssh2_agent_connect(agent)) {
+        ret = -ECONNREFUSED;
+        session_error_report(s, "failed to connect to ssh-agent");
+        goto out;
+    }
+    if (libssh2_agent_list_identities(agent)) {
+        ret = -EINVAL;
+        session_error_report(s, "failed requesting identities from ssh-agent");
+        goto out;
+    }
+
+    for(;;) {
+        r = libssh2_agent_get_identity(agent, &identity, prev_identity);
+        if (r == 1) {           /* end of list */
+            break;
+        }
+        if (r < 0) {
+            ret = -EINVAL;
+            session_error_report(s, "failed to obtain identity from ssh-agent");
+            goto out;
+        }
+        r = libssh2_agent_userauth(agent, user, identity);
+        if (r == 0) {
+            /* Authenticated! */
+            ret = 0;
+            goto out;
+        }
+        /* Failed to authenticate with this identity, try the next one. */
+        prev_identity = identity;
+    }
+
+    ret = -EPERM;
+    error_report("failed to authenticate using publickey authentication "
+                 "and the identities held by your ssh-agent");
+
+ out:
+    if (agent != NULL) {
+        /* Note: libssh2 implementation implicitly calls
+         * libssh2_agent_disconnect if necessary.
+         */
+        libssh2_agent_free(agent);
+    }
+
+    return ret;
+}
+
+static int connect_to_ssh(BDRVSSHState *s, QDict *options,
+                          int ssh_flags, int creat_mode)
+{
+    int r, ret;
+    Error *err = NULL;
+    const char *host, *user, *path, *host_key_check;
+    int port;
+
+    host = qdict_get_str(options, "host");
+
+    if (qdict_haskey(options, "port")) {
+        port = qdict_get_int(options, "port");
+    } else {
+        port = 22;
+    }
+
+    path = qdict_get_str(options, "path");
+
+    if (qdict_haskey(options, "user")) {
+        user = qdict_get_str(options, "user");
+    } else {
+        user = g_get_user_name();
+        if (!user) {
+            ret = -errno;
+            goto err;
+        }
+    }
+
+    if (qdict_haskey(options, "host_key_check")) {
+        host_key_check = qdict_get_str(options, "host_key_check");
+    } else {
+        host_key_check = "yes";
+    }
+
+    /* Construct the host:port name for inet_connect. */
+    g_free(s->hostport);
+    s->hostport = g_strdup_printf("%s:%d", host, port);
+
+    /* Open the socket and connect. */
+    s->sock = inet_connect(s->hostport, &err);
+    if (err != NULL) {
+        ret = -errno;
+        qerror_report_err(err);
+        error_free(err);
+        goto err;
+    }
+
+    /* Create SSH session. */
+    s->session = libssh2_session_init();
+    if (!s->session) {
+        ret = -EINVAL;
+        session_error_report(s, "failed to initialize libssh2 session");
+        goto err;
+    }
+
+#if TRACE_LIBSSH2 != 0
+    libssh2_trace(s->session, TRACE_LIBSSH2);
+#endif
+
+    r = libssh2_session_handshake(s->session, s->sock);
+    if (r != 0) {
+        ret = -EINVAL;
+        session_error_report(s, "failed to establish SSH session");
+        goto err;
+    }
+
+    /* Check the remote host's key against known_hosts. */
+    ret = check_host_key(s, host, port, host_key_check);
+    if (ret < 0) {
+        goto err;
+    }
+
+    /* Authenticate. */
+    ret = authenticate(s, user);
+    if (ret < 0) {
+        goto err;
+    }
+
+    /* Start SFTP. */
+    s->sftp = libssh2_sftp_init(s->session);
+    if (!s->sftp) {
+        session_error_report(s, "failed to initialize sftp handle");
+        ret = -EINVAL;
+        goto err;
+    }
+
+    /* Open the remote file. */
+    DPRINTF("opening file %s flags=0x%x creat_mode=0%o",
+            path, ssh_flags, creat_mode);
+    s->sftp_handle = libssh2_sftp_open(s->sftp, path, ssh_flags, creat_mode);
+    if (!s->sftp_handle) {
+        session_error_report(s, "failed to open remote file '%s'", path);
+        ret = -EINVAL;
+        goto err;
+    }
+
+    r = libssh2_sftp_fstat(s->sftp_handle, &s->attrs);
+    if (r < 0) {
+        sftp_error_report(s, "failed to read file attributes");
+        return -EINVAL;
+    }
+
+    /* Delete the options we've used; any not deleted will cause the
+     * block layer to give an error about unused options.
+     */
+    qdict_del(options, "host");
+    qdict_del(options, "port");
+    qdict_del(options, "user");
+    qdict_del(options, "path");
+    qdict_del(options, "host_key_check");
+
+    return 0;
+
+ err:
+    if (s->sftp_handle) {
+        libssh2_sftp_close(s->sftp_handle);
+    }
+    s->sftp_handle = NULL;
+    if (s->sftp) {
+        libssh2_sftp_shutdown(s->sftp);
+    }
+    s->sftp = NULL;
+    if (s->session) {
+        libssh2_session_disconnect(s->session,
+                                   "from qemu ssh client: "
+                                   "error opening connection");
+        libssh2_session_free(s->session);
+    }
+    s->session = NULL;
+
+    return ret;
+}
+
+static int ssh_file_open(BlockDriverState *bs, const char *filename,
+                         QDict *options, int bdrv_flags)
+{
+    BDRVSSHState *s = bs->opaque;
+    int ret;
+    int ssh_flags;
+
+    ssh_state_init(s);
+
+    ssh_flags = LIBSSH2_FXF_READ;
+    if (bdrv_flags & BDRV_O_RDWR) {
+        ssh_flags |= LIBSSH2_FXF_WRITE;
+    }
+
+    /* Start up SSH. */
+    ret = connect_to_ssh(s, options, ssh_flags, 0);
+    if (ret < 0) {
+        goto err;
+    }
+
+    /* Go non-blocking. */
+    libssh2_session_set_blocking(s->session, 0);
+
+    return 0;
+
+ err:
+    if (s->sock >= 0) {
+        close(s->sock);
+    }
+    s->sock = -1;
+
+    return ret;
+}
+
+static QEMUOptionParameter ssh_create_options[] = {
+    {
+        .name = BLOCK_OPT_SIZE,
+        .type = OPT_SIZE,
+        .help = "Virtual disk size"
+    },
+    { NULL }
+};
+
+static int ssh_create(const char *filename, QEMUOptionParameter *options)
+{
+    int r, ret;
+    Error *local_err = NULL;
+    int64_t total_size = 0;
+    QDict *uri_options = NULL;
+    BDRVSSHState s;
+    ssize_t r2;
+    char c[1] = { '\0' };
+
+    ssh_state_init(&s);
+
+    /* Get desired file size. */
+    while (options && options->name) {
+        if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
+            total_size = options->value.n;
+        }
+        options++;
+    }
+    DPRINTF("total_size=%" PRIi64, total_size);
+
+    uri_options = qdict_new();
+    r = parse_uri(filename, uri_options, &local_err);
+    if (r < 0) {
+        qerror_report_err(local_err);
+        error_free(local_err);
+        ret = r;
+        goto out;
+    }
+
+    r = connect_to_ssh(&s, uri_options,
+                       LIBSSH2_FXF_READ|LIBSSH2_FXF_WRITE|
+                       LIBSSH2_FXF_CREAT|LIBSSH2_FXF_TRUNC, 0644);
+    if (r < 0) {
+        ret = r;
+        goto out;
+    }
+
+    if (total_size > 0) {
+        libssh2_sftp_seek64(s.sftp_handle, total_size-1);
+        r2 = libssh2_sftp_write(s.sftp_handle, c, 1);
+        if (r2 < 0) {
+            sftp_error_report(&s, "truncate failed");
+            ret = -EINVAL;
+            goto out;
+        }
+        s.attrs.filesize = total_size;
+    }
+
+    ret = 0;
+
+ out:
+    ssh_state_free(&s);
+    if (uri_options != NULL) {
+        QDECREF(uri_options);
+    }
+    return ret;
+}
+
+static void ssh_close(BlockDriverState *bs)
+{
+    BDRVSSHState *s = bs->opaque;
+
+    ssh_state_free(s);
+}
+
+static void restart_coroutine(void *opaque)
+{
+    Coroutine *co = opaque;
+
+    DPRINTF("co=%p", co);
+
+    qemu_coroutine_enter(co, NULL);
+}
+
+/* Always true because when we have called set_fd_handler there is
+ * always a request being processed.
+ */
+static int return_true(void *opaque)
+{
+    return 1;
+}
+
+static coroutine_fn void set_fd_handler(BDRVSSHState *s)
+{
+    int r;
+    IOHandler *rd_handler = NULL, *wr_handler = NULL;
+    Coroutine *co = qemu_coroutine_self();
+
+    r = libssh2_session_block_directions(s->session);
+
+    if (r & LIBSSH2_SESSION_BLOCK_INBOUND) {
+        rd_handler = restart_coroutine;
+    }
+    if (r & LIBSSH2_SESSION_BLOCK_OUTBOUND) {
+        wr_handler = restart_coroutine;
+    }
+
+    DPRINTF("s->sock=%d rd_handler=%p wr_handler=%p", s->sock,
+            rd_handler, wr_handler);
+
+    qemu_aio_set_fd_handler(s->sock, rd_handler, wr_handler, return_true, co);
+}
+
+static coroutine_fn void clear_fd_handler(BDRVSSHState *s)
+{
+    DPRINTF("s->sock=%d", s->sock);
+    qemu_aio_set_fd_handler(s->sock, NULL, NULL, NULL, NULL);
+}
+
+/* A non-blocking call returned EAGAIN, so yield, ensuring the
+ * handlers are set up so that we'll be rescheduled when there is an
+ * interesting event on the socket.
+ */
+static coroutine_fn void co_yield(BDRVSSHState *s)
+{
+    set_fd_handler(s);
+    qemu_coroutine_yield();
+    clear_fd_handler(s);
+}
+
+/* SFTP has a function `libssh2_sftp_seek64' which seeks to a position
+ * in the remote file.  Notice that it just updates a field in the
+ * sftp_handle structure, so there is no network traffic and it cannot
+ * fail.
+ *
+ * However, `libssh2_sftp_seek64' does have a catastrophic effect on
+ * performance since it causes the handle to throw away all in-flight
+ * reads and buffered readahead data.  Therefore this function tries
+ * to be intelligent about when to call the underlying libssh2 function.
+ */
+#define SSH_SEEK_WRITE 0
+#define SSH_SEEK_READ  1
+#define SSH_SEEK_FORCE 2
+
+static void ssh_seek(BDRVSSHState *s, int64_t offset, int flags)
+{
+    bool op_read = (flags & SSH_SEEK_READ) != 0;
+    bool force = (flags & SSH_SEEK_FORCE) != 0;
+
+    if (force || op_read != s->offset_op_read || offset != s->offset) {
+        DPRINTF("seeking to offset=%" PRIi64, offset);
+        libssh2_sftp_seek64(s->sftp_handle, offset);
+        s->offset = offset;
+        s->offset_op_read = op_read;
+    }
+}
+
+static coroutine_fn int ssh_read(BDRVSSHState *s,
+                                 int64_t offset, size_t size,
+                                 QEMUIOVector *qiov)
+{
+    ssize_t r;
+    size_t got;
+    char *buf, *end_of_vec;
+    struct iovec *i;
+
+    DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
+
+    ssh_seek(s, offset, SSH_SEEK_READ);
+
+    /* This keeps track of the current iovec element ('i'), where we
+     * will write to next ('buf'), and the end of the current iovec
+     * ('end_of_vec').
+     */
+    i = &qiov->iov[0];
+    buf = i->iov_base;
+    end_of_vec = i->iov_base + i->iov_len;
+
+    /* libssh2 has a hard-coded limit of 2000 bytes per request,
+     * although it will also do readahead behind our backs.  Therefore
+     * we may have to do repeated reads here until we have read 'size'
+     * bytes.
+     */
+    for (got = 0; got < size; ) {
+    again:
+        DPRINTF("sftp_read buf=%p size=%zu", buf, end_of_vec - buf);
+        r = libssh2_sftp_read(s->sftp_handle, buf, end_of_vec - buf);
+        DPRINTF("sftp_read returned %zd", r);
+
+        if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
+            co_yield(s);
+            goto again;
+        }
+        if (r < 0) {
+            sftp_error_report(s, "read failed");
+            s->offset = -1;
+            return -EIO;
+        }
+        if (r == 0) {
+            /* EOF: Short read so pad the buffer with zeroes and return it. */
+            qemu_iovec_memset(qiov, got, 0, size - got);
+            return 0;
+        }
+
+        got += r;
+        buf += r;
+        s->offset += r;
+        if (buf >= end_of_vec && got < size) {
+            i++;
+            buf = i->iov_base;
+            end_of_vec = i->iov_base + i->iov_len;
+        }
+    }
+
+    return 0;
+}
+
+static coroutine_fn int ssh_co_readv(BlockDriverState *bs,
+                                     int64_t sector_num,
+                                     int nb_sectors, QEMUIOVector *qiov)
+{
+    BDRVSSHState *s = bs->opaque;
+    int ret;
+
+    qemu_co_mutex_lock(&s->lock);
+    ret = ssh_read(s, sector_num * BDRV_SECTOR_SIZE,
+                   nb_sectors * BDRV_SECTOR_SIZE, qiov);
+    qemu_co_mutex_unlock(&s->lock);
+
+    return ret;
+}
+
+static int ssh_write(BDRVSSHState *s,
+                     int64_t offset, size_t size,
+                     QEMUIOVector *qiov)
+{
+    ssize_t r;
+    size_t written;
+    char *buf, *end_of_vec;
+    struct iovec *i;
+
+    DPRINTF("offset=%" PRIi64 " size=%zu", offset, size);
+
+    ssh_seek(s, offset, SSH_SEEK_WRITE);
+
+    /* This keeps track of the current iovec element ('i'), where we
+     * will read from next ('buf'), and the end of the current iovec
+     * ('end_of_vec').
+     */
+    i = &qiov->iov[0];
+    buf = i->iov_base;
+    end_of_vec = i->iov_base + i->iov_len;
+
+    for (written = 0; written < size; ) {
+    again:
+        DPRINTF("sftp_write buf=%p size=%zu", buf, end_of_vec - buf);
+        r = libssh2_sftp_write(s->sftp_handle, buf, end_of_vec - buf);
+        DPRINTF("sftp_write returned %zd", r);
+
+        if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
+            co_yield(s);
+            goto again;
+        }
+        if (r < 0) {
+            sftp_error_report(s, "write failed");
+            s->offset = -1;
+            return -EIO;
+        }
+        /* The libssh2 API is very unclear about this.  A comment in
+         * the code says "nothing was acked, and no EAGAIN was
+         * received!" which apparently means that no data got sent
+         * out, and the underlying channel didn't return any EAGAIN
+         * indication.  I think this is a bug in either libssh2 or
+         * OpenSSH (server-side).  In any case, forcing a seek (to
+         * discard libssh2 internal buffers), and then trying again
+         * works for me.
+         */
+        if (r == 0) {
+            ssh_seek(s, offset + written, SSH_SEEK_WRITE|SSH_SEEK_FORCE);
+            co_yield(s);
+            goto again;
+        }
+
+        written += r;
+        buf += r;
+        s->offset += r;
+        if (buf >= end_of_vec && written < size) {
+            i++;
+            buf = i->iov_base;
+            end_of_vec = i->iov_base + i->iov_len;
+        }
+
+        if (offset + written > s->attrs.filesize)
+            s->attrs.filesize = offset + written;
+    }
+
+    return 0;
+}
+
+static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
+                                      int64_t sector_num,
+                                      int nb_sectors, QEMUIOVector *qiov)
+{
+    BDRVSSHState *s = bs->opaque;
+    int ret;
+
+    qemu_co_mutex_lock(&s->lock);
+    ret = ssh_write(s, sector_num * BDRV_SECTOR_SIZE,
+                    nb_sectors * BDRV_SECTOR_SIZE, qiov);
+    qemu_co_mutex_unlock(&s->lock);
+
+    return ret;
+}
+
+static void unsafe_flush_warning(BDRVSSHState *s, const char *what)
+{
+    if (!s->unsafe_flush_warning) {
+        error_report("warning: ssh server %s does not support fsync",
+                     s->hostport);
+        if (what) {
+            error_report("to support fsync, you need %s", what);
+        }
+        s->unsafe_flush_warning = true;
+    }
+}
+
+#ifdef HAS_LIBSSH2_SFTP_FSYNC
+
+static coroutine_fn int ssh_flush(BDRVSSHState *s)
+{
+    int r;
+
+    DPRINTF("fsync");
+ again:
+    r = libssh2_sftp_fsync(s->sftp_handle);
+    if (r == LIBSSH2_ERROR_EAGAIN || r == LIBSSH2_ERROR_TIMEOUT) {
+        co_yield(s);
+        goto again;
+    }
+    if (r == LIBSSH2_ERROR_SFTP_PROTOCOL &&
+        libssh2_sftp_last_error(s->sftp) == LIBSSH2_FX_OP_UNSUPPORTED) {
+        unsafe_flush_warning(s, "OpenSSH >= 6.3");
+        return 0;
+    }
+    if (r < 0) {
+        sftp_error_report(s, "fsync failed");
+        return -EIO;
+    }
+
+    return 0;
+}
+
+static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
+{
+    BDRVSSHState *s = bs->opaque;
+    int ret;
+
+    qemu_co_mutex_lock(&s->lock);
+    ret = ssh_flush(s);
+    qemu_co_mutex_unlock(&s->lock);
+
+    return ret;
+}
+
+#else /* !HAS_LIBSSH2_SFTP_FSYNC */
+
+static coroutine_fn int ssh_co_flush(BlockDriverState *bs)
+{
+    BDRVSSHState *s = bs->opaque;
+
+    unsafe_flush_warning(s, "libssh2 >= 1.4.4");
+    return 0;
+}
+
+#endif /* !HAS_LIBSSH2_SFTP_FSYNC */
+
+static int64_t ssh_getlength(BlockDriverState *bs)
+{
+    BDRVSSHState *s = bs->opaque;
+    int64_t length;
+
+    /* Note we cannot make a libssh2 call here. */
+    length = (int64_t) s->attrs.filesize;
+    DPRINTF("length=%" PRIi64, length);
+
+    return length;
+}
+
+static BlockDriver bdrv_ssh = {
+    .format_name                  = "ssh",
+    .protocol_name                = "ssh",
+    .instance_size                = sizeof(BDRVSSHState),
+    .bdrv_parse_filename          = ssh_parse_filename,
+    .bdrv_file_open               = ssh_file_open,
+    .bdrv_create                  = ssh_create,
+    .bdrv_close                   = ssh_close,
+    .bdrv_co_readv                = ssh_co_readv,
+    .bdrv_co_writev               = ssh_co_writev,
+    .bdrv_getlength               = ssh_getlength,
+    .bdrv_co_flush_to_disk        = ssh_co_flush,
+    .create_options               = ssh_create_options,
+};
+
+static void bdrv_ssh_init(void)
+{
+    int r;
+
+    r = libssh2_init(0);
+    if (r != 0) {
+        fprintf(stderr, "libssh2 initialization failed, %d\n", r);
+        exit(EXIT_FAILURE);
+    }
+
+    bdrv_register(&bdrv_ssh);
+}
+
+block_init(bdrv_ssh_init);
diff --git a/configure b/configure
index 73df181406..a97bf311d3 100755
--- a/configure
+++ b/configure
@@ -239,6 +239,7 @@ virtio_blk_data_plane=""
 gtk=""
 gtkabi="2.0"
 tpm="no"
+libssh2=""
 
 # parse CC options first
 for opt do
@@ -922,6 +923,10 @@ for opt do
   ;;
   --enable-tpm) tpm="yes"
   ;;
+  --disable-libssh2) libssh2="no"
+  ;;
+  --enable-libssh2) libssh2="yes"
+  ;;
   *) echo "ERROR: unknown option $opt"; show_help="yes"
   ;;
   esac
@@ -1182,6 +1187,8 @@ echo "  --disable-glusterfs      disable GlusterFS backend"
 echo "  --enable-gcov            enable test coverage analysis with gcov"
 echo "  --gcov=GCOV              use specified gcov [$gcov_tool]"
 echo "  --enable-tpm             enable TPM support"
+echo "  --disable-libssh2        disable ssh block device support"
+echo "  --enable-libssh2         enable ssh block device support"
 echo ""
 echo "NOTE: The object files are built at the place where configure is launched"
 exit 1
@@ -2314,6 +2321,67 @@ EOF
 fi
 
 ##########################################
+# libssh2 probe
+if test "$libssh2" != "no" ; then
+  cat > $TMPC <<EOF
+#include <stdio.h>
+#include <libssh2.h>
+#include <libssh2_sftp.h>
+int main(void) {
+    LIBSSH2_SESSION *session;
+    session = libssh2_session_init ();
+    (void) libssh2_sftp_init (session);
+    return 0;
+}
+EOF
+
+  if $pkg_config libssh2 --modversion >/dev/null 2>&1; then
+    libssh2_cflags=`$pkg_config libssh2 --cflags`
+    libssh2_libs=`$pkg_config libssh2 --libs`
+  else
+    libssh2_cflags=
+    libssh2_libs="-lssh2"
+  fi
+
+  if compile_prog "$libssh2_cflags" "$libssh2_libs" ; then
+    libssh2=yes
+    libs_tools="$libssh2_libs $libs_tools"
+    libs_softmmu="$libssh2_libs $libs_softmmu"
+    QEMU_CFLAGS="$QEMU_CFLAGS $libssh2_cflags"
+  else
+    if test "$libssh2" = "yes" ; then
+      feature_not_found "libssh2"
+    fi
+    libssh2=no
+  fi
+fi
+
+##########################################
+# libssh2_sftp_fsync probe
+
+if test "$libssh2" = "yes"; then
+  cat > $TMPC <<EOF
+#include <stdio.h>
+#include <libssh2.h>
+#include <libssh2_sftp.h>
+int main(void) {
+    LIBSSH2_SESSION *session;
+    LIBSSH2_SFTP *sftp;
+    LIBSSH2_SFTP_HANDLE *sftp_handle;
+    session = libssh2_session_init ();
+    sftp = libssh2_sftp_init (session);
+    sftp_handle = libssh2_sftp_open (sftp, "/", 0, 0);
+    libssh2_sftp_fsync (sftp_handle);
+    return 0;
+}
+EOF
+  # libssh2_cflags/libssh2_libs defined in previous test.
+  if compile_prog "$libssh2_cflags" "$libssh2_libs" ; then
+    QEMU_CFLAGS="-DHAS_LIBSSH2_SFTP_FSYNC $QEMU_CFLAGS"
+  fi
+fi
+
+##########################################
 # linux-aio probe
 
 if test "$linux_aio" != "no" ; then
@@ -3435,6 +3503,7 @@ echo "virtio-blk-data-plane $virtio_blk_data_plane"
 echo "gcov              $gcov_tool"
 echo "gcov enabled      $gcov"
 echo "TPM support       $tpm"
+echo "libssh2 support   $libssh2"
 
 if test "$sdl_too_old" = "yes"; then
 echo "-> Your SDL version is too old - please upgrade to have SDL support"
@@ -3793,6 +3862,10 @@ if test "$glusterfs" = "yes" ; then
   echo "CONFIG_GLUSTERFS=y" >> $config_host_mak
 fi
 
+if test "$libssh2" = "yes" ; then
+  echo "CONFIG_LIBSSH2=y" >> $config_host_mak
+fi
+
 if test "$virtio_blk_data_plane" = "yes" ; then
   echo 'CONFIG_VIRTIO_BLK_DATA_PLANE=$(CONFIG_VIRTIO)' >> $config_host_mak
 fi
diff --git a/hw/ide/core.c b/hw/ide/core.c
index 87d67b7bcb..c7a80413be 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -1262,6 +1262,10 @@ void ide_exec_cmd(IDEBus *bus, uint32_t val)
         lba48 = 1;
         /* fall through */
     case WIN_READ_NATIVE_MAX:
+        /* Refuse if no sectors are addressable (e.g. medium not inserted) */
+        if (s->nb_sectors == 0) {
+            goto abort_cmd;
+        }
 	ide_cmd_lba48_transform(s, lba48);
         ide_set_sector(s, s->nb_sectors - 1);
         s->status = READY_STAT | SEEK_STAT;
diff --git a/include/block/block.h b/include/block/block.h
index 9dc6aada99..ebd95127a1 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -166,10 +166,12 @@ int bdrv_read_unthrottled(BlockDriverState *bs, int64_t sector_num,
                           uint8_t *buf, int nb_sectors);
 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
                const uint8_t *buf, int nb_sectors);
+int bdrv_writev(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov);
 int bdrv_pread(BlockDriverState *bs, int64_t offset,
                void *buf, int count);
 int bdrv_pwrite(BlockDriverState *bs, int64_t offset,
                 const void *buf, int count);
+int bdrv_pwritev(BlockDriverState *bs, int64_t offset, QEMUIOVector *qiov);
 int bdrv_pwrite_sync(BlockDriverState *bs, int64_t offset,
     const void *buf, int count);
 int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
@@ -348,6 +350,7 @@ void path_combine(char *dest, int dest_size,
                   const char *base_path,
                   const char *filename);
 
+int bdrv_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
 int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
                       int64_t pos, int size);
 
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 9aa98b5d12..458cde3766 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -164,8 +164,8 @@ struct BlockDriver {
                                   const char *snapshot_name);
     int (*bdrv_get_info)(BlockDriverState *bs, BlockDriverInfo *bdi);
 
-    int (*bdrv_save_vmstate)(BlockDriverState *bs, const uint8_t *buf,
-                             int64_t pos, int size);
+    int (*bdrv_save_vmstate)(BlockDriverState *bs, QEMUIOVector *qiov,
+                             int64_t pos);
     int (*bdrv_load_vmstate)(BlockDriverState *bs, uint8_t *buf,
                              int64_t pos, int size);
 
diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 623c434b15..7519464192 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -55,7 +55,7 @@ typedef int (QEMUFileGetFD)(void *opaque);
  * This function writes an iovec to file.
  */
 typedef ssize_t (QEMUFileWritevBufferFunc)(void *opaque, struct iovec *iov,
-                                           int iovcnt);
+                                           int iovcnt, int64_t pos);
 
 typedef struct QEMUFileOps {
     QEMUFilePutBufferFunc *put_buffer;
diff --git a/qemu-doc.texi b/qemu-doc.texi
index af84bef0e9..dfea4d3799 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -423,6 +423,7 @@ snapshots.
 * disk_images_sheepdog::      Sheepdog disk images
 * disk_images_iscsi::         iSCSI LUNs
 * disk_images_gluster::       GlusterFS disk images
+* disk_images_ssh::           Secure Shell (ssh) disk images
 @end menu
 
 @node disk_images_quickstart
@@ -1038,6 +1039,59 @@ qemu-system-x86_64 -drive file=gluster+unix:///testvol/dir/a.img?socket=/tmp/glu
 qemu-system-x86_64 -drive file=gluster+rdma://1.2.3.4:24007/testvol/a.img
 @end example
 
+@node disk_images_ssh
+@subsection Secure Shell (ssh) disk images
+
+You can access disk images located on a remote ssh server
+by using the ssh protocol:
+
+@example
+qemu-system-x86_64 -drive file=ssh://[@var{user}@@]@var{server}[:@var{port}]/@var{path}[?host_key_check=@var{host_key_check}]
+@end example
+
+Alternative syntax using properties:
+
+@example
+qemu-system-x86_64 -drive file.driver=ssh[,file.user=@var{user}],file.host=@var{server}[,file.port=@var{port}],file.path=@var{path}[,file.host_key_check=@var{host_key_check}]
+@end example
+
+@var{ssh} is the protocol.
+
+@var{user} is the remote user.  If not specified, then the local
+username is tried.
+
+@var{server} specifies the remote ssh server.  Any ssh server can be
+used, but it must implement the sftp-server protocol.  Most Unix/Linux
+systems should work without requiring any extra configuration.
+
+@var{port} is the port number on which sshd is listening.  By default
+the standard ssh port (22) is used.
+
+@var{path} is the path to the disk image.
+
+The optional @var{host_key_check} parameter controls how the remote
+host's key is checked.  The default is @code{yes} which means to use
+the local @file{.ssh/known_hosts} file.  Setting this to @code{no}
+turns off known-hosts checking.  Or you can check that the host key
+matches a specific fingerprint:
+@code{host_key_check=md5:78:45:8e:14:57:4f:d5:45:83:0a:0e:f3:49:82:c9:c8}
+(@code{sha1:} can also be used as a prefix, but note that OpenSSH
+tools only use MD5 to print fingerprints).
+
+Currently authentication must be done using ssh-agent.  Other
+authentication methods may be supported in future.
+
+Note: Many ssh servers do not support an @code{fsync}-style operation.
+The ssh driver cannot guarantee that disk flush requests are
+obeyed, and this causes a risk of disk corruption if the remote
+server or network goes down during writes.  The driver will
+print a warning when @code{fsync} is not supported:
+
+warning: ssh server @code{ssh.example.com:22} does not support fsync
+
+With sufficiently new versions of libssh2 and OpenSSH, @code{fsync} is
+supported.
+
 @node pcsys_network
 @section Network emulation
 
diff --git a/qemu-options.hx b/qemu-options.hx
index 7cd6002d95..5c115d1cf9 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -2107,6 +2107,18 @@ Example for Unix Domain Sockets
 qemu-system-i386 --drive file=nbd:unix:/tmp/nbd-socket
 @end example
 
+@item SSH
+QEMU supports SSH (Secure Shell) access to remote disks.
+
+Examples:
+@example
+qemu-system-i386 -drive file=ssh://user@@host/path/to/disk.img
+qemu-system-i386 -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
+@end example
+
+Currently authentication must be done using ssh-agent.  Other
+authentication methods may be supported in future.
+
 @item Sheepdog
 Sheepdog is a distributed storage system for QEMU.
 QEMU supports using either local sheepdog devices or remote networked
diff --git a/savevm.c b/savevm.c
index 63f4c828a9..53515cb794 100644
--- a/savevm.c
+++ b/savevm.c
@@ -175,7 +175,8 @@ static void coroutine_fn yield_until_fd_readable(int fd)
     qemu_coroutine_yield();
 }
 
-static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt)
+static ssize_t socket_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
+                                    int64_t pos)
 {
     QEMUFileSocket *s = opaque;
     ssize_t len;
@@ -457,6 +458,21 @@ fail:
     return NULL;
 }
 
+static ssize_t block_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
+                                   int64_t pos)
+{
+    int ret;
+    QEMUIOVector qiov;
+
+    qemu_iovec_init_external(&qiov, iov, iovcnt);
+    ret = bdrv_writev_vmstate(opaque, &qiov, pos);
+    if (ret < 0) {
+        return ret;
+    }
+
+    return qiov.size;
+}
+
 static int block_put_buffer(void *opaque, const uint8_t *buf,
                            int64_t pos, int size)
 {
@@ -480,8 +496,9 @@ static const QEMUFileOps bdrv_read_ops = {
 };
 
 static const QEMUFileOps bdrv_write_ops = {
-    .put_buffer = block_put_buffer,
-    .close =      bdrv_fclose
+    .put_buffer     = block_put_buffer,
+    .writev_buffer  = block_writev_buffer,
+    .close          = bdrv_fclose
 };
 
 static QEMUFile *qemu_fopen_bdrv(BlockDriverState *bs, int is_writable)
@@ -535,7 +552,7 @@ static void qemu_fflush(QEMUFile *f)
 
     if (f->ops->writev_buffer) {
         if (f->iovcnt > 0) {
-            ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt);
+            ret = f->ops->writev_buffer(f->opaque, f->iov, f->iovcnt, f->pos);
         }
     } else {
         if (f->buf_index > 0) {
diff --git a/tests/qemu-iotests/002 b/tests/qemu-iotests/002
index bebed84fd9..51d0a8f4ad 100755
--- a/tests/qemu-iotests/002
+++ b/tests/qemu-iotests/002
@@ -61,10 +61,23 @@ $QEMU_IO -c "read -pP 0xa 0 $size" $TEST_IMG | _filter_qemu_io
 echo
 echo "unaligned pwrite"
 $QEMU_IO -c 'write -pP 0xab 66 42' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'write -pP 0xac 512 288' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'write -pP 0xad 800 224' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'write -pP 0xae 66000 128k' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'write -pP 0xaf 256k 42' $TEST_IMG | _filter_qemu_io
 
 echo
 echo "verify pattern"
+$QEMU_IO -c 'read -pP 0xa 0 66' $TEST_IMG | _filter_qemu_io
 $QEMU_IO -c 'read -pP 0xab 66 42' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xa 108 404' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xac 512 288' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xad 800 224' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xa 1k 64976' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xae 66000 128k' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xa 197072 65072' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xaf 256k 42' $TEST_IMG | _filter_qemu_io
+$QEMU_IO -c 'read -pP 0xa 262186 470' $TEST_IMG | _filter_qemu_io
 
 # success, all done
 echo "*** done"
diff --git a/tests/qemu-iotests/002.out b/tests/qemu-iotests/002.out
index 75f5876e88..cd6aa0f9fa 100644
--- a/tests/qemu-iotests/002.out
+++ b/tests/qemu-iotests/002.out
@@ -16,8 +16,34 @@ read 134217728/134217728 bytes at offset 0
 unaligned pwrite
 wrote 42/42 bytes at offset 66
 42 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 288/288 bytes at offset 512
+288 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 224/224 bytes at offset 800
+224 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 131072/131072 bytes at offset 66000
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 42/42 bytes at offset 262144
+42 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 
 verify pattern
+read 66/66 bytes at offset 0
+66 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 42/42 bytes at offset 66
 42 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 404/404 bytes at offset 108
+404 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 288/288 bytes at offset 512
+288 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 224/224 bytes at offset 800
+224 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 64976/64976 bytes at offset 1024
+63.453 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 131072/131072 bytes at offset 66000
+128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 65072/65072 bytes at offset 197072
+63.547 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 42/42 bytes at offset 262144
+42 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 470/470 bytes at offset 262186
+470 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 *** done
diff --git a/tests/qemu-iotests/051 b/tests/qemu-iotests/051
new file mode 100755
index 0000000000..8b51de3f31
--- /dev/null
+++ b/tests/qemu-iotests/051
@@ -0,0 +1,148 @@
+#!/bin/bash
+#
+# Test command line configuration of block devices and driver-specific options
+#
+# Copyright (C) 2013 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=kwolf@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt qcow2
+_supported_proto file
+_supported_os Linux
+
+function do_run_qemu()
+{
+    echo Testing: "$@"
+    echo quit | $QEMU -nographic -monitor stdio -serial none "$@"
+    echo
+}
+
+function run_qemu()
+{
+    do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qemu
+}
+
+size=128M
+
+_make_test_img $size
+
+echo
+echo === Unknown option ===
+echo
+
+run_qemu -drive file=$TEST_IMG,format=qcow2,unknown_opt=
+run_qemu -drive file=$TEST_IMG,format=qcow2,unknown_opt=on
+run_qemu -drive file=$TEST_IMG,format=qcow2,unknown_opt=1234
+run_qemu -drive file=$TEST_IMG,format=qcow2,unknown_opt=foo
+
+
+echo
+echo === Enable and disable lazy refcounting on the command line, plus some invalid values ===
+echo
+
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=on
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=off
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=42
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=foo
+
+
+echo
+echo === With version 2 images enabling lazy refcounts must fail ===
+echo
+
+_make_test_img -ocompat=0.10 $size
+
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=on
+run_qemu -drive file=$TEST_IMG,format=qcow2,lazy_refcounts=off
+
+echo
+echo === No medium ===
+echo
+
+run_qemu -drive if=floppy
+run_qemu -drive if=ide,media=cdrom
+run_qemu -drive if=scsi,media=cdrom
+
+run_qemu -drive if=ide
+run_qemu -drive if=virtio
+run_qemu -drive if=scsi
+
+run_qemu -drive if=none,id=disk -device ide-cd,drive=disk
+run_qemu -drive if=none,id=disk -device lsi53c895a -device scsi-cd,drive=disk
+
+run_qemu -drive if=none,id=disk -device ide-drive,drive=disk
+run_qemu -drive if=none,id=disk -device ide-hd,drive=disk
+run_qemu -drive if=none,id=disk -device lsi53c895a -device scsi-disk,drive=disk
+run_qemu -drive if=none,id=disk -device lsi53c895a -device scsi-hd,drive=disk
+
+echo
+echo === Read-only ===
+echo
+
+run_qemu -drive file=$TEST_IMG,if=floppy,readonly=on
+run_qemu -drive file=$TEST_IMG,if=ide,media=cdrom,readonly=on
+run_qemu -drive file=$TEST_IMG,if=scsi,media=cdrom,readonly=on
+
+run_qemu -drive file=$TEST_IMG,if=ide,readonly=on
+run_qemu -drive file=$TEST_IMG,if=virtio,readonly=on
+run_qemu -drive file=$TEST_IMG,if=scsi,readonly=on
+
+run_qemu -drive file=$TEST_IMG,if=none,id=disk,readonly=on -device ide-cd,drive=disk
+run_qemu -drive file=$TEST_IMG,if=none,id=disk,readonly=on -device lsi53c895a -device scsi-cd,drive=disk
+
+run_qemu -drive file=$TEST_IMG,if=none,id=disk,readonly=on -device ide-drive,drive=disk
+run_qemu -drive file=$TEST_IMG,if=none,id=disk,readonly=on -device ide-hd,drive=disk
+run_qemu -drive file=$TEST_IMG,if=none,id=disk,readonly=on -device lsi53c895a -device scsi-disk,drive=disk
+run_qemu -drive file=$TEST_IMG,if=none,id=disk,readonly=on -device lsi53c895a -device scsi-hd,drive=disk
+
+echo
+echo === Cache modes ===
+echo
+
+# Cannot use the test image because cache=none might not work on the host FS
+# Use cdrom so that we won't get errors about missing media
+
+run_qemu -drive media=cdrom,cache=none
+run_qemu -drive media=cdrom,cache=directsync
+run_qemu -drive media=cdrom,cache=writeback
+run_qemu -drive media=cdrom,cache=writethrough
+run_qemu -drive media=cdrom,cache=unsafe
+run_qemu -drive media=cdrom,cache=invalid_value
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0
diff --git a/tests/qemu-iotests/051.out b/tests/qemu-iotests/051.out
new file mode 100644
index 0000000000..48456d5b07
--- /dev/null
+++ b/tests/qemu-iotests/051.out
@@ -0,0 +1,162 @@
+QA output created by 051
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
+
+=== Unknown option ===
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=: Block format 'qcow2' used by device 'ide0-hd0' doesn't support the option 'unknown_opt'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=on
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=on: Block format 'qcow2' used by device 'ide0-hd0' doesn't support the option 'unknown_opt'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=on: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=1234
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=1234: Block format 'qcow2' used by device 'ide0-hd0' doesn't support the option 'unknown_opt'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=1234: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=foo
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=foo: Block format 'qcow2' used by device 'ide0-hd0' doesn't support the option 'unknown_opt'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,unknown_opt=foo: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+
+=== Enable and disable lazy refcounting on the command line, plus some invalid values ===
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=on
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=off
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=: Parameter 'lazy_refcounts' expects 'on' or 'off'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=42
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=42: Parameter 'lazy_refcounts' expects 'on' or 'off'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=42: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=foo
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=foo: Parameter 'lazy_refcounts' expects 'on' or 'off'
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=foo: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+
+=== With version 2 images enabling lazy refcounts must fail ===
+
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=on
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=on: Lazy refcounts require a qcow2 image with at least qemu 1.1 compatibility level
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=on: could not open disk image TEST_DIR/t.qcow2: Invalid argument
+
+Testing: -drive file=TEST_DIR/t.qcow2,format=qcow2,lazy_refcounts=off
+qququiquit
+
+
+=== No medium ===
+
+Testing: -drive if=floppy
+qququiquit
+
+Testing: -drive if=ide,media=cdrom
+qququiquit
+
+Testing: -drive if=scsi,media=cdrom
+qququiquit
+
+Testing: -drive if=ide
+QEMU_PROG: Device needs media, but drive is empty
+QEMU_PROG: Initialization of device ide-hd failed
+
+Testing: -drive if=virtio
+QEMU_PROG: -drive if=virtio: Device needs media, but drive is empty
+QEMU_PROG: -drive if=virtio: Device 'virtio-blk-pci' could not be initialized
+
+Testing: -drive if=scsi
+QEMU_PROG: -drive if=scsi: Device needs media, but drive is empty
+QEMU_PROG: Initialization of device lsi53c895a failed
+
+Testing: -drive if=none,id=disk -device ide-cd,drive=disk
+qququiquit
+
+Testing: -drive if=none,id=disk -device lsi53c895a -device scsi-cd,drive=disk
+qququiquit
+
+Testing: -drive if=none,id=disk -device ide-drive,drive=disk
+QEMU_PROG: -device ide-drive,drive=disk: Device needs media, but drive is empty
+QEMU_PROG: -device ide-drive,drive=disk: Device 'ide-drive' could not be initialized
+
+Testing: -drive if=none,id=disk -device ide-hd,drive=disk
+QEMU_PROG: -device ide-hd,drive=disk: Device needs media, but drive is empty
+QEMU_PROG: -device ide-hd,drive=disk: Device 'ide-hd' could not be initialized
+
+Testing: -drive if=none,id=disk -device lsi53c895a -device scsi-disk,drive=disk
+QEMU_PROG: -device scsi-disk,drive=disk: Device needs media, but drive is empty
+QEMU_PROG: -device scsi-disk,drive=disk: Device 'scsi-disk' could not be initialized
+
+Testing: -drive if=none,id=disk -device lsi53c895a -device scsi-hd,drive=disk
+QEMU_PROG: -device scsi-hd,drive=disk: Device needs media, but drive is empty
+QEMU_PROG: -device scsi-hd,drive=disk: Device 'scsi-hd' could not be initialized
+
+
+=== Read-only ===
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=floppy,readonly=on
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=ide,media=cdrom,readonly=on
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=scsi,media=cdrom,readonly=on
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=ide,readonly=on
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,if=ide,readonly=on: readonly not supported by this bus type
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=virtio,readonly=on
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=scsi,readonly=on
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=none,id=disk,readonly=on -device ide-cd,drive=disk
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=none,id=disk,readonly=on -device lsi53c895a -device scsi-cd,drive=disk
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=none,id=disk,readonly=on -device ide-drive,drive=disk
+QEMU_PROG: -device ide-drive,drive=disk: Can't use a read-only drive
+QEMU_PROG: -device ide-drive,drive=disk: Device 'ide-drive' could not be initialized
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=none,id=disk,readonly=on -device ide-hd,drive=disk
+QEMU_PROG: -device ide-hd,drive=disk: Can't use a read-only drive
+QEMU_PROG: -device ide-hd,drive=disk: Device 'ide-hd' could not be initialized
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=none,id=disk,readonly=on -device lsi53c895a -device scsi-disk,drive=disk
+qququiquit
+
+Testing: -drive file=TEST_DIR/t.qcow2,if=none,id=disk,readonly=on -device lsi53c895a -device scsi-hd,drive=disk
+qququiquit
+
+
+=== Cache modes ===
+
+Testing: -drive media=cdrom,cache=none
+qququiquit
+
+Testing: -drive media=cdrom,cache=directsync
+qququiquit
+
+Testing: -drive media=cdrom,cache=writeback
+qququiquit
+
+Testing: -drive media=cdrom,cache=writethrough
+qququiquit
+
+Testing: -drive media=cdrom,cache=unsafe
+qququiquit
+
+Testing: -drive media=cdrom,cache=invalid_value
+QEMU_PROG: -drive media=cdrom,cache=invalid_value: invalid cache option
+
+*** done
diff --git a/tests/qemu-iotests/common b/tests/qemu-iotests/common
index b3aad89e2c..6826ea72fe 100644
--- a/tests/qemu-iotests/common
+++ b/tests/qemu-iotests/common
@@ -137,6 +137,7 @@ check options
     -rbd                test rbd
     -sheepdog           test sheepdog
     -nbd                test nbd
+    -ssh                test ssh
     -xdiff		graphical mode diff
     -nocache		use O_DIRECT on backing file
     -misalign		misalign memory allocations
@@ -206,6 +207,10 @@ testlist options
 	    IMGPROTO=nbd
 	    xpand=false
 	    ;;
+        -ssh)
+            IMGPROTO=ssh
+            xpand=false
+            ;;
 	-nocache)
 	    QEMU_IO_OPTIONS="$QEMU_IO_OPTIONS --nocache"
 	    xpand=false
diff --git a/tests/qemu-iotests/common.filter b/tests/qemu-iotests/common.filter
index fa26b62dd3..bc5f250cab 100644
--- a/tests/qemu-iotests/common.filter
+++ b/tests/qemu-iotests/common.filter
@@ -152,5 +152,11 @@ _filter_qemu_io()
     _filter_win32 | sed -e "s/[0-9]* ops\; [0-9/:. sec]* ([0-9/.inf]* [EPTGMKiBbytes]*\/sec and [0-9/.inf]* ops\/sec)/X ops\; XX:XX:XX.X (XXX YYY\/sec and XXX ops\/sec)/"
 }
 
+# replace occurrences of QEMU_PROG with "qemu"
+_filter_qemu()
+{
+    sed -e "s#$(basename $QEMU_PROG)#QEMU_PROG#g"
+}
+
 # make sure this script returns success
 /bin/true
diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
index e522d617aa..a536bf70a7 100644
--- a/tests/qemu-iotests/common.rc
+++ b/tests/qemu-iotests/common.rc
@@ -52,6 +52,9 @@ if [ "$IMGPROTO" = "file" ]; then
 elif [ "$IMGPROTO" = "nbd" ]; then
     TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
     TEST_IMG="nbd:127.0.0.1:10810"
+elif [ "$IMGPROTO" = "ssh" ]; then
+    TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
+    TEST_IMG="ssh://127.0.0.1$TEST_IMG_FILE"
 else
     TEST_IMG=$IMGPROTO:$TEST_DIR/t.$IMGFMT
 fi
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index 73c5966e10..324bacbcd4 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -57,4 +57,5 @@
 048 img auto quick
 049 rw auto
 050 rw auto backing quick
+051 rw auto
 052 rw auto backing