RE: [PATCH V2 23/23] [RFC] libxl: Add support for virtio-disk configuration

From: Wei Chen <Wei.Chen@arm.com>
To: Oleksandr Tyshchenko <olekstysh@gmail.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
	Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
	Anthony PERARD <anthony.perard@citrix.com>,
	Julien Grall <julien@xen.org>,
	Stefano Stabellini <sstabellini@kernel.org>
Subject: RE: [PATCH V2 23/23] [RFC] libxl: Add support for virtio-disk configuration
Date: Mon, 9 Nov 2020 06:45:49 +0000	[thread overview]
Message-ID: <AM0PR08MB374735F747FFF1A3016F37329EEA0@AM0PR08MB3747.eurprd08.prod.outlook.com> (raw)
In-Reply-To: <1602780274-29141-24-git-send-email-olekstysh@gmail.com>

Hi Oleksandr,

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of
> Oleksandr Tyshchenko
> Sent: 2020年10月16日 0:45
> To: xen-devel@lists.xenproject.org
> Cc: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>; Ian Jackson
> <iwj@xenproject.org>; Wei Liu <wl@xen.org>; Anthony PERARD
> <anthony.perard@citrix.com>; Julien Grall <julien@xen.org>; Stefano Stabellini
> <sstabellini@kernel.org>
> Subject: [PATCH V2 23/23] [RFC] libxl: Add support for virtio-disk configuration
> 
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> This patch adds basic support for configuring and assisting virtio-disk
> backend (emualator) which is intended to run out of Qemu and could be run
> in any domain.
> 
> Xenstore was chosen as a communication interface for the emulator running
> in non-toolstack domain to be able to get configuration either by reading
> Xenstore directly or by receiving command line parameters (an updated 'xl devd'
> running in the same domain would read Xenstore beforehand and call backend
> executable with the required arguments).
> 
> An example of domain configuration (two disks are assigned to the guest,
> the latter is in readonly mode):
> 
> vdisk = [ 'backend=DomD, disks=rw:/dev/mmcblk0p3;ro:/dev/mmcblk1p3' ]
> 

Can we keep use the same 'disk' parameter for virtio-disk, but add an option like
 "model=virtio-disk"?
For example:
disk = [ 'backend=DomD, disks=rw:/dev/mmcblk0p3,model=virtio-disk' ]
Just like what Xen has done for x86 virtio-net.

> Where per-disk Xenstore entries are:
> - filename and readonly flag (configured via "vdisk" property)
> - base and irq (allocated dynamically)
> 
> Besides handling 'visible' params described in configuration file,
> patch also allocates virtio-mmio specific ones for each device and
> writes them into Xenstore. virtio-mmio params (irq and base) are
> unique per guest domain, they allocated at the domain creation time
> and passed through to the emulator. Each VirtIO device has at least
> one pair of these params.
> 
> TODO:
> 1. An extra "virtio" property could be removed.
> 2. Update documentation.
> 
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> 
> ---
> Changes RFC -> V1:
>    - no changes
> 
> Changes V1 -> V2:
>    - rebase according to the new location of libxl_virtio_disk.c
> 
> Please note, there is a real concern about VirtIO interrupts allocation.
> Just copy here what Stefano said in RFC thread.
> 
> So, if we end up allocating let's say 6 virtio interrupts for a domain,
> the chance of a clash with a physical interrupt of a passthrough device is real.
> 
> I am not entirely sure how to solve it, but these are a few ideas:
> - choosing virtio interrupts that are less likely to conflict (maybe > 1000)
> - make the virtio irq (optionally) configurable so that a user could
>   override the default irq and specify one that doesn't conflict
> - implementing support for virq != pirq (even the xl interface doesn't
>   allow to specify the virq number for passthrough devices, see "irqs")
> 
> ---
>  tools/libs/light/Makefile                 |   1 +
>  tools/libs/light/libxl_arm.c              |  56 ++++++++++++---
>  tools/libs/light/libxl_create.c           |   1 +
>  tools/libs/light/libxl_internal.h         |   1 +
>  tools/libs/light/libxl_types.idl          |  15 ++++
>  tools/libs/light/libxl_types_internal.idl |   1 +
>  tools/libs/light/libxl_virtio_disk.c      | 109 ++++++++++++++++++++++++++++
>  tools/xl/Makefile                         |   2 +-
>  tools/xl/xl.h                             |   3 +
>  tools/xl/xl_cmdtable.c                    |  15 ++++
>  tools/xl/xl_parse.c                       | 115 ++++++++++++++++++++++++++++++
>  tools/xl/xl_virtio_disk.c                 |  46 ++++++++++++
>  12 files changed, 354 insertions(+), 11 deletions(-)
>  create mode 100644 tools/libs/light/libxl_virtio_disk.c
>  create mode 100644 tools/xl/xl_virtio_disk.c
> 
> diff --git a/tools/libs/light/Makefile b/tools/libs/light/Makefile
> index f58a321..2ee388a 100644
> --- a/tools/libs/light/Makefile
> +++ b/tools/libs/light/Makefile
> @@ -115,6 +115,7 @@ SRCS-y += libxl_genid.c
>  SRCS-y += _libxl_types.c
>  SRCS-y += libxl_flask.c
>  SRCS-y += _libxl_types_internal.c
> +SRCS-y += libxl_virtio_disk.c
> 
>  ifeq ($(CONFIG_LIBNL),y)
>  CFLAGS_LIBXL += $(LIBNL3_CFLAGS)
> diff --git a/tools/libs/light/libxl_arm.c b/tools/libs/light/libxl_arm.c
> index 588ee5a..9eb3022 100644
> --- a/tools/libs/light/libxl_arm.c
> +++ b/tools/libs/light/libxl_arm.c
> @@ -8,6 +8,12 @@
>  #include <assert.h>
>  #include <xen/device_tree_defs.h>
> 
> +#ifndef container_of
> +#define container_of(ptr, type, member) ({			\
> +        typeof( ((type *)0)->member ) *__mptr = (ptr);	\
> +        (type *)( (char *)__mptr - offsetof(type,member) );})
> +#endif
> +
>  static const char *gicv_to_string(libxl_gic_version gic_version)
>  {
>      switch (gic_version) {
> @@ -39,14 +45,32 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
>          vuart_enabled = true;
>      }
> 
> -    /*
> -     * XXX: Handle properly virtio
> -     * A proper solution would be the toolstack to allocate the interrupts
> -     * used by each virtio backend and let the backend now which one is used
> -     */
>      if (libxl_defbool_val(d_config->b_info.arch_arm.virtio)) {
> -        nr_spis += (GUEST_VIRTIO_MMIO_SPI - 32) + 1;
> +        uint64_t virtio_base;
> +        libxl_device_virtio_disk *virtio_disk;
> +
> +        virtio_base = GUEST_VIRTIO_MMIO_BASE;
>          virtio_irq = GUEST_VIRTIO_MMIO_SPI;
> +
> +        if (!d_config->num_virtio_disks) {
> +            LOG(ERROR, "Virtio is enabled, but no Virtio devices present\n");
> +            return ERROR_FAIL;
> +        }
> +        virtio_disk = &d_config->virtio_disks[0];
> +
> +        for (i = 0; i < virtio_disk->num_disks; i++) {
> +            virtio_disk->disks[i].base = virtio_base;
> +            virtio_disk->disks[i].irq = virtio_irq;
> +
> +            LOG(DEBUG, "Allocate Virtio MMIO params: IRQ %u BASE 0x%"PRIx64,
> +                virtio_irq, virtio_base);
> +
> +            virtio_irq ++;
> +            virtio_base += GUEST_VIRTIO_MMIO_SIZE;
> +        }
> +        virtio_irq --;
> +
> +        nr_spis += (virtio_irq - 32) + 1;
>          virtio_enabled = true;
>      }
> 
> @@ -70,8 +94,9 @@ int libxl__arch_domain_prepare_config(libxl__gc *gc,
>          }
> 
>          /* The same check as for vpl011 */
> -        if (virtio_enabled && irq == virtio_irq) {
> -            LOG(ERROR, "Physical IRQ %u conflicting with virtio SPI\n", irq);
> +        if (virtio_enabled &&
> +           (irq >= GUEST_VIRTIO_MMIO_SPI && irq <= virtio_irq)) {
> +            LOG(ERROR, "Physical IRQ %u conflicting with Virtio IRQ range\n", irq);
>              return ERROR_FAIL;
>          }
> 
> @@ -1011,8 +1036,19 @@ next_resize:
>          if (info->tee == LIBXL_TEE_TYPE_OPTEE)
>              FDT( make_optee_node(gc, fdt) );
> 
> -        if (libxl_defbool_val(info->arch_arm.virtio))
> -            FDT( make_virtio_mmio_node(gc, fdt, GUEST_VIRTIO_MMIO_BASE,
> GUEST_VIRTIO_MMIO_SPI) );
> +        if (libxl_defbool_val(info->arch_arm.virtio)) {
> +            libxl_domain_config *d_config =
> +                container_of(info, libxl_domain_config, b_info);
> +            libxl_device_virtio_disk *virtio_disk = &d_config->virtio_disks[0];
> +            unsigned int i;
> +
> +            for (i = 0; i < virtio_disk->num_disks; i++) {
> +                uint64_t base = virtio_disk->disks[i].base;
> +                uint32_t irq = virtio_disk->disks[i].irq;
> +
> +                FDT( make_virtio_mmio_node(gc, fdt, base, irq) );
> +            }
> +        }
> 
>          if (pfdt)
>              FDT( copy_partial_fdt(gc, fdt, pfdt) );
> diff --git a/tools/libs/light/libxl_create.c b/tools/libs/light/libxl_create.c
> index 321a13e..8da328d 100644
> --- a/tools/libs/light/libxl_create.c
> +++ b/tools/libs/light/libxl_create.c
> @@ -1821,6 +1821,7 @@ const libxl__device_type *device_type_tbl[] = {
>      &libxl__dtdev_devtype,
>      &libxl__vdispl_devtype,
>      &libxl__vsnd_devtype,
> +    &libxl__virtio_disk_devtype,
>      NULL
>  };
> 
> diff --git a/tools/libs/light/libxl_internal.h b/tools/libs/light/libxl_internal.h
> index e26cda9..ea497bb 100644
> --- a/tools/libs/light/libxl_internal.h
> +++ b/tools/libs/light/libxl_internal.h
> @@ -4000,6 +4000,7 @@ extern const libxl__device_type libxl__vdispl_devtype;
>  extern const libxl__device_type libxl__p9_devtype;
>  extern const libxl__device_type libxl__pvcallsif_devtype;
>  extern const libxl__device_type libxl__vsnd_devtype;
> +extern const libxl__device_type libxl__virtio_disk_devtype;
> 
>  extern const libxl__device_type *device_type_tbl[];
> 
> diff --git a/tools/libs/light/libxl_types.idl b/tools/libs/light/libxl_types.idl
> index b054bf9..5f8a3ff 100644
> --- a/tools/libs/light/libxl_types.idl
> +++ b/tools/libs/light/libxl_types.idl
> @@ -935,6 +935,20 @@ libxl_device_vsnd = Struct("device_vsnd", [
>      ("pcms", Array(libxl_vsnd_pcm, "num_vsnd_pcms"))
>      ])
> 
> +libxl_virtio_disk_param = Struct("virtio_disk_param", [
> +    ("filename", string),
> +    ("readonly", bool),
> +    ("irq", uint32),
> +    ("base", uint64),
> +    ])
> +
> +libxl_device_virtio_disk = Struct("device_virtio_disk", [
> +    ("backend_domid", libxl_domid),
> +    ("backend_domname", string),
> +    ("devid", libxl_devid),
> +    ("disks", Array(libxl_virtio_disk_param, "num_disks")),
> +    ])
> +
>  libxl_domain_config = Struct("domain_config", [
>      ("c_info", libxl_domain_create_info),
>      ("b_info", libxl_domain_build_info),
> @@ -951,6 +965,7 @@ libxl_domain_config = Struct("domain_config", [
>      ("pvcallsifs", Array(libxl_device_pvcallsif, "num_pvcallsifs")),
>      ("vdispls", Array(libxl_device_vdispl, "num_vdispls")),
>      ("vsnds", Array(libxl_device_vsnd, "num_vsnds")),
> +    ("virtio_disks", Array(libxl_device_virtio_disk, "num_virtio_disks")),
>      # a channel manifests as a console with a name,
>      # see docs/misc/channels.txt
>      ("channels", Array(libxl_device_channel, "num_channels")),
> diff --git a/tools/libs/light/libxl_types_internal.idl
> b/tools/libs/light/libxl_types_internal.idl
> index 3593e21..8f71980 100644
> --- a/tools/libs/light/libxl_types_internal.idl
> +++ b/tools/libs/light/libxl_types_internal.idl
> @@ -32,6 +32,7 @@ libxl__device_kind = Enumeration("device_kind", [
>      (14, "PVCALLS"),
>      (15, "VSND"),
>      (16, "VINPUT"),
> +    (17, "VIRTIO_DISK"),
>      ])
> 
>  libxl__console_backend = Enumeration("console_backend", [
> diff --git a/tools/libs/light/libxl_virtio_disk.c b/tools/libs/light/libxl_virtio_disk.c
> new file mode 100644
> index 0000000..25e7f1a
> --- /dev/null
> +++ b/tools/libs/light/libxl_virtio_disk.c
> @@ -0,0 +1,109 @@
> +/*
> + * Copyright (C) 2020 EPAM Systems Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published
> + * by the Free Software Foundation; version 2.1 only. with the special
> + * exception on linking described in file LICENSE.
> + *
> + * 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 Lesser General Public License for more details.
> + */
> +
> +#include "libxl_internal.h"
> +
> +static int libxl__device_virtio_disk_setdefault(libxl__gc *gc, uint32_t domid,
> +                                                libxl_device_virtio_disk *virtio_disk,
> +                                                bool hotplug)
> +{
> +    return libxl__resolve_domid(gc, virtio_disk->backend_domname,
> +                                &virtio_disk->backend_domid);
> +}
> +
> +static int libxl__virtio_disk_from_xenstore(libxl__gc *gc, const char *libxl_path,
> +                                            libxl_devid devid,
> +                                            libxl_device_virtio_disk *virtio_disk)
> +{
> +    const char *be_path;
> +    int rc;
> +
> +    virtio_disk->devid = devid;
> +    rc = libxl__xs_read_mandatory(gc, XBT_NULL,
> +                                  GCSPRINTF("%s/backend", libxl_path),
> +                                  &be_path);
> +    if (rc) return rc;
> +
> +    rc = libxl__backendpath_parse_domid(gc, be_path, &virtio_disk-
> >backend_domid);
> +    if (rc) return rc;
> +
> +    return 0;
> +}
> +
> +static void libxl__update_config_virtio_disk(libxl__gc *gc,
> +                                             libxl_device_virtio_disk *dst,
> +                                             libxl_device_virtio_disk *src)
> +{
> +    dst->devid = src->devid;
> +}
> +
> +static int libxl_device_virtio_disk_compare(libxl_device_virtio_disk *d1,
> +                                            libxl_device_virtio_disk *d2)
> +{
> +    return COMPARE_DEVID(d1, d2);
> +}
> +
> +static void libxl__device_virtio_disk_add(libxl__egc *egc, uint32_t domid,
> +                                          libxl_device_virtio_disk *virtio_disk,
> +                                          libxl__ao_device *aodev)
> +{
> +    libxl__device_add_async(egc, domid, &libxl__virtio_disk_devtype, virtio_disk,
> aodev);
> +}
> +
> +static int libxl__set_xenstore_virtio_disk(libxl__gc *gc, uint32_t domid,
> +                                           libxl_device_virtio_disk *virtio_disk,
> +                                           flexarray_t *back, flexarray_t *front,
> +                                           flexarray_t *ro_front)
> +{
> +    int rc;
> +    unsigned int i;
> +
> +    for (i = 0; i < virtio_disk->num_disks; i++) {
> +        rc = flexarray_append_pair(ro_front, GCSPRINTF("%d/filename", i),
> +                                   GCSPRINTF("%s", virtio_disk->disks[i].filename));
> +        if (rc) return rc;
> +
> +        rc = flexarray_append_pair(ro_front, GCSPRINTF("%d/readonly", i),
> +                                   GCSPRINTF("%d", virtio_disk->disks[i].readonly));
> +        if (rc) return rc;
> +
> +        rc = flexarray_append_pair(ro_front, GCSPRINTF("%d/base", i),
> +                                   GCSPRINTF("%lu", virtio_disk->disks[i].base));
> +        if (rc) return rc;
> +
> +        rc = flexarray_append_pair(ro_front, GCSPRINTF("%d/irq", i),
> +                                   GCSPRINTF("%u", virtio_disk->disks[i].irq));
> +        if (rc) return rc;
> +    }
> +
> +    return 0;
> +}
> +
> +static LIBXL_DEFINE_UPDATE_DEVID(virtio_disk)
> +static LIBXL_DEFINE_DEVICE_FROM_TYPE(virtio_disk)
> +static LIBXL_DEFINE_DEVICES_ADD(virtio_disk)
> +
> +DEFINE_DEVICE_TYPE_STRUCT(virtio_disk, VIRTIO_DISK,
> +    .update_config = (device_update_config_fn_t)
> libxl__update_config_virtio_disk,
> +    .from_xenstore = (device_from_xenstore_fn_t)
> libxl__virtio_disk_from_xenstore,
> +    .set_xenstore_config = (device_set_xenstore_config_fn_t)
> libxl__set_xenstore_virtio_disk
> +);
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/tools/xl/Makefile b/tools/xl/Makefile
> index bdf67c8..9d8f2aa 100644
> --- a/tools/xl/Makefile
> +++ b/tools/xl/Makefile
> @@ -23,7 +23,7 @@ XL_OBJS += xl_vtpm.o xl_block.o xl_nic.o xl_usb.o
>  XL_OBJS += xl_sched.o xl_pci.o xl_vcpu.o xl_cdrom.o xl_mem.o
>  XL_OBJS += xl_info.o xl_console.o xl_misc.o
>  XL_OBJS += xl_vmcontrol.o xl_saverestore.o xl_migrate.o
> -XL_OBJS += xl_vdispl.o xl_vsnd.o xl_vkb.o
> +XL_OBJS += xl_vdispl.o xl_vsnd.o xl_vkb.o xl_virtio_disk.o
> 
>  $(XL_OBJS): CFLAGS += $(CFLAGS_libxentoollog)
>  $(XL_OBJS): CFLAGS += $(CFLAGS_XL)
> diff --git a/tools/xl/xl.h b/tools/xl/xl.h
> index 06569c6..3d26f19 100644
> --- a/tools/xl/xl.h
> +++ b/tools/xl/xl.h
> @@ -178,6 +178,9 @@ int main_vsnddetach(int argc, char **argv);
>  int main_vkbattach(int argc, char **argv);
>  int main_vkblist(int argc, char **argv);
>  int main_vkbdetach(int argc, char **argv);
> +int main_virtio_diskattach(int argc, char **argv);
> +int main_virtio_disklist(int argc, char **argv);
> +int main_virtio_diskdetach(int argc, char **argv);
>  int main_usbctrl_attach(int argc, char **argv);
>  int main_usbctrl_detach(int argc, char **argv);
>  int main_usbdev_attach(int argc, char **argv);
> diff --git a/tools/xl/xl_cmdtable.c b/tools/xl/xl_cmdtable.c
> index 7da6c1b..745afab 100644
> --- a/tools/xl/xl_cmdtable.c
> +++ b/tools/xl/xl_cmdtable.c
> @@ -435,6 +435,21 @@ struct cmd_spec cmd_table[] = {
>        "Destroy a domain's virtual sound device",
>        "<Domain> <DevId>",
>      },
> +    { "virtio-disk-attach",
> +      &main_virtio_diskattach, 1, 1,
> +      "Create a new virtio block device",
> +      " TBD\n"
> +    },
> +    { "virtio-disk-list",
> +      &main_virtio_disklist, 0, 0,
> +      "List virtio block devices for a domain",
> +      "<Domain(s)>",
> +    },
> +    { "virtio-disk-detach",
> +      &main_virtio_diskdetach, 0, 1,
> +      "Destroy a domain's virtio block device",
> +      "<Domain> <DevId>",
> +    },
>      { "uptime",
>        &main_uptime, 0, 0,
>        "Print uptime for all/some domains",
> diff --git a/tools/xl/xl_parse.c b/tools/xl/xl_parse.c
> index 10acf22..6cf3524 100644
> --- a/tools/xl/xl_parse.c
> +++ b/tools/xl/xl_parse.c
> @@ -1204,6 +1204,120 @@ out:
>      if (rc) exit(EXIT_FAILURE);
>  }
> 
> +#define MAX_VIRTIO_DISKS 4
> +
> +static int parse_virtio_disk_config(libxl_device_virtio_disk *virtio_disk, char
> *token)
> +{
> +    char *oparg;
> +    libxl_string_list disks = NULL;
> +    int i, rc;
> +
> +    if (MATCH_OPTION("backend", token, oparg)) {
> +        virtio_disk->backend_domname = strdup(oparg);
> +    } else if (MATCH_OPTION("disks", token, oparg)) {
> +        split_string_into_string_list(oparg, ";", &disks);
> +
> +        virtio_disk->num_disks = libxl_string_list_length(&disks);
> +        if (virtio_disk->num_disks > MAX_VIRTIO_DISKS) {
> +            fprintf(stderr, "vdisk: currently only %d disks are supported",
> +                    MAX_VIRTIO_DISKS);
> +            return 1;
> +        }
> +        virtio_disk->disks = xcalloc(virtio_disk->num_disks,
> +                                     sizeof(*virtio_disk->disks));
> +
> +        for(i = 0; i < virtio_disk->num_disks; i++) {
> +            char *disk_opt;
> +
> +            rc = split_string_into_pair(disks[i], ":", &disk_opt,
> +                                        &virtio_disk->disks[i].filename);
> +            if (rc) {
> +                fprintf(stderr, "vdisk: failed to split \"%s\" into pair\n",
> +                        disks[i]);
> +                goto out;
> +            }
> +
> +            if (!strcmp(disk_opt, "ro"))
> +                virtio_disk->disks[i].readonly = 1;
> +            else if (!strcmp(disk_opt, "rw"))
> +                virtio_disk->disks[i].readonly = 0;
> +            else {
> +                fprintf(stderr, "vdisk: failed to parse \"%s\" disk option\n",
> +                        disk_opt);
> +                rc = 1;
> +            }
> +            free(disk_opt);
> +
> +            if (rc) goto out;
> +        }
> +    } else {
> +        fprintf(stderr, "Unknown string \"%s\" in vdisk spec\n", token);
> +        rc = 1; goto out;
> +    }
> +
> +    rc = 0;
> +
> +out:
> +    libxl_string_list_dispose(&disks);
> +    return rc;
> +}
> +
> +static void parse_virtio_disk_list(const XLU_Config *config,
> +                            libxl_domain_config *d_config)
> +{
> +    XLU_ConfigList *virtio_disks;
> +    const char *item;
> +    char *buf = NULL;
> +    int rc;
> +
> +    if (!xlu_cfg_get_list (config, "vdisk", &virtio_disks, 0, 0)) {
> +        libxl_domain_build_info *b_info = &d_config->b_info;
> +        int entry = 0;
> +
> +        /* XXX Remove an extra property */
> +        libxl_defbool_setdefault(&b_info->arch_arm.virtio, false);
> +        if (!libxl_defbool_val(b_info->arch_arm.virtio)) {
> +            fprintf(stderr, "Virtio device requires Virtio property to be set\n");
> +            exit(EXIT_FAILURE);
> +        }
> +
> +        while ((item = xlu_cfg_get_listitem(virtio_disks, entry)) != NULL) {
> +            libxl_device_virtio_disk *virtio_disk;
> +            char *p;
> +
> +            virtio_disk = ARRAY_EXTEND_INIT(d_config->virtio_disks,
> +                                            d_config->num_virtio_disks,
> +                                            libxl_device_virtio_disk_init);
> +
> +            buf = strdup(item);
> +
> +            p = strtok (buf, ",");
> +            while (p != NULL)
> +            {
> +                while (*p == ' ') p++;
> +
> +                rc = parse_virtio_disk_config(virtio_disk, p);
> +                if (rc) goto out;
> +
> +                p = strtok (NULL, ",");
> +            }
> +
> +            entry++;
> +
> +            if (virtio_disk->num_disks == 0) {
> +                fprintf(stderr, "At least one virtio disk should be specified\n");
> +                rc = 1; goto out;
> +            }
> +        }
> +    }
> +
> +    rc = 0;
> +
> +out:
> +    free(buf);
> +    if (rc) exit(EXIT_FAILURE);
> +}
> +
>  void parse_config_data(const char *config_source,
>                         const char *config_data,
>                         int config_len,
> @@ -2734,6 +2848,7 @@ skip_usbdev:
>      }
> 
>      parse_vkb_list(config, d_config);
> +    parse_virtio_disk_list(config, d_config);
> 
>      xlu_cfg_get_defbool(config, "xend_suspend_evtchn_compat",
>                          &c_info->xend_suspend_evtchn_compat, 0);
> diff --git a/tools/xl/xl_virtio_disk.c b/tools/xl/xl_virtio_disk.c
> new file mode 100644
> index 0000000..808a7da
> --- /dev/null
> +++ b/tools/xl/xl_virtio_disk.c
> @@ -0,0 +1,46 @@
> +/*
> + * Copyright (C) 2020 EPAM Systems Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU Lesser General Public License as published
> + * by the Free Software Foundation; version 2.1 only. with the special
> + * exception on linking described in file LICENSE.
> + *
> + * 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 Lesser General Public License for more details.
> + */
> +
> +#include <stdlib.h>
> +
> +#include <libxl.h>
> +#include <libxl_utils.h>
> +#include <libxlutil.h>
> +
> +#include "xl.h"
> +#include "xl_utils.h"
> +#include "xl_parse.h"
> +
> +int main_virtio_diskattach(int argc, char **argv)
> +{
> +    return 0;
> +}
> +
> +int main_virtio_disklist(int argc, char **argv)
> +{
> +   return 0;
> +}
> +
> +int main_virtio_diskdetach(int argc, char **argv)
> +{
> +    return 0;
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> --
> 2.7.4
> 