Re: [Qemu-block] [PATCH 03/18] xen: introduce 'xen-qdisk'
> -Original Message-
> From: Qemu-devel [mailto:qemu-devel-
> bounces+paul.durrant=citrix@nongnu.org] On Behalf Of Paul Durrant
> Sent: 04 December 2018 15:20
> To: Anthony Perard
> Cc: Kevin Wolf ; Stefano Stabellini
> ; qemu-block@nongnu.org; qemu-de...@nongnu.org;
> Max Reitz ; xen-de...@lists.xenproject.org
> Subject: Re: [Qemu-devel] [PATCH 03/18] xen: introduce 'xen-qdisk'
>
> > -Original Message-
> > From: Anthony PERARD [mailto:anthony.per...@citrix.com]
> > Sent: 29 November 2018 16:06
> > To: Paul Durrant
> > Cc: qemu-block@nongnu.org; qemu-de...@nongnu.org; xen-
> > de...@lists.xenproject.org; Kevin Wolf ; Max Reitz
> > ; Stefano Stabellini
> > Subject: Re: [PATCH 03/18] xen: introduce 'xen-qdisk'
> >
> > On Wed, Nov 21, 2018 at 03:11:56PM +, Paul Durrant wrote:
> > > This patch adds a new XenDevice: 'xen-qdisk' [1]. This will eventually
> > > replace the 'xen_disk' legacy PV backend but it is illustrative to
> build
> > > up the implementation incrementally, along with the XenBus/XenDevice
> > > framework. Subsequent patches will therefore add to this device's
> > > implementation as new features are added to the framework.
> > >
> > > After this patch has been applied it is possible to instantiate a new
> > > 'xen-qdisk' device with a single 'vdev' parameter, which accepts
> values
> > > adhering to the Xen VBD naming scheme [2]. For example, a command-line
> > > instantiation of a xen-qdisk can be done with an argument similar to
> the
> > > following:
> > >
> > > -device xen-qdisk,vdev=hda
> >
> > That works when QEMU boot, but doing the same thing once the guest have
> > booted, via QMP, doesn't. Here is the result (tested in qmp-shell):
> >
> > (QEMU) device_add driver=xen-qdisk vdev=hda
> > {
> > "error": {
> > "class": "GenericError",
> > "desc": "Bus 'xen-bus.0' does not support hotplugging"
> > }
> > }
> >
> > That's probably why I've asked about the hotplug capability on the
> > previous patch.
> >
>
> Ok. I've added the hotplug now so I'll make sure QMP DTRT.
>
> > > The implementation of the vdev parameter formulates the appropriate
> VBD
> > > number for use in the PV protocol.
> > >
> > > [1] The name 'qdisk' as always been the name given to the QEMU
> > > implementation of the Xen PV block protocol backend implementation
> > > [2] http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xen-
> vbd-
> > interface.markdown.7
> >
> > Maybe a link to the generated docs would be better:
> > https://xenbits.xen.org/docs/unstable/man/xen-vbd-interface.7.html
> >
>
> Ok.
>
> > Also, it would be useful to have the same link in the source code.
> >
>
> Yes, I'll add a comment.
>
> > > diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c
> > > new file mode 100644
> > > index 00..72122073f7
> > > --- /dev/null
> > > +++ b/hw/block/xen-qdisk.c
> > [...]
> > > +static char *disk_to_vbd_name(unsigned int disk)
> > > +{
> > > +unsigned int len = DIV_ROUND_UP(disk, 26);
> > > +char *name = g_malloc0(len + 1);
> > > +
> > > +do {
> > > +name[len--] = 'a' + (disk % 26);
> > > +disk /= 26;
> > > +} while (disk != 0);
> > > +assert(len == 0);
> > > +
> > > +return name;
> > > +}
> >
> > That function doesn't work.
> >
> > For a simple xvdp, (so disk==15), it return "", I mean "\0p".
> >
> > For a more complicated 'xvdbhwza', we have len == 22901. And the assert
> > failed.
> >
> > Maybe the recursing algo in libxl would be fine, with a buffer that is
> > big enough, and could probably be on the stack (in _get_vdev).
>
> I used libxl__device_disk_dev_number() as my model (as well as cross-
> checking with the spec), but I guess a recursing algorithm would be
> neater.
>
> >
> > > +
> > > +switch (vdev->type) {
> > > +case XEN_QDISK_VDEV_TYPE_DP:
> > > +case XEN_QDISK_VDEV_TYPE_XVD:
> > > +if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
> > > +vdev->number = (202 << 8) | (vdev->disk << 4) |
> > > +vdev->partition;
> > > +} else if (vdev->disk < (1 << 20) && vdev->partition < (1 <<
> > 8)) {
> > > +vdev->number = (1 << 28) | (vdev->disk << 8) |
> > > +vdev->partition;
> > > +} else {
> > > +goto invalid;
> > > +}
> > > +break;
> > > +
> > > +case XEN_QDISK_VDEV_TYPE_HD:
> > > +if ((vdev->disk == 0 || vdev->disk == 1) &&
> > > +vdev->partition < (1 << 4)) {
> >
> > I think that should be:
> >
> > vdev->partition < (1 << 6)
> >
> > Because hd disk have 0..63 partitions.
>
> Yes, I must have typo-ed it...
>
> >
> > > +vdev->number = (3 << 8) | (vdev->disk << 6) | vdev-
> > >partition;
> > > +} else if ((vdev->disk == 2 || vdev->disk == 3) &&
> > > + vdev->partition < (1 << 4)) {
> >
> > same here.
>
> ...and then cut'n'pasted.
>
> >
> > > +vdev->number = (22 << 8) | ((vdev->disk
Re: [Qemu-block] [PATCH 03/18] xen: introduce 'xen-qdisk'
> -Original Message-
> From: Anthony PERARD [mailto:anthony.per...@citrix.com]
> Sent: 04 December 2018 15:49
> To: Paul Durrant
> Cc: qemu-block@nongnu.org; qemu-de...@nongnu.org; xen-
> de...@lists.xenproject.org; Kevin Wolf ; Max Reitz
> ; Stefano Stabellini
> Subject: Re: [PATCH 03/18] xen: introduce 'xen-qdisk'
>
> On Tue, Dec 04, 2018 at 03:20:04PM +, Paul Durrant wrote:
> > > > +static char *disk_to_vbd_name(unsigned int disk)
> > > > +{
> > > > +unsigned int len = DIV_ROUND_UP(disk, 26);
> > > > +char *name = g_malloc0(len + 1);
> > > > +
> > > > +do {
> > > > +name[len--] = 'a' + (disk % 26);
> > > > +disk /= 26;
> > > > +} while (disk != 0);
> > > > +assert(len == 0);
> > > > +
> > > > +return name;
> > > > +}
> > >
> > > That function doesn't work.
> > >
> > > For a simple xvdp, (so disk==15), it return "", I mean "\0p".
> > >
> > > For a more complicated 'xvdbhwza', we have len == 22901. And the
> assert
> > > failed.
> > >
> > > Maybe the recursing algo in libxl would be fine, with a buffer that is
> > > big enough, and could probably be on the stack (in _get_vdev).
> >
> > I used libxl__device_disk_dev_number() as my model (as well as cross-
> checking with the spec), but I guess a recursing algorithm would be
> neater.
>
> There is libxl__devid_to_vdev() actually just after ;-) which calls
> encode_disk_name which is recursing.
Ah, I'll look for that. Currently having trouble reconciling the 'tq' -> 536
mapping in the doc.
Paul
>
> > > > diff --git a/include/hw/xen/xen-qdisk.h b/include/hw/xen/xen-qdisk.h
> > > > new file mode 100644
> > > > index 00..ade0866037
> > > > --- /dev/null
> > > > +++ b/include/hw/xen/xen-qdisk.h
> > > > @@ -0,0 +1,38 @@
> > > > +/*
> > > > + * Copyright (c) Citrix Systems Inc.
> > > > + * All rights reserved.
> > > > + */
> > > > +
> > > > +#ifndef HW_XEN_QDISK_H
> > > > +#define HW_XEN_QDISK_H
> > > > +
> > > > +#include "hw/xen/xen-bus.h"
> > > > +
> > > > +typedef enum XenQdiskVdevType {
> > > > +XEN_QDISK_VDEV_TYPE_DP,
> > >
> > > Maybe we could set type_dp value to 1, so that, when vdev->type isn't
> > > set, we can detect it later.
> >
> > Rather than having the 'valid' bool? Yes, that would work.
>
> Well, the 'valid' bool doesn't seems to always be check so it would be
> better. e.g. xen_qdisk_get_vdev() doesn't check `valid` before
> genereting a string. Then xen_qdisk_set_vdev could set `type` to invalid
> when it is invalid.
>
> --
> Anthony PERARD
Re: [Qemu-block] [PATCH 03/18] xen: introduce 'xen-qdisk'
On Tue, Dec 04, 2018 at 03:20:04PM +, Paul Durrant wrote:
> > > +static char *disk_to_vbd_name(unsigned int disk)
> > > +{
> > > +unsigned int len = DIV_ROUND_UP(disk, 26);
> > > +char *name = g_malloc0(len + 1);
> > > +
> > > +do {
> > > +name[len--] = 'a' + (disk % 26);
> > > +disk /= 26;
> > > +} while (disk != 0);
> > > +assert(len == 0);
> > > +
> > > +return name;
> > > +}
> >
> > That function doesn't work.
> >
> > For a simple xvdp, (so disk==15), it return "", I mean "\0p".
> >
> > For a more complicated 'xvdbhwza', we have len == 22901. And the assert
> > failed.
> >
> > Maybe the recursing algo in libxl would be fine, with a buffer that is
> > big enough, and could probably be on the stack (in _get_vdev).
>
> I used libxl__device_disk_dev_number() as my model (as well as cross-checking
> with the spec), but I guess a recursing algorithm would be neater.
There is libxl__devid_to_vdev() actually just after ;-) which calls
encode_disk_name which is recursing.
> > > diff --git a/include/hw/xen/xen-qdisk.h b/include/hw/xen/xen-qdisk.h
> > > new file mode 100644
> > > index 00..ade0866037
> > > --- /dev/null
> > > +++ b/include/hw/xen/xen-qdisk.h
> > > @@ -0,0 +1,38 @@
> > > +/*
> > > + * Copyright (c) Citrix Systems Inc.
> > > + * All rights reserved.
> > > + */
> > > +
> > > +#ifndef HW_XEN_QDISK_H
> > > +#define HW_XEN_QDISK_H
> > > +
> > > +#include "hw/xen/xen-bus.h"
> > > +
> > > +typedef enum XenQdiskVdevType {
> > > +XEN_QDISK_VDEV_TYPE_DP,
> >
> > Maybe we could set type_dp value to 1, so that, when vdev->type isn't
> > set, we can detect it later.
>
> Rather than having the 'valid' bool? Yes, that would work.
Well, the 'valid' bool doesn't seems to always be check so it would be
better. e.g. xen_qdisk_get_vdev() doesn't check `valid` before
genereting a string. Then xen_qdisk_set_vdev could set `type` to invalid
when it is invalid.
--
Anthony PERARD
Re: [Qemu-block] [PATCH 03/18] xen: introduce 'xen-qdisk'
> -Original Message-
> From: Anthony PERARD [mailto:anthony.per...@citrix.com]
> Sent: 29 November 2018 16:06
> To: Paul Durrant
> Cc: qemu-block@nongnu.org; qemu-de...@nongnu.org; xen-
> de...@lists.xenproject.org; Kevin Wolf ; Max Reitz
> ; Stefano Stabellini
> Subject: Re: [PATCH 03/18] xen: introduce 'xen-qdisk'
>
> On Wed, Nov 21, 2018 at 03:11:56PM +, Paul Durrant wrote:
> > This patch adds a new XenDevice: 'xen-qdisk' [1]. This will eventually
> > replace the 'xen_disk' legacy PV backend but it is illustrative to build
> > up the implementation incrementally, along with the XenBus/XenDevice
> > framework. Subsequent patches will therefore add to this device's
> > implementation as new features are added to the framework.
> >
> > After this patch has been applied it is possible to instantiate a new
> > 'xen-qdisk' device with a single 'vdev' parameter, which accepts values
> > adhering to the Xen VBD naming scheme [2]. For example, a command-line
> > instantiation of a xen-qdisk can be done with an argument similar to the
> > following:
> >
> > -device xen-qdisk,vdev=hda
>
> That works when QEMU boot, but doing the same thing once the guest have
> booted, via QMP, doesn't. Here is the result (tested in qmp-shell):
>
> (QEMU) device_add driver=xen-qdisk vdev=hda
> {
> "error": {
> "class": "GenericError",
> "desc": "Bus 'xen-bus.0' does not support hotplugging"
> }
> }
>
> That's probably why I've asked about the hotplug capability on the
> previous patch.
>
Ok. I've added the hotplug now so I'll make sure QMP DTRT.
> > The implementation of the vdev parameter formulates the appropriate VBD
> > number for use in the PV protocol.
> >
> > [1] The name 'qdisk' as always been the name given to the QEMU
> > implementation of the Xen PV block protocol backend implementation
> > [2] http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xen-vbd-
> interface.markdown.7
>
> Maybe a link to the generated docs would be better:
> https://xenbits.xen.org/docs/unstable/man/xen-vbd-interface.7.html
>
Ok.
> Also, it would be useful to have the same link in the source code.
>
Yes, I'll add a comment.
> > diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c
> > new file mode 100644
> > index 00..72122073f7
> > --- /dev/null
> > +++ b/hw/block/xen-qdisk.c
> [...]
> > +static char *disk_to_vbd_name(unsigned int disk)
> > +{
> > +unsigned int len = DIV_ROUND_UP(disk, 26);
> > +char *name = g_malloc0(len + 1);
> > +
> > +do {
> > +name[len--] = 'a' + (disk % 26);
> > +disk /= 26;
> > +} while (disk != 0);
> > +assert(len == 0);
> > +
> > +return name;
> > +}
>
> That function doesn't work.
>
> For a simple xvdp, (so disk==15), it return "", I mean "\0p".
>
> For a more complicated 'xvdbhwza', we have len == 22901. And the assert
> failed.
>
> Maybe the recursing algo in libxl would be fine, with a buffer that is
> big enough, and could probably be on the stack (in _get_vdev).
I used libxl__device_disk_dev_number() as my model (as well as cross-checking
with the spec), but I guess a recursing algorithm would be neater.
>
> > +
> > +switch (vdev->type) {
> > +case XEN_QDISK_VDEV_TYPE_DP:
> > +case XEN_QDISK_VDEV_TYPE_XVD:
> > +if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
> > +vdev->number = (202 << 8) | (vdev->disk << 4) |
> > +vdev->partition;
> > +} else if (vdev->disk < (1 << 20) && vdev->partition < (1 <<
> 8)) {
> > +vdev->number = (1 << 28) | (vdev->disk << 8) |
> > +vdev->partition;
> > +} else {
> > +goto invalid;
> > +}
> > +break;
> > +
> > +case XEN_QDISK_VDEV_TYPE_HD:
> > +if ((vdev->disk == 0 || vdev->disk == 1) &&
> > +vdev->partition < (1 << 4)) {
>
> I think that should be:
>
> vdev->partition < (1 << 6)
>
> Because hd disk have 0..63 partitions.
Yes, I must have typo-ed it...
>
> > +vdev->number = (3 << 8) | (vdev->disk << 6) | vdev-
> >partition;
> > +} else if ((vdev->disk == 2 || vdev->disk == 3) &&
> > + vdev->partition < (1 << 4)) {
>
> same here.
...and then cut'n'pasted.
>
> > +vdev->number = (22 << 8) | ((vdev->disk - 2) << 6) |
> > +vdev->partition;
> > +} else {
> > +goto invalid;
> > +}
> > +break;
> > +
> > +case XEN_QDISK_VDEV_TYPE_SD:
> > +if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
> > +vdev->number = (8 << 8) | (vdev->disk << 4) | vdev-
> >partition;
> > +} else {
> > +goto invalid;
> > +}
> > +break;
> > +
> > +default:
> > +goto invalid;
> > +}
> > +
> > +g_free(str);
> > +vdev->valid = true;
> > +return;
> > +
> > +invalid:
> > +error_setg(errp, "invalid virtual disk specifier");
> > +
Re: [Qemu-block] [PATCH 03/18] xen: introduce 'xen-qdisk'
On Wed, Nov 21, 2018 at 03:11:56PM +, Paul Durrant wrote:
> This patch adds a new XenDevice: 'xen-qdisk' [1]. This will eventually
> replace the 'xen_disk' legacy PV backend but it is illustrative to build
> up the implementation incrementally, along with the XenBus/XenDevice
> framework. Subsequent patches will therefore add to this device's
> implementation as new features are added to the framework.
>
> After this patch has been applied it is possible to instantiate a new
> 'xen-qdisk' device with a single 'vdev' parameter, which accepts values
> adhering to the Xen VBD naming scheme [2]. For example, a command-line
> instantiation of a xen-qdisk can be done with an argument similar to the
> following:
>
> -device xen-qdisk,vdev=hda
That works when QEMU boot, but doing the same thing once the guest have
booted, via QMP, doesn't. Here is the result (tested in qmp-shell):
(QEMU) device_add driver=xen-qdisk vdev=hda
{
"error": {
"class": "GenericError",
"desc": "Bus 'xen-bus.0' does not support hotplugging"
}
}
That's probably why I've asked about the hotplug capability on the
previous patch.
> The implementation of the vdev parameter formulates the appropriate VBD
> number for use in the PV protocol.
>
> [1] The name 'qdisk' as always been the name given to the QEMU
> implementation of the Xen PV block protocol backend implementation
> [2]
> http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xen-vbd-interface.markdown.7
Maybe a link to the generated docs would be better:
https://xenbits.xen.org/docs/unstable/man/xen-vbd-interface.7.html
Also, it would be useful to have the same link in the source code.
> diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c
> new file mode 100644
> index 00..72122073f7
> --- /dev/null
> +++ b/hw/block/xen-qdisk.c
[...]
> +static char *disk_to_vbd_name(unsigned int disk)
> +{
> +unsigned int len = DIV_ROUND_UP(disk, 26);
> +char *name = g_malloc0(len + 1);
> +
> +do {
> +name[len--] = 'a' + (disk % 26);
> +disk /= 26;
> +} while (disk != 0);
> +assert(len == 0);
> +
> +return name;
> +}
That function doesn't work.
For a simple xvdp, (so disk==15), it return "", I mean "\0p".
For a more complicated 'xvdbhwza', we have len == 22901. And the assert failed.
Maybe the recursing algo in libxl would be fine, with a buffer that is
big enough, and could probably be on the stack (in _get_vdev).
> +
> +switch (vdev->type) {
> +case XEN_QDISK_VDEV_TYPE_DP:
> +case XEN_QDISK_VDEV_TYPE_XVD:
> +if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
> +vdev->number = (202 << 8) | (vdev->disk << 4) |
> +vdev->partition;
> +} else if (vdev->disk < (1 << 20) && vdev->partition < (1 << 8)) {
> +vdev->number = (1 << 28) | (vdev->disk << 8) |
> +vdev->partition;
> +} else {
> +goto invalid;
> +}
> +break;
> +
> +case XEN_QDISK_VDEV_TYPE_HD:
> +if ((vdev->disk == 0 || vdev->disk == 1) &&
> +vdev->partition < (1 << 4)) {
I think that should be:
vdev->partition < (1 << 6)
Because hd disk have 0..63 partitions.
> +vdev->number = (3 << 8) | (vdev->disk << 6) | vdev->partition;
> +} else if ((vdev->disk == 2 || vdev->disk == 3) &&
> + vdev->partition < (1 << 4)) {
same here.
> +vdev->number = (22 << 8) | ((vdev->disk - 2) << 6) |
> +vdev->partition;
> +} else {
> +goto invalid;
> +}
> +break;
> +
> +case XEN_QDISK_VDEV_TYPE_SD:
> +if (vdev->disk < (1 << 4) && vdev->partition < (1 << 4)) {
> +vdev->number = (8 << 8) | (vdev->disk << 4) | vdev->partition;
> +} else {
> +goto invalid;
> +}
> +break;
> +
> +default:
> +goto invalid;
> +}
> +
> +g_free(str);
> +vdev->valid = true;
> +return;
> +
> +invalid:
> +error_setg(errp, "invalid virtual disk specifier");
> +g_free(str);
:(, g_free is called twice.
maybe we could have:
vdev->valid=true;
out:
if (!vdev->valid)
error_setg(...);
g_free;
> diff --git a/include/hw/xen/xen-qdisk.h b/include/hw/xen/xen-qdisk.h
> new file mode 100644
> index 00..ade0866037
> --- /dev/null
> +++ b/include/hw/xen/xen-qdisk.h
> @@ -0,0 +1,38 @@
> +/*
> + * Copyright (c) Citrix Systems Inc.
> + * All rights reserved.
> + */
> +
> +#ifndef HW_XEN_QDISK_H
> +#define HW_XEN_QDISK_H
> +
> +#include "hw/xen/xen-bus.h"
> +
> +typedef enum XenQdiskVdevType {
> +XEN_QDISK_VDEV_TYPE_DP,
Maybe we could set type_dp value to 1, so that, when vdev->type isn't
set, we can detect it later.
> +XEN_QDISK_VDEV_TYPE_XVD,
> +XEN_QDISK_VDEV_TYPE_HD,
> +XEN_QDISK_VDEV_TYPE_SD,
> +XEN_QDISK_VDEV_TYPE__MAX
> +} XenQdiskVdevType;
Thanks,
--
Anthony PERARD
[Qemu-block] [PATCH 03/18] xen: introduce 'xen-qdisk'
This patch adds a new XenDevice: 'xen-qdisk' [1]. This will eventually
replace the 'xen_disk' legacy PV backend but it is illustrative to build
up the implementation incrementally, along with the XenBus/XenDevice
framework. Subsequent patches will therefore add to this device's
implementation as new features are added to the framework.
After this patch has been applied it is possible to instantiate a new
'xen-qdisk' device with a single 'vdev' parameter, which accepts values
adhering to the Xen VBD naming scheme [2]. For example, a command-line
instantiation of a xen-qdisk can be done with an argument similar to the
following:
-device xen-qdisk,vdev=hda
The implementation of the vdev parameter formulates the appropriate VBD
number for use in the PV protocol.
[1] The name 'qdisk' as always been the name given to the QEMU
implementation of the Xen PV block protocol backend implementation
[2]
http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=docs/man/xen-vbd-interface.markdown.7
Signed-off-by: Paul Durrant
---
Cc: Kevin Wolf
Cc: Max Reitz
Cc: Stefano Stabellini
Cc: Anthony Perard
---
MAINTAINERS| 2 +-
hw/block/Makefile.objs | 1 +
hw/block/trace-events | 4 +
hw/block/xen-qdisk.c | 256 +
include/hw/xen/xen-qdisk.h | 38 +++
5 files changed, 300 insertions(+), 1 deletion(-)
create mode 100644 hw/block/xen-qdisk.c
create mode 100644 include/hw/xen/xen-qdisk.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 1032406c56..10f048a503 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -389,7 +389,7 @@ F: hw/9pfs/xen-9p-backend.c
F: hw/char/xen_console.c
F: hw/display/xenfb.c
F: hw/net/xen_nic.c
-F: hw/block/xen_*
+F: hw/block/xen*
F: hw/xen/
F: hw/xenpv/
F: hw/i386/xen/
diff --git a/hw/block/Makefile.objs b/hw/block/Makefile.objs
index 53ce5751ae..bcdd36d318 100644
--- a/hw/block/Makefile.objs
+++ b/hw/block/Makefile.objs
@@ -5,6 +5,7 @@ common-obj-$(CONFIG_NAND) += nand.o
common-obj-$(CONFIG_PFLASH_CFI01) += pflash_cfi01.o
common-obj-$(CONFIG_PFLASH_CFI02) += pflash_cfi02.o
common-obj-$(CONFIG_XEN) += xen_disk.o
+common-obj-$(CONFIG_XEN) += xen-qdisk.o
common-obj-$(CONFIG_ECC) += ecc.o
common-obj-$(CONFIG_ONENAND) += onenand.o
common-obj-$(CONFIG_NVME_PCI) += nvme.o
diff --git a/hw/block/trace-events b/hw/block/trace-events
index 335c092450..fd3c126ac1 100644
--- a/hw/block/trace-events
+++ b/hw/block/trace-events
@@ -127,3 +127,7 @@ xen_disk_init(char *name) "%s"
xen_disk_connect(char *name) "%s"
xen_disk_disconnect(char *name) "%s"
xen_disk_free(char *name) "%s"
+
+# hw/block/xen-qdisk.c
+xen_qdisk_realize(uint32_t disk, uint32_t partition) "d%up%u"
+xen_qdisk_unrealize(uint32_t disk, uint32_t partition) "d%up%u"
diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c
new file mode 100644
index 00..72122073f7
--- /dev/null
+++ b/hw/block/xen-qdisk.c
@@ -0,0 +1,256 @@
+/*
+ * Copyright (c) Citrix Systems Inc.
+ * All rights reserved.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/cutils.h"
+#include "qapi/error.h"
+#include "qapi/visitor.h"
+#include "hw/hw.h"
+#include "hw/xen/xen-qdisk.h"
+#include "trace.h"
+
+static void xen_qdisk_realize(XenDevice *xendev, Error **errp)
+{
+XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev);
+XenQdiskVdev *vdev = >vdev;
+
+if (!vdev->valid) {
+error_setg(errp, "vdev property not set");
+return;
+}
+
+trace_xen_qdisk_realize(vdev->disk, vdev->partition);
+}
+
+static void xen_qdisk_unrealize(XenDevice *xendev, Error **errp)
+{
+XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev);
+XenQdiskVdev *vdev = >vdev;
+
+trace_xen_qdisk_unrealize(vdev->disk, vdev->partition);
+}
+
+static char *disk_to_vbd_name(unsigned int disk)
+{
+unsigned int len = DIV_ROUND_UP(disk, 26);
+char *name = g_malloc0(len + 1);
+
+do {
+name[len--] = 'a' + (disk % 26);
+disk /= 26;
+} while (disk != 0);
+assert(len == 0);
+
+return name;
+}
+
+static void xen_qdisk_get_vdev(Object *obj, Visitor *v, const char *name,
+ void *opaque, Error **errp)
+{
+DeviceState *dev = DEVICE(obj);
+Property *prop = opaque;
+XenQdiskVdev *vdev = qdev_get_prop_ptr(dev, prop);
+char *str;
+
+switch (vdev->type) {
+case XEN_QDISK_VDEV_TYPE_DP:
+str = g_strdup_printf("d%lup%lu", vdev->disk, vdev->partition);
+break;
+
+case XEN_QDISK_VDEV_TYPE_XVD:
+case XEN_QDISK_VDEV_TYPE_HD:
+case XEN_QDISK_VDEV_TYPE_SD: {
+char *name = disk_to_vbd_name(vdev->disk);
+
+str = g_strdup_printf("%s%s%lu",
+ (vdev->type == XEN_QDISK_VDEV_TYPE_XVD) ?
+ "xvd" :
+ (vdev->type == XEN_QDISK_VDEV_TYPE_HD) ?
+ "hd" :
+ "sd",
+ name, vdev->partition);
+g_free(name);
+
