diff mbox

[v5,07/13] vfio/ccw: vfio based subchannel passthrough driver

Message ID 20170412052115.101657-8-bjsdjshi@linux.vnet.ibm.com (mailing list archive)
State New, archived
Headers show

Commit Message

Dong Jia Shi April 12, 2017, 5:21 a.m. UTC 
From: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>

We use the IOMMU_TYPE1 of VFIO to realize the subchannels
passthrough, implement a vfio based subchannels passthrough
driver called "vfio-ccw".

Support qemu parameters in the style of:
"-device vfio-ccw,sysfsdev=$mdev_file_path,devno=xx.x.xxxx'

Signed-off-by: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
---
 default-configs/s390x-softmmu.mak |   1 +
 hw/vfio/Makefile.objs             |   1 +
 hw/vfio/ccw.c                     | 207 ++++++++++++++++++++++++++++++++++++++
 include/hw/vfio/vfio-common.h     |   1 +
 4 files changed, 210 insertions(+)
 create mode 100644 hw/vfio/ccw.c

Comments

Alex Williamson April 24, 2017, 10:43 p.m. UTC | #1 
On Wed, 12 Apr 2017 07:21:09 +0200
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> From: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> 
> We use the IOMMU_TYPE1 of VFIO to realize the subchannels
> passthrough, implement a vfio based subchannels passthrough
> driver called "vfio-ccw".
> 
> Support qemu parameters in the style of:
> "-device vfio-ccw,sysfsdev=$mdev_file_path,devno=xx.x.xxxx'
> 
> Signed-off-by: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> ---
>  default-configs/s390x-softmmu.mak |   1 +
>  hw/vfio/Makefile.objs             |   1 +
>  hw/vfio/ccw.c                     | 207 ++++++++++++++++++++++++++++++++++++++
>  include/hw/vfio/vfio-common.h     |   1 +
>  4 files changed, 210 insertions(+)
>  create mode 100644 hw/vfio/ccw.c
> 
> diff --git a/default-configs/s390x-softmmu.mak b/default-configs/s390x-softmmu.mak
> index 36e15de..5576b0a 100644
> --- a/default-configs/s390x-softmmu.mak
> +++ b/default-configs/s390x-softmmu.mak
> @@ -4,4 +4,5 @@ CONFIG_VIRTIO=y
>  CONFIG_SCLPCONSOLE=y
>  CONFIG_S390_FLIC=y
>  CONFIG_S390_FLIC_KVM=$(CONFIG_KVM)
> +CONFIG_VFIO_CCW=$(CONFIG_LINUX)
>  CONFIG_WDT_DIAG288=y
> diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
> index 05e7fbb..c3ab909 100644
> --- a/hw/vfio/Makefile.objs
> +++ b/hw/vfio/Makefile.objs
> @@ -1,6 +1,7 @@
>  ifeq ($(CONFIG_LINUX), y)
>  obj-$(CONFIG_SOFTMMU) += common.o
>  obj-$(CONFIG_PCI) += pci.o pci-quirks.o
> +obj-$(CONFIG_VFIO_CCW) += ccw.o
>  obj-$(CONFIG_SOFTMMU) += platform.o
>  obj-$(CONFIG_VFIO_XGMAC) += calxeda-xgmac.o
>  obj-$(CONFIG_VFIO_AMD_XGBE) += amd-xgbe.o
> diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> new file mode 100644
> index 0000000..c491bee
> --- /dev/null
> +++ b/hw/vfio/ccw.c
> @@ -0,0 +1,207 @@
> +/*
> + * vfio based subchannel assignment support
> + *
> + * Copyright 2017 IBM Corp.
> + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> + *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> + *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or(at
> + * your option) any version. See the COPYING file in the top-level
> + * directory.
> + */
> +
> +#include <linux/vfio.h>
> +#include <sys/ioctl.h>
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "hw/sysbus.h"
> +#include "hw/vfio/vfio.h"
> +#include "hw/vfio/vfio-common.h"
> +#include "hw/s390x/s390-ccw.h"
> +#include "hw/s390x/ccw-device.h"
> +
> +#define TYPE_VFIO_CCW "vfio-ccw"
> +typedef struct VFIOCCWDevice {
> +    S390CCWDevice cdev;
> +    VFIODevice vdev;
> +} VFIOCCWDevice;
> +
> +static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> +{
> +    vdev->needs_reset = false;
> +}
> +
> +/*
> + * We don't need vfio_hot_reset_multi and vfio_eoi operationis for
> + * vfio_ccw device now.
> + */
> +struct VFIODeviceOps vfio_ccw_ops = {
> +    .vfio_compute_needs_reset = vfio_ccw_compute_needs_reset,
> +};
> +
> +static void vfio_ccw_reset(DeviceState *dev)
> +{
> +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> +
> +    ioctl(vcdev->vdev.fd, VFIO_DEVICE_RESET);
> +}
> +
> +static void vfio_put_device(VFIOCCWDevice *vcdev)
> +{
> +    g_free(vcdev->vdev.name);
> +    vfio_put_base_device(&vcdev->vdev);
> +}
> +
> +static VFIOGroup *vfio_ccw_get_group(S390CCWDevice *cdev, char **path,
> +                                     Error **errp)
> +{
> +    struct stat st;
> +    int groupid;
> +    GError *gerror = NULL;
> +
> +    /* Check that host subchannel exists. */
> +    path[0] = g_strdup_printf("/sys/bus/css/devices/%x.%x.%04x",
> +                              cdev->hostid.cssid,
> +                              cdev->hostid.ssid,
> +                              cdev->hostid.devid);
> +    if (stat(path[0], &st) < 0) {
> +        error_setg(errp, "vfio: no such host subchannel %s", path[0]);
> +        return NULL;
> +    }
> +
> +    /* Check that mediated device exists. */
> +    path[1] = g_strdup_printf("%s/%s", path[0], cdev->mdevid);
> +    if (stat(path[0], &st) < 0) {
> +        error_setg(errp, "vfio: no such mediated device %s", path[1]);
> +        return NULL;
> +    }

Isn't this all a bit circular since we build the S390CCWDevice based on
the sysfsdev mdev path?

> +
> +    /* Get the iommu_group patch as the interim variable. */
> +    path[2] = g_strconcat(path[1], "/iommu_group", NULL);
> +
> +    /* Get the link file path of the device iommu_group. */
> +    path[3] = g_file_read_link(path[2], &gerror);
> +    if (!path[3]) {
> +        error_setg(errp, "vfio: error no iommu_group for subchannel");
> +        return NULL;
> +    }
> +
> +    /* Get the device groupid. */
> +    if (sscanf(basename(path[3]), "%d", &groupid) != 1) {
> +        error_setg(errp, "vfio: error reading %s:%m", path[3]);
> +        return NULL;
> +    }
> +
> +    return vfio_get_group(groupid, &address_space_memory, errp);
> +}
> +
> +static void vfio_ccw_put_group(VFIOGroup *group, char **path)
> +{
> +    g_free(path);
> +    vfio_put_group(group);
> +}
> +
> +static void vfio_ccw_realize(DeviceState *dev, Error **errp)
> +{
> +    VFIODevice *vbasedev;
> +    VFIOGroup *group;
> +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> +    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
> +    char *path[4] = {NULL, NULL, NULL, NULL};

I don't understand what's happening with 'path' throughout this
function.  vfio_ccw_get_group() allocates strings into this array, we
only seem to use one in an error path below, it's only freed on an error
path and I don't see it getting linked to the VFIOCCWDevice, so it
seems to be leaked, and even the g_free() above looks quite a bit
suspicious.

> +
> +    /* Call the class init function for subchannel. */
> +    if (cdc->realize) {
> +        cdc->realize(cdev, vcdev->vdev.sysfsdev, errp);
> +        if (*errp) {
> +            return;
> +        }
> +    }
> +
> +    group = vfio_ccw_get_group(cdev, path, errp);
> +    if (!group) {
> +        goto out_group_err;
> +    }
> +
> +    vcdev->vdev.ops = &vfio_ccw_ops;
> +    vcdev->vdev.type = VFIO_DEVICE_TYPE_CCW;
> +    vcdev->vdev.name = g_strdup_printf("%x.%x.%04x", cdev->hostid.cssid,
> +                                       cdev->hostid.ssid, cdev->hostid.devid);
> +    QLIST_FOREACH(vbasedev, &group->device_list, next) {
> +        if (strcmp(vbasedev->name, vcdev->vdev.name) == 0) {
> +            error_setg(errp, "vfio: subchannel %s has already been attached",
> +                       basename(path[0]));
> +            goto out_device_err;
> +        }
> +    }
> +
> +    if (vfio_get_device(group, cdev->mdevid, &vcdev->vdev, errp)) {
> +        goto out_device_err;
> +    }
> +
> +    return;
> +
> +out_device_err:
> +    vfio_ccw_put_group(group, path);
> +out_group_err:
> +    if (cdc->unrealize) {
> +        cdc->unrealize(cdev, errp);
> +    }
> +}
> +
> +static void vfio_ccw_unrealize(DeviceState *dev, Error **errp)
> +{
> +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> +    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
> +    VFIOGroup *group = vcdev->vdev.group;
> +
> +    if (cdc->unrealize) {
> +        cdc->unrealize(cdev, errp);
> +    }
> +
> +    vfio_put_device(vcdev);
> +    vfio_put_group(group);
> +}

Doesn't seem to matter here, but I would have expected the
cdc->unrealize to occur at the end to unwind the order of the realize
function.

> +
> +static Property vfio_ccw_properties[] = {
> +    DEFINE_PROP_STRING("sysfsdev", VFIOCCWDevice, vdev.sysfsdev),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static const VMStateDescription vfio_ccw_vmstate = {
> +    .name = TYPE_VFIO_CCW,
> +    .unmigratable = 1,
> +};
> +
> +static void vfio_ccw_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->props = vfio_ccw_properties;
> +    dc->vmsd = &vfio_ccw_vmstate;
> +    dc->desc = "VFIO-based subchannel assignment";
> +    dc->realize = vfio_ccw_realize;
> +    dc->unrealize = vfio_ccw_unrealize;
> +    dc->reset = vfio_ccw_reset;
> +}
> +
> +static const TypeInfo vfio_ccw_info = {
> +    .name = TYPE_VFIO_CCW,
> +    .parent = TYPE_S390_CCW,
> +    .instance_size = sizeof(VFIOCCWDevice),
> +    .class_init = vfio_ccw_class_init,
> +};
> +
> +static void register_vfio_ccw_type(void)
> +{
> +    type_register_static(&vfio_ccw_info);
> +}
> +
> +type_init(register_vfio_ccw_type)
> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> index c582de1..9521013 100644
> --- a/include/hw/vfio/vfio-common.h
> +++ b/include/hw/vfio/vfio-common.h
> @@ -45,6 +45,7 @@
>  enum {
>      VFIO_DEVICE_TYPE_PCI = 0,
>      VFIO_DEVICE_TYPE_PLATFORM = 1,
> +    VFIO_DEVICE_TYPE_CCW = 2,
>  };
>  
>  typedef struct VFIOMmap {
Alex Williamson April 24, 2017, 10:56 p.m. UTC | #2 
On Mon, 24 Apr 2017 16:43:38 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> On Wed, 12 Apr 2017 07:21:09 +0200
> Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
> 
> > From: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > 
> > We use the IOMMU_TYPE1 of VFIO to realize the subchannels
> > passthrough, implement a vfio based subchannels passthrough
> > driver called "vfio-ccw".
> > 
> > Support qemu parameters in the style of:
> > "-device vfio-ccw,sysfsdev=$mdev_file_path,devno=xx.x.xxxx'
> > 
> > Signed-off-by: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > ---
> >  default-configs/s390x-softmmu.mak |   1 +
> >  hw/vfio/Makefile.objs             |   1 +
> >  hw/vfio/ccw.c                     | 207 ++++++++++++++++++++++++++++++++++++++
> >  include/hw/vfio/vfio-common.h     |   1 +
> >  4 files changed, 210 insertions(+)
> >  create mode 100644 hw/vfio/ccw.c
> > 
> > diff --git a/default-configs/s390x-softmmu.mak b/default-configs/s390x-softmmu.mak
> > index 36e15de..5576b0a 100644
> > --- a/default-configs/s390x-softmmu.mak
> > +++ b/default-configs/s390x-softmmu.mak
> > @@ -4,4 +4,5 @@ CONFIG_VIRTIO=y
> >  CONFIG_SCLPCONSOLE=y
> >  CONFIG_S390_FLIC=y
> >  CONFIG_S390_FLIC_KVM=$(CONFIG_KVM)
> > +CONFIG_VFIO_CCW=$(CONFIG_LINUX)
> >  CONFIG_WDT_DIAG288=y
> > diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
> > index 05e7fbb..c3ab909 100644
> > --- a/hw/vfio/Makefile.objs
> > +++ b/hw/vfio/Makefile.objs
> > @@ -1,6 +1,7 @@
> >  ifeq ($(CONFIG_LINUX), y)
> >  obj-$(CONFIG_SOFTMMU) += common.o
> >  obj-$(CONFIG_PCI) += pci.o pci-quirks.o
> > +obj-$(CONFIG_VFIO_CCW) += ccw.o
> >  obj-$(CONFIG_SOFTMMU) += platform.o
> >  obj-$(CONFIG_VFIO_XGMAC) += calxeda-xgmac.o
> >  obj-$(CONFIG_VFIO_AMD_XGBE) += amd-xgbe.o
> > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > new file mode 100644
> > index 0000000..c491bee
> > --- /dev/null
> > +++ b/hw/vfio/ccw.c
> > @@ -0,0 +1,207 @@
> > +/*
> > + * vfio based subchannel assignment support
> > + *
> > + * Copyright 2017 IBM Corp.
> > + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > + *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > + *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2 or(at
> > + * your option) any version. See the COPYING file in the top-level
> > + * directory.
> > + */
> > +
> > +#include <linux/vfio.h>
> > +#include <sys/ioctl.h>
> > +
> > +#include "qemu/osdep.h"
> > +#include "qapi/error.h"
> > +#include "hw/sysbus.h"
> > +#include "hw/vfio/vfio.h"
> > +#include "hw/vfio/vfio-common.h"
> > +#include "hw/s390x/s390-ccw.h"
> > +#include "hw/s390x/ccw-device.h"
> > +
> > +#define TYPE_VFIO_CCW "vfio-ccw"
> > +typedef struct VFIOCCWDevice {
> > +    S390CCWDevice cdev;
> > +    VFIODevice vdev;
> > +} VFIOCCWDevice;
> > +
> > +static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> > +{
> > +    vdev->needs_reset = false;
> > +}
> > +
> > +/*
> > + * We don't need vfio_hot_reset_multi and vfio_eoi operationis for

One more:

s/operationis/operations/

> > + * vfio_ccw device now.
> > + */
> > +struct VFIODeviceOps vfio_ccw_ops = {
> > +    .vfio_compute_needs_reset = vfio_ccw_compute_needs_reset,
> > +};
> > +
> > +static void vfio_ccw_reset(DeviceState *dev)
> > +{
> > +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> > +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> > +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> > +
> > +    ioctl(vcdev->vdev.fd, VFIO_DEVICE_RESET);
> > +}
> > +
> > +static void vfio_put_device(VFIOCCWDevice *vcdev)
> > +{
> > +    g_free(vcdev->vdev.name);
> > +    vfio_put_base_device(&vcdev->vdev);
> > +}
> > +
> > +static VFIOGroup *vfio_ccw_get_group(S390CCWDevice *cdev, char **path,
> > +                                     Error **errp)
> > +{
> > +    struct stat st;
> > +    int groupid;
> > +    GError *gerror = NULL;
> > +
> > +    /* Check that host subchannel exists. */
> > +    path[0] = g_strdup_printf("/sys/bus/css/devices/%x.%x.%04x",
> > +                              cdev->hostid.cssid,
> > +                              cdev->hostid.ssid,
> > +                              cdev->hostid.devid);
> > +    if (stat(path[0], &st) < 0) {
> > +        error_setg(errp, "vfio: no such host subchannel %s", path[0]);
> > +        return NULL;
> > +    }
> > +
> > +    /* Check that mediated device exists. */
> > +    path[1] = g_strdup_printf("%s/%s", path[0], cdev->mdevid);
> > +    if (stat(path[0], &st) < 0) {
> > +        error_setg(errp, "vfio: no such mediated device %s", path[1]);
> > +        return NULL;
> > +    }  
> 
> Isn't this all a bit circular since we build the S390CCWDevice based on
> the sysfsdev mdev path?
> 
> > +
> > +    /* Get the iommu_group patch as the interim variable. */
> > +    path[2] = g_strconcat(path[1], "/iommu_group", NULL);
> > +
> > +    /* Get the link file path of the device iommu_group. */
> > +    path[3] = g_file_read_link(path[2], &gerror);
> > +    if (!path[3]) {
> > +        error_setg(errp, "vfio: error no iommu_group for subchannel");
> > +        return NULL;
> > +    }
> > +
> > +    /* Get the device groupid. */
> > +    if (sscanf(basename(path[3]), "%d", &groupid) != 1) {
> > +        error_setg(errp, "vfio: error reading %s:%m", path[3]);
> > +        return NULL;
> > +    }
> > +
> > +    return vfio_get_group(groupid, &address_space_memory, errp);
> > +}
> > +
> > +static void vfio_ccw_put_group(VFIOGroup *group, char **path)
> > +{
> > +    g_free(path);
> > +    vfio_put_group(group);
> > +}
> > +
> > +static void vfio_ccw_realize(DeviceState *dev, Error **errp)
> > +{
> > +    VFIODevice *vbasedev;
> > +    VFIOGroup *group;
> > +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> > +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> > +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> > +    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
> > +    char *path[4] = {NULL, NULL, NULL, NULL};  
> 
> I don't understand what's happening with 'path' throughout this
> function.  vfio_ccw_get_group() allocates strings into this array, we
> only seem to use one in an error path below, it's only freed on an error
> path and I don't see it getting linked to the VFIOCCWDevice, so it
> seems to be leaked, and even the g_free() above looks quite a bit
> suspicious.
> 
> > +
> > +    /* Call the class init function for subchannel. */
> > +    if (cdc->realize) {
> > +        cdc->realize(cdev, vcdev->vdev.sysfsdev, errp);
> > +        if (*errp) {
> > +            return;
> > +        }
> > +    }
> > +
> > +    group = vfio_ccw_get_group(cdev, path, errp);
> > +    if (!group) {
> > +        goto out_group_err;
> > +    }
> > +
> > +    vcdev->vdev.ops = &vfio_ccw_ops;
> > +    vcdev->vdev.type = VFIO_DEVICE_TYPE_CCW;
> > +    vcdev->vdev.name = g_strdup_printf("%x.%x.%04x", cdev->hostid.cssid,
> > +                                       cdev->hostid.ssid, cdev->hostid.devid);
> > +    QLIST_FOREACH(vbasedev, &group->device_list, next) {
> > +        if (strcmp(vbasedev->name, vcdev->vdev.name) == 0) {
> > +            error_setg(errp, "vfio: subchannel %s has already been attached",
> > +                       basename(path[0]));
> > +            goto out_device_err;
> > +        }
> > +    }
> > +
> > +    if (vfio_get_device(group, cdev->mdevid, &vcdev->vdev, errp)) {
> > +        goto out_device_err;
> > +    }
> > +
> > +    return;
> > +
> > +out_device_err:
> > +    vfio_ccw_put_group(group, path);
> > +out_group_err:
> > +    if (cdc->unrealize) {
> > +        cdc->unrealize(cdev, errp);
> > +    }
> > +}
> > +
> > +static void vfio_ccw_unrealize(DeviceState *dev, Error **errp)
> > +{
> > +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> > +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> > +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> > +    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
> > +    VFIOGroup *group = vcdev->vdev.group;
> > +
> > +    if (cdc->unrealize) {
> > +        cdc->unrealize(cdev, errp);
> > +    }
> > +
> > +    vfio_put_device(vcdev);
> > +    vfio_put_group(group);
> > +}  
> 
> Doesn't seem to matter here, but I would have expected the
> cdc->unrealize to occur at the end to unwind the order of the realize
> function.
> 
> > +
> > +static Property vfio_ccw_properties[] = {
> > +    DEFINE_PROP_STRING("sysfsdev", VFIOCCWDevice, vdev.sysfsdev),
> > +    DEFINE_PROP_END_OF_LIST(),
> > +};
> > +
> > +static const VMStateDescription vfio_ccw_vmstate = {
> > +    .name = TYPE_VFIO_CCW,
> > +    .unmigratable = 1,
> > +};
> > +
> > +static void vfio_ccw_class_init(ObjectClass *klass, void *data)
> > +{
> > +    DeviceClass *dc = DEVICE_CLASS(klass);
> > +
> > +    dc->props = vfio_ccw_properties;
> > +    dc->vmsd = &vfio_ccw_vmstate;
> > +    dc->desc = "VFIO-based subchannel assignment";
> > +    dc->realize = vfio_ccw_realize;
> > +    dc->unrealize = vfio_ccw_unrealize;
> > +    dc->reset = vfio_ccw_reset;
> > +}
> > +
> > +static const TypeInfo vfio_ccw_info = {
> > +    .name = TYPE_VFIO_CCW,
> > +    .parent = TYPE_S390_CCW,
> > +    .instance_size = sizeof(VFIOCCWDevice),
> > +    .class_init = vfio_ccw_class_init,
> > +};
> > +
> > +static void register_vfio_ccw_type(void)
> > +{
> > +    type_register_static(&vfio_ccw_info);
> > +}
> > +
> > +type_init(register_vfio_ccw_type)
> > diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
> > index c582de1..9521013 100644
> > --- a/include/hw/vfio/vfio-common.h
> > +++ b/include/hw/vfio/vfio-common.h
> > @@ -45,6 +45,7 @@
> >  enum {
> >      VFIO_DEVICE_TYPE_PCI = 0,
> >      VFIO_DEVICE_TYPE_PLATFORM = 1,
> > +    VFIO_DEVICE_TYPE_CCW = 2,
> >  };
> >  
> >  typedef struct VFIOMmap {  
>
Dong Jia Shi April 25, 2017, 5:15 a.m. UTC | #3 
* Alex Williamson <alex.williamson@redhat.com> [2017-04-24 16:56:28 -0600]:

[...]
> > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > new file mode 100644
> > > index 0000000..c491bee
> > > --- /dev/null
> > > +++ b/hw/vfio/ccw.c
> > > @@ -0,0 +1,207 @@
> > > +/*
> > > + * vfio based subchannel assignment support
> > > + *
> > > + * Copyright 2017 IBM Corp.
> > > + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > > + *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > > + *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> > > + *
> > > + * This work is licensed under the terms of the GNU GPL, version 2 or(at
> > > + * your option) any version. See the COPYING file in the top-level
> > > + * directory.
> > > + */
> > > +
> > > +#include <linux/vfio.h>
> > > +#include <sys/ioctl.h>
> > > +
> > > +#include "qemu/osdep.h"
> > > +#include "qapi/error.h"
> > > +#include "hw/sysbus.h"
> > > +#include "hw/vfio/vfio.h"
> > > +#include "hw/vfio/vfio-common.h"
> > > +#include "hw/s390x/s390-ccw.h"
> > > +#include "hw/s390x/ccw-device.h"
> > > +
> > > +#define TYPE_VFIO_CCW "vfio-ccw"
> > > +typedef struct VFIOCCWDevice {
> > > +    S390CCWDevice cdev;
> > > +    VFIODevice vdev;
> > > +} VFIOCCWDevice;
> > > +
> > > +static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> > > +{
> > > +    vdev->needs_reset = false;
> > > +}
> > > +
> > > +/*
> > > + * We don't need vfio_hot_reset_multi and vfio_eoi operationis for
> 
> One more:
> 
> s/operationis/operations/
> 
Ok.

> > > + * vfio_ccw device now.
> > > + */
> > > +struct VFIODeviceOps vfio_ccw_ops = {
> > > +    .vfio_compute_needs_reset = vfio_ccw_compute_needs_reset,
> > > +};
> > > +
> > > +static void vfio_ccw_reset(DeviceState *dev)
> > > +{
> > > +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> > > +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> > > +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> > > +
> > > +    ioctl(vcdev->vdev.fd, VFIO_DEVICE_RESET);
> > > +}
> > > +
> > > +static void vfio_put_device(VFIOCCWDevice *vcdev)
> > > +{
> > > +    g_free(vcdev->vdev.name);
> > > +    vfio_put_base_device(&vcdev->vdev);
> > > +}
> > > +
> > > +static VFIOGroup *vfio_ccw_get_group(S390CCWDevice *cdev, char **path,
> > > +                                     Error **errp)
> > > +{
> > > +    struct stat st;
> > > +    int groupid;
> > > +    GError *gerror = NULL;
> > > +
> > > +    /* Check that host subchannel exists. */
> > > +    path[0] = g_strdup_printf("/sys/bus/css/devices/%x.%x.%04x",
> > > +                              cdev->hostid.cssid,
> > > +                              cdev->hostid.ssid,
> > > +                              cdev->hostid.devid);
> > > +    if (stat(path[0], &st) < 0) {
> > > +        error_setg(errp, "vfio: no such host subchannel %s", path[0]);
> > > +        return NULL;
> > > +    }
> > > +
> > > +    /* Check that mediated device exists. */
> > > +    path[1] = g_strdup_printf("%s/%s", path[0], cdev->mdevid);
> > > +    if (stat(path[0], &st) < 0) {
> > > +        error_setg(errp, "vfio: no such mediated device %s", path[1]);
> > > +        return NULL;
> > > +    }  
> > 
> > Isn't this all a bit circular since we build the S390CCWDevice based on
> > the sysfsdev mdev path?
> > 
Right! We don't need to verify the existance of the path here again,
since we already did that during the realization of the S390CCWDevice,
which is triggered by calling cdc->realize before vfio_ccw_get_group in
vfio_ccw_realize.

> > > +
> > > +    /* Get the iommu_group patch as the interim variable. */
> > > +    path[2] = g_strconcat(path[1], "/iommu_group", NULL);
> > > +
> > > +    /* Get the link file path of the device iommu_group. */
> > > +    path[3] = g_file_read_link(path[2], &gerror);
> > > +    if (!path[3]) {
> > > +        error_setg(errp, "vfio: error no iommu_group for subchannel");
> > > +        return NULL;
> > > +    }
> > > +
> > > +    /* Get the device groupid. */
> > > +    if (sscanf(basename(path[3]), "%d", &groupid) != 1) {
> > > +        error_setg(errp, "vfio: error reading %s:%m", path[3]);
> > > +        return NULL;
> > > +    }
> > > +
> > > +    return vfio_get_group(groupid, &address_space_memory, errp);
> > > +}
> > > +
> > > +static void vfio_ccw_put_group(VFIOGroup *group, char **path)
> > > +{
> > > +    g_free(path);
> > > +    vfio_put_group(group);
> > > +}
> > > +
> > > +static void vfio_ccw_realize(DeviceState *dev, Error **errp)
> > > +{
> > > +    VFIODevice *vbasedev;
> > > +    VFIOGroup *group;
> > > +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> > > +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> > > +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> > > +    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
> > > +    char *path[4] = {NULL, NULL, NULL, NULL};  
> > 
> > I don't understand what's happening with 'path' throughout this
> > function.  vfio_ccw_get_group() allocates strings into this array, we
> > only seem to use one in an error path below, it's only freed on an error
> > path and I don't see it getting linked to the VFIOCCWDevice, so it
> > seems to be leaked, and even the g_free() above looks quite a bit
> > suspicious.
This @path, together with the operations on it, must be a leftover of a
previous implementation. I will rewrite these stuff. Thanks for the
catch!

> > 
> > > +
> > > +    /* Call the class init function for subchannel. */
> > > +    if (cdc->realize) {
> > > +        cdc->realize(cdev, vcdev->vdev.sysfsdev, errp);
> > > +        if (*errp) {
> > > +            return;
> > > +        }
> > > +    }
> > > +
> > > +    group = vfio_ccw_get_group(cdev, path, errp);
> > > +    if (!group) {
> > > +        goto out_group_err;
> > > +    }
> > > +
> > > +    vcdev->vdev.ops = &vfio_ccw_ops;
> > > +    vcdev->vdev.type = VFIO_DEVICE_TYPE_CCW;
> > > +    vcdev->vdev.name = g_strdup_printf("%x.%x.%04x", cdev->hostid.cssid,
> > > +                                       cdev->hostid.ssid, cdev->hostid.devid);
> > > +    QLIST_FOREACH(vbasedev, &group->device_list, next) {
> > > +        if (strcmp(vbasedev->name, vcdev->vdev.name) == 0) {
> > > +            error_setg(errp, "vfio: subchannel %s has already been attached",
> > > +                       basename(path[0]));
> > > +            goto out_device_err;
> > > +        }
> > > +    }
> > > +
> > > +    if (vfio_get_device(group, cdev->mdevid, &vcdev->vdev, errp)) {
> > > +        goto out_device_err;
> > > +    }
> > > +
> > > +    return;
> > > +
> > > +out_device_err:
> > > +    vfio_ccw_put_group(group, path);
> > > +out_group_err:
> > > +    if (cdc->unrealize) {
> > > +        cdc->unrealize(cdev, errp);
> > > +    }
> > > +}
> > > +
> > > +static void vfio_ccw_unrealize(DeviceState *dev, Error **errp)
> > > +{
> > > +    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
> > > +    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
> > > +    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
> > > +    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
> > > +    VFIOGroup *group = vcdev->vdev.group;
> > > +
> > > +    if (cdc->unrealize) {
> > > +        cdc->unrealize(cdev, errp);
> > > +    }
> > > +
> > > +    vfio_put_device(vcdev);
> > > +    vfio_put_group(group);
> > > +}  
> > 
> > Doesn't seem to matter here, but I would have expected the
> > cdc->unrealize to occur at the end to unwind the order of the realize
> > function.
Ok! Will do.

> > 
> > > +
[...]
Dong Jia Shi April 26, 2017, 8:49 a.m. UTC | #4 
* Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> [2017-04-25 13:15:19 +0800]:

> * Alex Williamson <alex.williamson@redhat.com> [2017-04-24 16:56:28 -0600]:
> 
> [...]
> > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > > new file mode 100644
> > > > index 0000000..c491bee
> > > > --- /dev/null
> > > > +++ b/hw/vfio/ccw.c
> > > > @@ -0,0 +1,207 @@
> > > > +/*
> > > > + * vfio based subchannel assignment support
> > > > + *
> > > > + * Copyright 2017 IBM Corp.
> > > > + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > > > + *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > > > + *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> > > > + *
> > > > + * This work is licensed under the terms of the GNU GPL, version 2 or(at
> > > > + * your option) any version. See the COPYING file in the top-level
> > > > + * directory.
> > > > + */
> > > > +
> > > > +#include <linux/vfio.h>
> > > > +#include <sys/ioctl.h>
> > > > +
> > > > +#include "qemu/osdep.h"
> > > > +#include "qapi/error.h"
> > > > +#include "hw/sysbus.h"
> > > > +#include "hw/vfio/vfio.h"
> > > > +#include "hw/vfio/vfio-common.h"
> > > > +#include "hw/s390x/s390-ccw.h"
> > > > +#include "hw/s390x/ccw-device.h"
> > > > +
> > > > +#define TYPE_VFIO_CCW "vfio-ccw"
> > > > +typedef struct VFIOCCWDevice {
> > > > +    S390CCWDevice cdev;
> > > > +    VFIODevice vdev;
> > > > +} VFIOCCWDevice;
> > > > +
> > > > +static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> > > > +{
> > > > +    vdev->needs_reset = false;
> > > > +}
> > > > +
> > > > +/*
> > > > + * We don't need vfio_hot_reset_multi and vfio_eoi operationis for
> > 
> > One more:
> > 
> > s/operationis/operations/
> > 
> Ok.
> 

Hi Conny,

I have pulled your cohuck-qemu/s390-next branch, and prepared a new
patch set with all of these problems fixed directly on the coressponding
commits on it. Fine to send out the new version as that?

Or I should rebase them against the latest master branch?

Thanks.

[...]
Cornelia Huck April 28, 2017, 11:04 a.m. UTC | #5 
On Wed, 26 Apr 2017 16:49:20 +0800
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> * Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> [2017-04-25 13:15:19 +0800]:
> 
> > * Alex Williamson <alex.williamson@redhat.com> [2017-04-24 16:56:28 -0600]:
> > 
> > [...]
> > > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > > > new file mode 100644
> > > > > index 0000000..c491bee
> > > > > --- /dev/null
> > > > > +++ b/hw/vfio/ccw.c
> > > > > @@ -0,0 +1,207 @@
> > > > > +/*
> > > > > + * vfio based subchannel assignment support
> > > > > + *
> > > > > + * Copyright 2017 IBM Corp.
> > > > > + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > > > > + *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > > > > + *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> > > > > + *
> > > > > + * This work is licensed under the terms of the GNU GPL, version 2 or(at
> > > > > + * your option) any version. See the COPYING file in the top-level
> > > > > + * directory.
> > > > > + */
> > > > > +
> > > > > +#include <linux/vfio.h>
> > > > > +#include <sys/ioctl.h>
> > > > > +
> > > > > +#include "qemu/osdep.h"
> > > > > +#include "qapi/error.h"
> > > > > +#include "hw/sysbus.h"
> > > > > +#include "hw/vfio/vfio.h"
> > > > > +#include "hw/vfio/vfio-common.h"
> > > > > +#include "hw/s390x/s390-ccw.h"
> > > > > +#include "hw/s390x/ccw-device.h"
> > > > > +
> > > > > +#define TYPE_VFIO_CCW "vfio-ccw"
> > > > > +typedef struct VFIOCCWDevice {
> > > > > +    S390CCWDevice cdev;
> > > > > +    VFIODevice vdev;
> > > > > +} VFIOCCWDevice;
> > > > > +
> > > > > +static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> > > > > +{
> > > > > +    vdev->needs_reset = false;
> > > > > +}
> > > > > +
> > > > > +/*
> > > > > + * We don't need vfio_hot_reset_multi and vfio_eoi operationis for
> > > 
> > > One more:
> > > 
> > > s/operationis/operations/
> > > 
> > Ok.
> > 
> 
> Hi Conny,
> 
> I have pulled your cohuck-qemu/s390-next branch, and prepared a new
> patch set with all of these problems fixed directly on the coressponding
> commits on it. Fine to send out the new version as that?
> 
> Or I should rebase them against the latest master branch?

As I currently don't have things in my next branch that should interact
with your changes, either is fine :)

[I'll take a look at the new version then]
Dong Jia Shi April 28, 2017, 1:12 p.m. UTC | #6 
* Cornelia Huck <cornelia.huck@de.ibm.com> [2017-04-28 13:04:07 +0200]:

> On Wed, 26 Apr 2017 16:49:20 +0800
> Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:
> 
> > * Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> [2017-04-25 13:15:19 +0800]:
> > 
> > > * Alex Williamson <alex.williamson@redhat.com> [2017-04-24 16:56:28 -0600]:
> > > 
> > > [...]
> > > > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > > > > new file mode 100644
> > > > > > index 0000000..c491bee
> > > > > > --- /dev/null
> > > > > > +++ b/hw/vfio/ccw.c
> > > > > > @@ -0,0 +1,207 @@
> > > > > > +/*
> > > > > > + * vfio based subchannel assignment support
> > > > > > + *
> > > > > > + * Copyright 2017 IBM Corp.
> > > > > > + * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
> > > > > > + *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> > > > > > + *            Pierre Morel <pmorel@linux.vnet.ibm.com>
> > > > > > + *
> > > > > > + * This work is licensed under the terms of the GNU GPL, version 2 or(at
> > > > > > + * your option) any version. See the COPYING file in the top-level
> > > > > > + * directory.
> > > > > > + */
> > > > > > +
> > > > > > +#include <linux/vfio.h>
> > > > > > +#include <sys/ioctl.h>
> > > > > > +
> > > > > > +#include "qemu/osdep.h"
> > > > > > +#include "qapi/error.h"
> > > > > > +#include "hw/sysbus.h"
> > > > > > +#include "hw/vfio/vfio.h"
> > > > > > +#include "hw/vfio/vfio-common.h"
> > > > > > +#include "hw/s390x/s390-ccw.h"
> > > > > > +#include "hw/s390x/ccw-device.h"
> > > > > > +
> > > > > > +#define TYPE_VFIO_CCW "vfio-ccw"
> > > > > > +typedef struct VFIOCCWDevice {
> > > > > > +    S390CCWDevice cdev;
> > > > > > +    VFIODevice vdev;
> > > > > > +} VFIOCCWDevice;
> > > > > > +
> > > > > > +static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> > > > > > +{
> > > > > > +    vdev->needs_reset = false;
> > > > > > +}
> > > > > > +
> > > > > > +/*
> > > > > > + * We don't need vfio_hot_reset_multi and vfio_eoi operationis for
> > > > 
> > > > One more:
> > > > 
> > > > s/operationis/operations/
> > > > 
> > > Ok.
> > > 
> > 
> > Hi Conny,
> > 
> > I have pulled your cohuck-qemu/s390-next branch, and prepared a new
> > patch set with all of these problems fixed directly on the coressponding
> > commits on it. Fine to send out the new version as that?
> > 
> > Or I should rebase them against the latest master branch?
> 
> As I currently don't have things in my next branch that should interact
> with your changes, either is fine :)
Thanks! :>
I used your branch as the code base and just sent out the v6 patches.

> 
> [I'll take a look at the new version then]
diff mbox

Patch

diff --git a/default-configs/s390x-softmmu.mak b/default-configs/s390x-softmmu.mak
index 36e15de..5576b0a 100644
--- a/default-configs/s390x-softmmu.mak
+++ b/default-configs/s390x-softmmu.mak
@@ -4,4 +4,5 @@  CONFIG_VIRTIO=y
 CONFIG_SCLPCONSOLE=y
 CONFIG_S390_FLIC=y
 CONFIG_S390_FLIC_KVM=$(CONFIG_KVM)
+CONFIG_VFIO_CCW=$(CONFIG_LINUX)
 CONFIG_WDT_DIAG288=y
diff --git a/hw/vfio/Makefile.objs b/hw/vfio/Makefile.objs
index 05e7fbb..c3ab909 100644
--- a/hw/vfio/Makefile.objs
+++ b/hw/vfio/Makefile.objs
@@ -1,6 +1,7 @@ 
 ifeq ($(CONFIG_LINUX), y)
 obj-$(CONFIG_SOFTMMU) += common.o
 obj-$(CONFIG_PCI) += pci.o pci-quirks.o
+obj-$(CONFIG_VFIO_CCW) += ccw.o
 obj-$(CONFIG_SOFTMMU) += platform.o
 obj-$(CONFIG_VFIO_XGMAC) += calxeda-xgmac.o
 obj-$(CONFIG_VFIO_AMD_XGBE) += amd-xgbe.o
diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
new file mode 100644
index 0000000..c491bee
--- /dev/null
+++ b/hw/vfio/ccw.c
@@ -0,0 +1,207 @@ 
+/*
+ * vfio based subchannel assignment support
+ *
+ * Copyright 2017 IBM Corp.
+ * Author(s): Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
+ *            Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
+ *            Pierre Morel <pmorel@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or(at
+ * your option) any version. See the COPYING file in the top-level
+ * directory.
+ */
+
+#include <linux/vfio.h>
+#include <sys/ioctl.h>
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "hw/sysbus.h"
+#include "hw/vfio/vfio.h"
+#include "hw/vfio/vfio-common.h"
+#include "hw/s390x/s390-ccw.h"
+#include "hw/s390x/ccw-device.h"
+
+#define TYPE_VFIO_CCW "vfio-ccw"
+typedef struct VFIOCCWDevice {
+    S390CCWDevice cdev;
+    VFIODevice vdev;
+} VFIOCCWDevice;
+
+static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
+{
+    vdev->needs_reset = false;
+}
+
+/*
+ * We don't need vfio_hot_reset_multi and vfio_eoi operationis for
+ * vfio_ccw device now.
+ */
+struct VFIODeviceOps vfio_ccw_ops = {
+    .vfio_compute_needs_reset = vfio_ccw_compute_needs_reset,
+};
+
+static void vfio_ccw_reset(DeviceState *dev)
+{
+    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
+    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
+    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
+
+    ioctl(vcdev->vdev.fd, VFIO_DEVICE_RESET);
+}
+
+static void vfio_put_device(VFIOCCWDevice *vcdev)
+{
+    g_free(vcdev->vdev.name);
+    vfio_put_base_device(&vcdev->vdev);
+}
+
+static VFIOGroup *vfio_ccw_get_group(S390CCWDevice *cdev, char **path,
+                                     Error **errp)
+{
+    struct stat st;
+    int groupid;
+    GError *gerror = NULL;
+
+    /* Check that host subchannel exists. */
+    path[0] = g_strdup_printf("/sys/bus/css/devices/%x.%x.%04x",
+                              cdev->hostid.cssid,
+                              cdev->hostid.ssid,
+                              cdev->hostid.devid);
+    if (stat(path[0], &st) < 0) {
+        error_setg(errp, "vfio: no such host subchannel %s", path[0]);
+        return NULL;
+    }
+
+    /* Check that mediated device exists. */
+    path[1] = g_strdup_printf("%s/%s", path[0], cdev->mdevid);
+    if (stat(path[0], &st) < 0) {
+        error_setg(errp, "vfio: no such mediated device %s", path[1]);
+        return NULL;
+    }
+
+    /* Get the iommu_group patch as the interim variable. */
+    path[2] = g_strconcat(path[1], "/iommu_group", NULL);
+
+    /* Get the link file path of the device iommu_group. */
+    path[3] = g_file_read_link(path[2], &gerror);
+    if (!path[3]) {
+        error_setg(errp, "vfio: error no iommu_group for subchannel");
+        return NULL;
+    }
+
+    /* Get the device groupid. */
+    if (sscanf(basename(path[3]), "%d", &groupid) != 1) {
+        error_setg(errp, "vfio: error reading %s:%m", path[3]);
+        return NULL;
+    }
+
+    return vfio_get_group(groupid, &address_space_memory, errp);
+}
+
+static void vfio_ccw_put_group(VFIOGroup *group, char **path)
+{
+    g_free(path);
+    vfio_put_group(group);
+}
+
+static void vfio_ccw_realize(DeviceState *dev, Error **errp)
+{
+    VFIODevice *vbasedev;
+    VFIOGroup *group;
+    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
+    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
+    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
+    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
+    char *path[4] = {NULL, NULL, NULL, NULL};
+
+    /* Call the class init function for subchannel. */
+    if (cdc->realize) {
+        cdc->realize(cdev, vcdev->vdev.sysfsdev, errp);
+        if (*errp) {
+            return;
+        }
+    }
+
+    group = vfio_ccw_get_group(cdev, path, errp);
+    if (!group) {
+        goto out_group_err;
+    }
+
+    vcdev->vdev.ops = &vfio_ccw_ops;
+    vcdev->vdev.type = VFIO_DEVICE_TYPE_CCW;
+    vcdev->vdev.name = g_strdup_printf("%x.%x.%04x", cdev->hostid.cssid,
+                                       cdev->hostid.ssid, cdev->hostid.devid);
+    QLIST_FOREACH(vbasedev, &group->device_list, next) {
+        if (strcmp(vbasedev->name, vcdev->vdev.name) == 0) {
+            error_setg(errp, "vfio: subchannel %s has already been attached",
+                       basename(path[0]));
+            goto out_device_err;
+        }
+    }
+
+    if (vfio_get_device(group, cdev->mdevid, &vcdev->vdev, errp)) {
+        goto out_device_err;
+    }
+
+    return;
+
+out_device_err:
+    vfio_ccw_put_group(group, path);
+out_group_err:
+    if (cdc->unrealize) {
+        cdc->unrealize(cdev, errp);
+    }
+}
+
+static void vfio_ccw_unrealize(DeviceState *dev, Error **errp)
+{
+    CcwDevice *ccw_dev = DO_UPCAST(CcwDevice, parent_obj, dev);
+    S390CCWDevice *cdev = DO_UPCAST(S390CCWDevice, parent_obj, ccw_dev);
+    VFIOCCWDevice *vcdev = DO_UPCAST(VFIOCCWDevice, cdev, cdev);
+    S390CCWDeviceClass *cdc = S390_CCW_DEVICE_GET_CLASS(cdev);
+    VFIOGroup *group = vcdev->vdev.group;
+
+    if (cdc->unrealize) {
+        cdc->unrealize(cdev, errp);
+    }
+
+    vfio_put_device(vcdev);
+    vfio_put_group(group);
+}
+
+static Property vfio_ccw_properties[] = {
+    DEFINE_PROP_STRING("sysfsdev", VFIOCCWDevice, vdev.sysfsdev),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static const VMStateDescription vfio_ccw_vmstate = {
+    .name = TYPE_VFIO_CCW,
+    .unmigratable = 1,
+};
+
+static void vfio_ccw_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->props = vfio_ccw_properties;
+    dc->vmsd = &vfio_ccw_vmstate;
+    dc->desc = "VFIO-based subchannel assignment";
+    dc->realize = vfio_ccw_realize;
+    dc->unrealize = vfio_ccw_unrealize;
+    dc->reset = vfio_ccw_reset;
+}
+
+static const TypeInfo vfio_ccw_info = {
+    .name = TYPE_VFIO_CCW,
+    .parent = TYPE_S390_CCW,
+    .instance_size = sizeof(VFIOCCWDevice),
+    .class_init = vfio_ccw_class_init,
+};
+
+static void register_vfio_ccw_type(void)
+{
+    type_register_static(&vfio_ccw_info);
+}
+
+type_init(register_vfio_ccw_type)
diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h
index c582de1..9521013 100644
--- a/include/hw/vfio/vfio-common.h
+++ b/include/hw/vfio/vfio-common.h
@@ -45,6 +45,7 @@ 
 enum {
     VFIO_DEVICE_TYPE_PCI = 0,
     VFIO_DEVICE_TYPE_PLATFORM = 1,
+    VFIO_DEVICE_TYPE_CCW = 2,
 };
 
 typedef struct VFIOMmap {