Re: [Qemu-devel] [PATCH v5 07/13] vfio/ccw: vfio based subchannel passthrough driver

[Dong Jia Shi]

* Cornelia Huck  [2017-04-28 13:04:07 +0200]:

> On Wed, 26 Apr 2017 16:49:20 +0800
> Dong Jia Shi  wrote:
> 
> > * Dong Jia Shi  [2017-04-25 13:15:19 +0800]:
> > 
> > > * Alex Williamson  [2017-04-24 16:56:28 
> > > -0600]:
> > > 
> > > [...]
> > > > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > > > > new file mode 100644
> > > > > > index 000..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 
> > > > > > + *Xiao Feng Ren 
> > > > > > + *Pierre Morel 
> > > > > > + *
> > > > > > + * 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 
> > > > > > +#include 
> > > > > > +
> > > > > > +#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]

-- 
Dong Jia Shi

Re: [Qemu-devel] [PATCH v5 07/13] vfio/ccw: vfio based subchannel passthrough driver

[Cornelia Huck]

On Wed, 26 Apr 2017 16:49:20 +0800
Dong Jia Shi  wrote:

> * Dong Jia Shi  [2017-04-25 13:15:19 +0800]:
> 
> > * Alex Williamson  [2017-04-24 16:56:28 -0600]:
> > 
> > [...]
> > > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > > > new file mode 100644
> > > > > index 000..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 
> > > > > + *Xiao Feng Ren 
> > > > > + *Pierre Morel 
> > > > > + *
> > > > > + * 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 
> > > > > +#include 
> > > > > +
> > > > > +#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]

Re: [Qemu-devel] [PATCH v5 07/13] vfio/ccw: vfio based subchannel passthrough driver

[Dong Jia Shi]

* Dong Jia Shi  [2017-04-25 13:15:19 +0800]:

> * Alex Williamson  [2017-04-24 16:56:28 -0600]:
> 
> [...]
> > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > > new file mode 100644
> > > > index 000..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 
> > > > + *Xiao Feng Ren 
> > > > + *Pierre Morel 
> > > > + *
> > > > + * 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 
> > > > +#include 
> > > > +
> > > > +#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.

[...]

-- 
Dong Jia Shi

Re: [Qemu-devel] [PATCH v5 07/13] vfio/ccw: vfio based subchannel passthrough driver

[Dong Jia Shi]

* Alex Williamson  [2017-04-24 16:56:28 -0600]:

[...]
> > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> > > new file mode 100644
> > > index 000..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 
> > > + *Xiao Feng Ren 
> > > + *Pierre Morel 
> > > + *
> > > + * 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 
> > > +#include 
> > > +
> > > +#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(>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], ) < 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], ) < 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], );
> > > +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", ) != 1) {
> > > +error_setg(errp, "vfio: error reading %s:%m", path[3]);
> > > +return NULL;
> > > +}
> > > +
> > > +return vfio_get_group(groupid, _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 

Re: [Qemu-devel] [PATCH v5 07/13] vfio/ccw: vfio based subchannel passthrough driver

[Alex Williamson]

On Mon, 24 Apr 2017 16:43:38 -0600
Alex Williamson  wrote:

> On Wed, 12 Apr 2017 07:21:09 +0200
> Dong Jia Shi  wrote:
> 
> > From: Xiao Feng Ren 
> > 
> > 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=$mdev_file_path,devno=xx.x.'
> > 
> > Signed-off-by: Xiao Feng Ren 
> > Signed-off-by: Dong Jia Shi 
> > ---
> >  default-configs/s390x-softmmu.mak |   1 +
> >  hw/vfio/Makefile.objs |   1 +
> >  hw/vfio/ccw.c | 207 
> > ++
> >  include/hw/vfio/vfio-common.h |   1 +
> >  4 files changed, 210 insertions(+)
> >  create mode 100644 hw/vfio/ccw.c
> > 
> > diff --git a/default-configs/s390x-softmmu.mak 
> > b/default-configs/s390x-softmmu.mak
> > index 36e15de..5576b0a 100644
> > --- a/default-configs/s390x-softmmu.mak
> > +++ b/default-configs/s390x-softmmu.mak
> > @@ -4,4 +4,5 @@ CONFIG_VIRTIO=y
> >  CONFIG_SCLPCONSOLE=y
> >  CONFIG_S390_FLIC=y
> >  CONFIG_S390_FLIC_KVM=$(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 000..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 
> > + *Xiao Feng Ren 
> > + *Pierre Morel 
> > + *
> > + * 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 
> > +#include 
> > +
> > +#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(>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], ) < 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], ) < 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 

Re: [Qemu-devel] [PATCH v5 07/13] vfio/ccw: vfio based subchannel passthrough driver

[Alex Williamson]

On Wed, 12 Apr 2017 07:21:09 +0200
Dong Jia Shi  wrote:

> From: Xiao Feng Ren 
> 
> 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=$mdev_file_path,devno=xx.x.'
> 
> Signed-off-by: Xiao Feng Ren 
> Signed-off-by: Dong Jia Shi 
> ---
>  default-configs/s390x-softmmu.mak |   1 +
>  hw/vfio/Makefile.objs |   1 +
>  hw/vfio/ccw.c | 207 
> ++
>  include/hw/vfio/vfio-common.h |   1 +
>  4 files changed, 210 insertions(+)
>  create mode 100644 hw/vfio/ccw.c
> 
> diff --git a/default-configs/s390x-softmmu.mak 
> b/default-configs/s390x-softmmu.mak
> index 36e15de..5576b0a 100644
> --- a/default-configs/s390x-softmmu.mak
> +++ b/default-configs/s390x-softmmu.mak
> @@ -4,4 +4,5 @@ CONFIG_VIRTIO=y
>  CONFIG_SCLPCONSOLE=y
>  CONFIG_S390_FLIC=y
>  CONFIG_S390_FLIC_KVM=$(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 000..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 
> + *Xiao Feng Ren 
> + *Pierre Morel 
> + *
> + * 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 
> +#include 
> +
> +#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(>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], ) < 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], ) < 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], );
> +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", ) != 1) {
> +error_setg(errp, "vfio: error reading %s:%m", path[3]);
> +return NULL;
> +}
> +