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 <address@hidden> wrote:

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