Re: [PATCH RFC v2 08/12] vfio/ccw: get io region info

[Alex Williamson <alex.williamson@redhat.com>]

On Thu, 12 Jan 2017 08:25:09 +0100
Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com> wrote:

> vfio-ccw provides an MMIO region for I/O operations. We fetch its
> information via ioctls here, then we can use it performing I/O
> instructions and retrieving I/O results later on.
> 
> Signed-off-by: Xiao Feng Ren <renxiaof@linux.vnet.ibm.com>
> ---
>  hw/vfio/ccw.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c
> index 881010b..93394c2 100644
> --- a/hw/vfio/ccw.c
> +++ b/hw/vfio/ccw.c
> @@ -21,11 +21,15 @@
>  #include "hw/vfio/vfio-common.h"
>  #include "hw/s390x/s390-ccw.h"
>  #include "hw/s390x/ccw-device.h"
> +#include "standard-headers/asm-s390/vfio_ccw.h"
>  
>  #define TYPE_VFIO_CCW "vfio-ccw"
>  typedef struct VFIOCCWDevice {
>      S390CCWDevice cdev;
>      VFIODevice vdev;
> +    uint64_t io_region_size;
> +    uint64_t io_region_offset;
> +    struct ccw_io_region *io_region;
>  } VFIOCCWDevice;
>  
>  static void vfio_ccw_compute_needs_reset(VFIODevice *vdev)
> @@ -50,6 +54,46 @@ static void vfio_ccw_reset(DeviceState *dev)
>      ioctl(vcdev->vdev.fd, VFIO_DEVICE_RESET);
>  }
>  
> +static void vfio_ccw_get_region(VFIOCCWDevice *vcdev, Error **errp)
> +{
> +    VFIODevice *vdev = &vcdev->vdev;
> +    struct vfio_region_info *info;
> +    int ret;
> +
> +    /* Sanity check device */
> +    if (!(vdev->flags & VFIO_DEVICE_FLAGS_CCW)) {
> +        error_setg(errp, "vfio: Um, this isn't a vfio-ccw device");
> +        return;
> +    }
> +
> +    if (vdev->num_regions != VFIO_CCW_NUM_REGIONS) {
> +        error_setg(errp, "vfio: Unexpected number of the I/O region %u",
> +                   vdev->num_regions);
> +        return;
> +    }

I think you want < here, not !=, otherwise you we can never add another
region to describe something new on a vfio-ccw device without breaking
this code.  You've defined in the uapi that region index zero is always
VFIO_CCW_CONFIG_REGION_INDEX and this code only depends on that, no
matter what additional regions might be added.  That's done below.

> +
> +    ret = vfio_get_region_info(vdev, VFIO_CCW_CONFIG_REGION_INDEX, &info);
> +    if (ret) {
> +        error_setg(errp, "vfio: Error getting config info: %d", ret);
> +        return;
> +    }
> +
> +    vcdev->io_region_size = info->size;
> +    if (sizeof(*vcdev->io_region) != vcdev->io_region_size) {
> +        error_setg(errp, "vfio: Unexpected size of the I/O region");
> +        return;
> +    }
> +    vcdev->io_region_offset = info->offset;
> +    vcdev->io_region = g_malloc0(info->size);
> +
> +    g_free(info);
> +}
> +
> +static void vfio_ccw_put_region(VFIOCCWDevice *vcdev)
> +{
> +    g_free(vcdev->io_region);
> +}
> +
>  static void vfio_put_device(VFIOCCWDevice *vcdev)
>  {
>      g_free(vcdev->vdev.name);
> @@ -144,8 +188,15 @@ static void vfio_ccw_realize(DeviceState *dev, Error **errp)
>          goto out_device_err;
>      }
>  
> +    vfio_ccw_get_region(vcdev, errp);
> +    if (*errp) {
> +        goto out_region_err;
> +    }
> +
>      return;
>  
> +out_region_err:
> +    vfio_put_device(vcdev);
>  out_device_err:
>      vfio_ccw_put_group(group, path);
>  out_group_err:
> @@ -166,6 +217,7 @@ static void vfio_ccw_unrealize(DeviceState *dev, Error **errp)
>          cdc->unrealize(cdev, errp);
>      }
>  
> +    vfio_ccw_put_region(vcdev);
>      vfio_put_device(vcdev);
>      vfio_put_group(group);
>  }