Re: [Qemu-devel] [PATCH v3 01/16] s390 vfio-ccw: Add bootindex property and IPLB data

[Cornelia Huck <cohuck@redhat.com>]

On Fri,  1 Mar 2019 13:59:21 -0500
"Jason J. Herne" <jjherne@linux.ibm.com> wrote:

> Add bootindex property and iplb data for vfio-ccw devices. This allows us to
> forward boot information into the bios for vfio-ccw devices.
> 
> Refactor s390_get_ccw_device() to return device type. This prevents us from
> having to use messy casting logic in several places.
> 
> Signed-off-by: Jason J. Herne <jjherne@linux.ibm.com>
> Acked-by: Halil Pasic <pasic@linux.vnet.ibm.com>
> ---
>  MAINTAINERS                 |  1 +
>  hw/s390x/ipl.c              | 39 +++++++++++++++++++++++++++++++++------
>  hw/s390x/s390-ccw.c         |  9 +++++++++
>  hw/vfio/ccw.c               |  2 +-
>  include/hw/s390x/s390-ccw.h |  1 +
>  include/hw/s390x/vfio-ccw.h | 28 ++++++++++++++++++++++++++++
>  6 files changed, 73 insertions(+), 7 deletions(-)
>  create mode 100644 include/hw/s390x/vfio-ccw.h
> 
(...)
> @@ -305,16 +306,29 @@ static void s390_ipl_set_boot_menu(S390IPLState *ipl)
>      *timeout = cpu_to_be32(splash_time);
>  }
>  
> -static CcwDevice *s390_get_ccw_device(DeviceState *dev_st)
> +#define CCW_DEVTYPE_NONE    0x00
> +#define CCW_DEVTYPE_VIRTIO  0x01
> +#define CCW_DEVTYPE_SCSI    0x02
> +#define CCW_DEVTYPE_VFIO    0x03

Hm, how would the code look if you introduced a CCW_DEVTYPE_VIRTIO_NET
or so? You could use the simply set the netboot flag in
get_initial_iplb and fall through to the handling of
CCW_DEVTYPE_VIRTIO...

> +
> +static CcwDevice *s390_get_ccw_device(DeviceState *dev_st, int* devtype)

s/int* devtype/int *devtype/

>  {
>      CcwDevice *ccw_dev = NULL;
>  
> +    *devtype = CCW_DEVTYPE_NONE;
> +
>      if (dev_st) {
>          VirtioCcwDevice *virtio_ccw_dev = (VirtioCcwDevice *)
>              object_dynamic_cast(OBJECT(qdev_get_parent_bus(dev_st)->parent),
>                                  TYPE_VIRTIO_CCW_DEVICE);
> +        VFIOCCWDevice *vfio_ccw_dev = (VFIOCCWDevice *)
> +            object_dynamic_cast(OBJECT(dev_st), TYPE_VFIO_CCW);
>          if (virtio_ccw_dev) {
>              ccw_dev = CCW_DEVICE(virtio_ccw_dev);
> +            *devtype = CCW_DEVTYPE_VIRTIO;
> +        } else if (vfio_ccw_dev) {
> +            ccw_dev = CCW_DEVICE(vfio_ccw_dev);
> +            *devtype = CCW_DEVTYPE_VFIO;
>          } else {
>              SCSIDevice *sd = (SCSIDevice *)
>                  object_dynamic_cast(OBJECT(dev_st),
> @@ -327,6 +341,7 @@ static CcwDevice *s390_get_ccw_device(DeviceState *dev_st)
>  
>                  ccw_dev = (CcwDevice *)object_dynamic_cast(OBJECT(scsi_ccw),
>                                                             TYPE_CCW_DEVICE);
> +                *devtype = CCW_DEVTYPE_SCSI;
>              }
>          }
>      }
> @@ -337,10 +352,11 @@ static bool s390_gen_initial_iplb(S390IPLState *ipl)
>  {
>      DeviceState *dev_st;
>      CcwDevice *ccw_dev = NULL;
> +    int devtype;
>  
>      dev_st = get_boot_device(0);
>      if (dev_st) {
> -        ccw_dev = s390_get_ccw_device(dev_st);
> +        ccw_dev = s390_get_ccw_device(dev_st, &devtype);
>      }
>  
>      /*
> @@ -349,8 +365,10 @@ static bool s390_gen_initial_iplb(S390IPLState *ipl)
>      if (ccw_dev) {
>          SCSIDevice *sd = (SCSIDevice *) object_dynamic_cast(OBJECT(dev_st),
>                                                              TYPE_SCSI_DEVICE);
> +        VirtIONet *vn;

I think you could get rid of this variable with my suggestion from
above.

>  
> -        if (sd) {
> +        switch (devtype) {
> +        case CCW_DEVTYPE_SCSI:

Move obtaining sd into this case?

>              ipl->iplb.len = cpu_to_be32(S390_IPLB_MIN_QEMU_SCSI_LEN);
>              ipl->iplb.blk0_len =
>                  cpu_to_be32(S390_IPLB_MIN_QEMU_SCSI_LEN - S390_IPLB_HEADER_LEN);
> @@ -360,8 +378,15 @@ static bool s390_gen_initial_iplb(S390IPLState *ipl)
>              ipl->iplb.scsi.channel = cpu_to_be16(sd->channel);
>              ipl->iplb.scsi.devno = cpu_to_be16(ccw_dev->sch->devno);
>              ipl->iplb.scsi.ssid = ccw_dev->sch->ssid & 3;
> -        } else {
> -            VirtIONet *vn = (VirtIONet *) object_dynamic_cast(OBJECT(dev_st),
> +            break;
> +        case CCW_DEVTYPE_VFIO:
> +            ipl->iplb.len = cpu_to_be32(S390_IPLB_MIN_CCW_LEN);
> +            ipl->iplb.pbt = S390_IPL_TYPE_CCW;
> +            ipl->iplb.ccw.devno = cpu_to_be16(ccw_dev->sch->devno);
> +            ipl->iplb.ccw.ssid = ccw_dev->sch->ssid & 3;
> +            break;
> +        case CCW_DEVTYPE_VIRTIO:
> +            vn = (VirtIONet *) object_dynamic_cast(OBJECT(dev_st),
>                                                                TYPE_VIRTIO_NET);
>  
>              ipl->iplb.len = cpu_to_be32(S390_IPLB_MIN_CCW_LEN);
> @@ -374,6 +399,7 @@ static bool s390_gen_initial_iplb(S390IPLState *ipl)
>              if (vn) {
>                  ipl->netboot = true;
>              }
> +            break;
>          }
>  
>          if (!s390_ipl_set_loadparm(ipl->iplb.loadparm)) {
> @@ -518,6 +544,7 @@ IplParameterBlock *s390_ipl_get_iplb(void)
>  void s390_ipl_reset_request(CPUState *cs, enum s390_reset reset_type)
>  {
>      S390IPLState *ipl = get_ipl_device();
> +    int devtype;
>  
>      if (reset_type == S390_RESET_EXTERNAL || reset_type == S390_RESET_REIPL) {
>          /* use CPU 0 for full resets */
> @@ -532,7 +559,7 @@ void s390_ipl_reset_request(CPUState *cs, enum s390_reset reset_type)
>          !ipl->netboot &&
>          ipl->iplb.pbt == S390_IPL_TYPE_CCW &&
>          is_virtio_scsi_device(&ipl->iplb)) {
> -        CcwDevice *ccw_dev = s390_get_ccw_device(get_boot_device(0));
> +        CcwDevice *ccw_dev = s390_get_ccw_device(get_boot_device(0), &devtype);

It feels wrong to have a variable that is not used later... what about
either
- making s390_get_ccw_device() capable of handling a NULL second
  parameter, or
- (what I think would be nicer) passing in the devtype as an optional
  parameter to gen_initial_iplb() so you don't need to do the casting
  dance twice?

>  
>          if (ccw_dev &&
>              cpu_to_be16(ccw_dev->sch->devno) == ipl->iplb.ccw.devno &&