Re: [PATCH v1 13/24] hw/s390x/ipl: Set iplb->len to maximum length of IPL Parameter Block

[Thomas Huth <thuth@redhat.com>]

On 08/04/2025 17.55, Zhuoying Cai wrote:
> The IPL Information Report Block (IIRB) immediately follows the IPL
> Parameter Block (IPLB).
> 
> The IPLB struct is allocated 4KB in memory, and iplb->len indicates
> the amount of memory currently used by the IPLB.
> 
> To ensure proper alignment of the IIRB and prevent overlap, set
> iplb->len to the maximum length of the IPLB, allowing alignment
> constraints to be determined based on its size.
> 
> Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
> ---
>   hw/s390x/ipl.c | 6 +++---
>   hw/s390x/ipl.h | 1 +
>   2 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> index 59ec81181d..b646fcc74e 100644
> --- a/hw/s390x/ipl.c
> +++ b/hw/s390x/ipl.c
> @@ -460,7 +460,7 @@ static bool s390_build_iplb(DeviceState *dev_st, IplParameterBlock *iplb)
>               if (scsi_lp && strlen(scsi_lp) > 0) {
>                   lp = scsi_lp;
>               }
> -            iplb->len = cpu_to_be32(S390_IPLB_MIN_QEMU_SCSI_LEN);
> +            iplb->len = cpu_to_be32(S390_IPLB_MAX_LEN);
>               iplb->blk0_len =
>                   cpu_to_be32(S390_IPLB_MIN_QEMU_SCSI_LEN - S390_IPLB_HEADER_LEN);
>               iplb->pbt = S390_IPL_TYPE_QEMU_SCSI;
> @@ -471,14 +471,14 @@ static bool s390_build_iplb(DeviceState *dev_st, IplParameterBlock *iplb)
>               iplb->scsi.ssid = ccw_dev->sch->ssid & 3;
>               break;
>           case CCW_DEVTYPE_VFIO:
> -            iplb->len = cpu_to_be32(S390_IPLB_MIN_CCW_LEN);
> +            iplb->len = cpu_to_be32(S390_IPLB_MAX_LEN);
>               iplb->pbt = S390_IPL_TYPE_CCW;
>               iplb->ccw.devno = cpu_to_be16(ccw_dev->sch->devno);
>               iplb->ccw.ssid = ccw_dev->sch->ssid & 3;
>               break;
>           case CCW_DEVTYPE_VIRTIO_NET:
>           case CCW_DEVTYPE_VIRTIO:
> -            iplb->len = cpu_to_be32(S390_IPLB_MIN_CCW_LEN);
> +            iplb->len = cpu_to_be32(S390_IPLB_MAX_LEN);
>               iplb->blk0_len =
>                   cpu_to_be32(S390_IPLB_MIN_CCW_LEN - S390_IPLB_HEADER_LEN);
>               iplb->pbt = S390_IPL_TYPE_CCW;

Wouldn't it make sense to only do this iff the secure IPL is also used?

  Thomas