Re: [PATCH v5 16/29] hw/s390x/ipl: Set iplb->len to maximum length of IPL Parameter Block

[Jared Rossi]

On 8/18/25 5:43 PM, 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 <zy...@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 8ac0cee73d..d1a972ac8d 100644
--- a/hw/s390x/ipl.c
+++ b/hw/s390x/ipl.c
@@ -459,7 +459,7 @@ 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;
@@ -470,14 +470,14 @@ 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;
diff --git a/hw/s390x/ipl.h b/hw/s390x/ipl.h
index 3b8cc5474e..01922d80c4 100644
--- a/hw/s390x/ipl.h
+++ b/hw/s390x/ipl.h
@@ -100,6 +100,7 @@ QEMU_BUILD_BUG_MSG(offsetof(S390IPLState, iplb) & 3, "alignment 
of iplb wrong");
  #define S390_IPLB_MIN_CCW_LEN 200
  #define S390_IPLB_MIN_FCP_LEN 384
  #define S390_IPLB_MIN_QEMU_SCSI_LEN 200
+#define S390_IPLB_MAX_LEN 4096

static inline bool diag_parm_addr_valid(uint64_t addr, size_t size, bool write)

  {

This only needs to be done if the IIRB exists.  See comments on patch 15.

Regards,
Jared Rossi