[v1,5/8] s390/sclp: use cpu offset to locate cpu entries

Commit Message

Collin Walling May 8, 2020, 11:08 p.m. UTC

The start of the CPU entry region in the Read SCP Info
response data is denoted by the offset_cpu field. As such,
QEMU needs to begin creating entries at this address.

This is in preparation for when Read SCP Info inevitably
introduces new bytes that push the start of its CPUEntry
field further away.

Read CPU Info is unlikely to ever change, so let's not
bother accounting for the offset there.

Signed-off-by: Collin Walling <[e-mail]>
---
 hw/s390x/sclp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Patch

diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index 748d04a0e2..c47bd3b5ab 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -103,15 +103,17 @@  static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
     int cpu_count;
     int rnsize, rnmax;
     IplParameterBlock *ipib = s390_ipl_get_iplb();
+    int offset_cpu = offsetof(ReadInfo, entries);
+    CPUEntry *entries_start = (void *)sccb + offset_cpu;
 
     if (!check_sufficient_sccb_len(sccb, sizeof(ReadInfo))) {
         return;
     }
 
     /* CPU information */
-    prepare_cpu_entries(read_info->entries, &cpu_count);
+    prepare_cpu_entries(entries_start, &cpu_count);
     read_info->entries_cpu = cpu_to_be16(cpu_count);
-    read_info->offset_cpu = cpu_to_be16(offsetof(ReadInfo, entries));
+    read_info->offset_cpu = cpu_to_be16(offset_cpu);
     read_info->highest_cpu = cpu_to_be16(machine->smp.max_cpus - 1);
 
     read_info->ibc_val = cpu_to_be32(s390_get_ibc_val());