diff mbox series

[v5,5/8] s390/sclp: use cpu offset to locate cpu entries

Message ID 20200910093655.255774-6-walling@linux.ibm.com
State Superseded
Headers show
Series s390: Extended-Length SCCB & DIAGNOSE 0x318 | expand

Commit Message

Collin Walling Sept. 10, 2020, 9:36 a.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 the 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 <walling@linux.ibm.com>
---
 hw/s390x/sclp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

Comments

Cornelia Huck Sept. 11, 2020, 10:36 a.m. UTC | #1
On Thu, 10 Sep 2020 05:36:52 -0400
Collin Walling <walling@linux.ibm.com> wrote:

> 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 the 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 <walling@linux.ibm.com>
> ---
>  hw/s390x/sclp.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
diff mbox series

Patch

diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index 12829bdd05..803fdd5ed4 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -89,6 +89,8 @@  static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
     int rnsize, rnmax;
     IplParameterBlock *ipib = s390_ipl_get_iplb();
     int required_len = SCCB_REQ_LEN(ReadInfo, machine->possible_cpus->len);
+    int offset_cpu = offsetof(ReadInfo, entries);
+    CPUEntry *entries_start = (void *)sccb + offset_cpu;
 
     if (be16_to_cpu(sccb->h.length) < required_len) {
         sccb->h.response_code = cpu_to_be16(SCLP_RC_INSUFFICIENT_SCCB_LENGTH);
@@ -96,9 +98,9 @@  static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
     }
 
     /* CPU information */
-    prepare_cpu_entries(machine, read_info->entries, &cpu_count);
+    prepare_cpu_entries(machine, 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());