Re: [PATCH v14 04/11] s390x/sclp: reporting the maximum nested topology entries

[Thomas Huth]

On 05/01/2023 15.53, Pierre Morel wrote:
The maximum nested topology entries is used by the guest to know
how many nested topology are available on the machine.
Currently, SCLP READ SCP INFO reports MNEST = 0, which is the
equivalent of reporting the default value of 2.
Let's use the default SCLP value of 2 and increase this value in the
future patches implementing higher levels.

I'm confused ... so does a SCLP value of 2 mean a MNEST level of 4 ?

Signed-off-by: Pierre Morel <pmo...@linux.ibm.com>
---
  include/hw/s390x/sclp.h | 5 +++--
  hw/s390x/sclp.c         | 4 ++++
  2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/hw/s390x/sclp.h b/include/hw/s390x/sclp.h
index 712fd68123..4ce852473c 100644
--- a/include/hw/s390x/sclp.h
+++ b/include/hw/s390x/sclp.h
@@ -112,12 +112,13 @@ typedef struct CPUEntry {
  } QEMU_PACKED CPUEntry;
  
  #define SCLP_READ_SCP_INFO_FIXED_CPU_OFFSET     128
-#define SCLP_READ_SCP_INFO_MNEST                2
+#define SCLP_READ_SCP_INFO_MNEST                4

... since you update it to 4 here.

  typedef struct ReadInfo {
      SCCBHeader h;
      uint16_t rnmax;
      uint8_t rnsize;
-    uint8_t  _reserved1[16 - 11];       /* 11-15 */
+    uint8_t  _reserved1[15 - 11];       /* 11-14 */
+    uint8_t  stsi_parm;                 /* 15-16 */
      uint16_t entries_cpu;               /* 16-17 */
      uint16_t offset_cpu;                /* 18-19 */
      uint8_t  _reserved2[24 - 20];       /* 20-23 */
diff --git a/hw/s390x/sclp.c b/hw/s390x/sclp.c
index eff74479f4..07e3cb4cac 100644
--- a/hw/s390x/sclp.c
+++ b/hw/s390x/sclp.c
@@ -20,6 +20,7 @@
  #include "hw/s390x/event-facility.h"
  #include "hw/s390x/s390-pci-bus.h"
  #include "hw/s390x/ipl.h"
+#include "hw/s390x/cpu-topology.h"
  
  static inline SCLPDevice *get_sclp_device(void)
  {
@@ -125,6 +126,9 @@ static void read_SCP_info(SCLPDevice *sclp, SCCB *sccb)
  
      /* CPU information */
      prepare_cpu_entries(machine, entries_start, &cpu_count);
+    if (s390_has_topology()) {
+        read_info->stsi_parm = SCLP_READ_SCP_INFO_MNEST;

This seems to be in contradiction to what you've said in the commit 
description - you set it to 4 and not to 2.

 Thomas


+    }
      read_info->entries_cpu = cpu_to_be16(cpu_count);
      read_info->offset_cpu = cpu_to_be16(offset_cpu);
      read_info->highest_cpu = cpu_to_be16(machine->smp.max_cpus - 1);