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Re: [PATCH v8 02/12] s390x/cpu_topology: CPU topology objects and struct

From: Pierre Morel
Subject: Re: [PATCH v8 02/12] s390x/cpu_topology: CPU topology objects and structures
Date: Wed, 29 Jun 2022 17:25:19 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0

On 6/27/22 15:31, Janosch Frank wrote:
On 6/20/22 16:03, Pierre Morel wrote:
We use new objects to have a dynamic administration of the CPU topology.
The highest level object in this implementation is the s390 book and
in this first implementation of CPU topology for S390 we have a single
The book is built as a SYSBUS bridge during the CPU initialization.
Other objects, sockets and core will be built after the parsing
of the QEMU -smp argument.

Every object under this single book will be build dynamically
immediately after a CPU has be realized if it is needed.
The CPU will fill the sockets once after the other, according to the
number of core per socket defined during the smp parsing.

Each CPU inside a socket will be represented by a bit in a 64bit
unsigned long. Set on plug and clear on unplug of a CPU.

For the S390 CPU topology, thread and cores are merged into
topology cores and the number of topology cores is the multiplication
of cores by the numbers of threads.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>


diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index 7d6d01325b..216adfde26 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -565,6 +565,53 @@ typedef union SysIB {
  } SysIB;
  QEMU_BUILD_BUG_ON(sizeof(SysIB) != 4096);
+/* CPU type Topology List Entry */
+typedef struct SysIBTl_cpu {
+        uint8_t nl;
+        uint8_t reserved0[3];
+        uint8_t reserved1:5;
+        uint8_t dedicated:1;
+        uint8_t polarity:2;
+        uint8_t type;
+        uint16_t origin;
+        uint64_t mask;
+} SysIBTl_cpu;
+QEMU_BUILD_BUG_ON(sizeof(SysIBTl_cpu) != 16);
+/* Container type Topology List Entry */
+typedef struct SysIBTl_container {
+        uint8_t nl;
+        uint8_t reserved[6];
+        uint8_t id;
+} QEMU_PACKED SysIBTl_container;
+QEMU_BUILD_BUG_ON(sizeof(SysIBTl_container) != 8);
+/* Generic Topology List Entry */
+typedef union SysIBTl_entry {
+        uint8_t nl;

This union member is unused, isn't it?

+        SysIBTl_container container;
+        SysIBTl_cpu cpu;
+} SysIBTl_entry;
+#define TOPOLOGY_NR_MAG  6


+#define TOPOLOGY_NR_MAG6 0


I'm open to other suggestions but we need to differentiate between the number of mag array entries and the number of TLEs in the MAGs.

typedef enum {
        TOPOLOGY_MAG6 = 0,
        TOPOLOGY_MAG5 = 1,
        TOPOLOGY_MAG4 = 2,
        TOPOLOGY_MAG3 = 3,
        TOPOLOGY_MAG2 = 4,
        TOPOLOGY_MAG1 = 5,

oder enum with TOPOLOGY_NR_TLES_MAGx ?

+#define TOPOLOGY_NR_MAG5 1
+#define TOPOLOGY_NR_MAG4 2
+#define TOPOLOGY_NR_MAG3 3
+#define TOPOLOGY_NR_MAG2 4
+#define TOPOLOGY_NR_MAG1 5

I'd appreciate a \n here.


+/* Configuration topology */
+typedef struct SysIB_151x {
+    uint8_t  res0[2];

You're using "reserved" everywhere but now it's "rev"?

OK I will keep reserved

+    uint16_t length;
+    uint8_t  mag[TOPOLOGY_NR_MAG];
+    uint8_t  res1;
+    uint8_t  mnest;
+    uint32_t res2;
+    SysIBTl_entry tle[0];
+} SysIB_151x;
+QEMU_BUILD_BUG_ON(sizeof(SysIB_151x) != 16);
  /* MMU defines */
  #define ASCE_ORIGIN           (~0xfffULL) /* segment table origin             */   #define ASCE_SUBSPACE         0x200       /* subspace group control           */

Pierre Morel
IBM Lab Boeblingen

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