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Re: [PATCH v16 03/11] target/s390x/cpu topology: handle STSI(15) and bui


From: Pierre Morel
Subject: Re: [PATCH v16 03/11] target/s390x/cpu topology: handle STSI(15) and build the SYSIB
Date: Wed, 8 Mar 2023 16:24:17 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0


On 2/27/23 14:21, Nina Schoetterl-Glausch wrote:
On Wed, 2023-02-22 at 15:20 +0100, Pierre Morel wrote:
On interception of STSI(15.1.x) the System Information Block
(SYSIB) is built from the list of pre-ordered topology entries.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
  include/hw/s390x/cpu-topology.h |  21 +++
  include/hw/s390x/sclp.h         |   1 +
  target/s390x/cpu.h              |  72 ++++++++
  hw/s390x/cpu-topology.c         |  14 +-
  target/s390x/kvm/cpu_topology.c | 312 ++++++++++++++++++++++++++++++++
  target/s390x/kvm/kvm.c          |   5 +-
  target/s390x/kvm/meson.build    |   3 +-
  7 files changed, 425 insertions(+), 3 deletions(-)
  create mode 100644 target/s390x/kvm/cpu_topology.c

diff --git a/include/hw/s390x/cpu-topology.h b/include/hw/s390x/cpu-topology.h
index fa7f885a9f..8dc42d2942 100644
--- a/include/hw/s390x/cpu-topology.h
+++ b/include/hw/s390x/cpu-topology.h
@@ -16,8 +16,29 @@
#define S390_TOPOLOGY_CPU_IFL 0x03 +typedef union s390_topology_id {
+    uint64_t id;
+    struct {
+        uint8_t level5;
You could rename this to sentinel, since that's the only use case and
if there ever is another level the sentinel implementation might need
to be changed anyway.


OK



+        uint8_t drawer;
+        uint8_t book;
+        uint8_t socket;
+        uint8_t dedicated;
+        uint8_t entitlement;
+        uint8_t type;
+        uint8_t origin;
+    };
+} s390_topology_id;
+

[...]

diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index d654267a71..c899f4e04b 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -560,6 +560,25 @@ typedef struct SysIB_322 {

[...]
+/*
+ * CPU Topology List provided by STSI with fc=15 provides a list
+ * of two different Topology List Entries (TLE) types to specify
+ * the topology hierarchy.
+ *
+ * - Container Topology List Entry
+ *   Defines a container to contain other Topology List Entries
+ *   of any type, nested containers or CPU.
+ * - CPU Topology List Entry
+ *   Specifies the CPUs position, type, entitlement and polarization
+ *   of the CPUs contained in the last Container TLE.
+ *
+ * There can be theoretically up to five levels of containers, QEMU
+ * uses only three levels, the drawer's, book's and socket's level.
+ *
+ * A container of with a nesting level (NL) greater than 1 can only
s/of//


thanks.



+ * contain another container of nesting level NL-1.
+ *
+ * A container of nesting level 1 (socket), contains as many CPU TLE
+ * as needed to describe the position and qualities of all CPUs inside
+ * the container.
+ * The qualities of a CPU are polarization, entitlement and type.
+ *
+ * The CPU TLE defines the position of the CPUs of identical qualities
+ * using a 64bits mask which first bit has its offset defined by
+ * the CPU address orgin field of the CPU TLE like in:
+ * CPU address = origin * 64 + bit position within the mask
+ *
+ */
+/* Container type Topology List Entry */
+typedef struct SysIBTl_container {
+        uint8_t nl;
+        uint8_t reserved[6];
+        uint8_t id;
+} QEMU_PACKED QEMU_ALIGNED(8) SysIBTl_container;
+QEMU_BUILD_BUG_ON(sizeof(SysIBTl_container) != 8);
+
[...]
+
+/**
+ * s390_topology_from_cpu:
+ * @cpu: The S390CPU
+ *
+ * Initialize the topology id from the CPU environment.
+ */
+static s390_topology_id s390_topology_from_cpu(S390CPU *cpu)
+{
+    s390_topology_id topology_id = {0};
+
+    topology_id.drawer = cpu->env.drawer_id;
+    topology_id.book = cpu->env.book_id;
+    topology_id.socket = cpu->env.socket_id;
+    topology_id.origin = cpu->env.core_id / 64;
+    topology_id.type = S390_TOPOLOGY_CPU_IFL;
+    topology_id.dedicated = cpu->env.dedicated;
+
+    if (s390_topology.polarization == S390_CPU_POLARIZATION_VERTICAL) {
+        /*
+         * Vertical polarization with dedicated CPU implies
+         * vertical high entitlement.
+         */
+        if (topology_id.dedicated) {
+            topology_id.entitlement = S390_CPU_ENTITLEMENT_HIGH;
+        } else {
+            topology_id.entitlement = cpu->env.entitlement;
+        }
I don't see why you need this if, it should already be correct.

+    }
I'd suggest the following:
* rename entitlement in s390_topology_id back to polarization, but keep 
entitlement everywhere else.
* remove horizontal/none from CpuS390Entitlement, this way the user cannot set 
it,
        and it doesn't show up in the output of query-cpus-fast.
* this is where you convert between the two, so:
        if horizontal, id.polarization = 0,
        otherwise id.polarization = entitlement + 1, or a switch case.
* in patch 6 in s390_topology_set_cpus_entitlement you don't set the 
entitlement if the polarization
        is horizontal, which is ok because of the conversion above.

I do not like to remove the horizontal entitlement from the enum because every existing s390 tool show "horizontal" entitlement when the polarization is horizontal.

See, lscpu -e or "/sys/devices/system/cpu/cpu*/polarization"

Also, the user may find strange that a field is missing depending of the polarization in the output of query-cpu-fast.

Regards,

Pierre





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