Re: [PATCH v4 2/5] spapr_numa.c: split FORM1 code into helpers

[Daniel Henrique Barboza]

On 9/6/21 9:30 PM, David Gibson wrote:

On Fri, Aug 27, 2021 at 06:24:52AM -0300, Daniel Henrique Barboza wrote:

The upcoming FORM2 NUMA affinity will support asymmetric NUMA topologies
and doesn't need be concerned with all the legacy support for older
pseries FORM1 guests.

We're also not going to calculate associativity domains based on numa
distance (via spapr_numa_define_associativity_domains) since the
distances will be written directly into new DT properties.

Let's split FORM1 code into its own functions to allow for easier
insertion of FORM2 logic later on.

Reviewed-by: Greg Kurz <gr...@kaod.org>
Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com>
---
  hw/ppc/spapr_numa.c | 61 +++++++++++++++++++++++++++++----------------
  1 file changed, 39 insertions(+), 22 deletions(-)

diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
index 779f18b994..04a86f9b5b 100644
--- a/hw/ppc/spapr_numa.c
+++ b/hw/ppc/spapr_numa.c
@@ -155,6 +155,32 @@ static void 
spapr_numa_define_associativity_domains(SpaprMachineState *spapr)

} +/*

+ * Set NUMA machine state data based on FORM1 affinity semantics.
+ */
+static void spapr_numa_FORM1_affinity_init(SpaprMachineState *spapr,
+                                           MachineState *machine)
+{
+    bool using_legacy_numa = spapr_machine_using_legacy_numa(spapr);
+
+    /*
+     * Legacy NUMA guests (pseries-5.1 and older, or guests with only
+     * 1 NUMA node) will not benefit from anything we're going to do
+     * after this point.
+     */
+    if (using_legacy_numa) {
+        return;
+    }

My only concern with this patch is that handling the
"using_legacy_numa" case might logically belong outside the FORM1
code.  I mean, I'm pretty sure using_legacy_numa implies FORM1 in
practice, but conceptually it seems like a more fundamental question
than the DT encoding of the NUMA information.

I'll carry on this suggestion for the next spin, v6, given that the v5 I sent
a few minutes ago is also verifying legacy numa in FORM1 code.


Thanks,


Daniel

+
+    if (!spapr_numa_is_symmetrical(machine)) {
+        error_report("Asymmetrical NUMA topologies aren't supported "
+                     "in the pSeries machine");
+        exit(EXIT_FAILURE);
+    }
+
+    spapr_numa_define_associativity_domains(spapr);
+}
+
  void spapr_numa_associativity_init(SpaprMachineState *spapr,
                                     MachineState *machine)
  {
@@ -210,22 +236,7 @@ void spapr_numa_associativity_init(SpaprMachineState 
*spapr,
          spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i);
      }

- /*

-     * Legacy NUMA guests (pseries-5.1 and older, or guests with only
-     * 1 NUMA node) will not benefit from anything we're going to do
-     * after this point.
-     */
-    if (using_legacy_numa) {
-        return;
-    }
-
-    if (!spapr_numa_is_symmetrical(machine)) {
-        error_report("Asymmetrical NUMA topologies aren't supported "
-                     "in the pSeries machine");
-        exit(EXIT_FAILURE);
-    }
-
-    spapr_numa_define_associativity_domains(spapr);
+    spapr_numa_FORM1_affinity_init(spapr, machine);
  }

void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,

@@ -302,12 +313,8 @@ int spapr_numa_write_assoc_lookup_arrays(SpaprMachineState 
*spapr, void *fdt,
      return ret;
  }

-/*

- * Helper that writes ibm,associativity-reference-points and
- * max-associativity-domains in the RTAS pointed by @rtas
- * in the DT @fdt.
- */
-void spapr_numa_write_rtas_dt(SpaprMachineState *spapr, void *fdt, int rtas)
+static void spapr_numa_FORM1_write_rtas_dt(SpaprMachineState *spapr,
+                                           void *fdt, int rtas)
  {
      MachineState *ms = MACHINE(spapr);
      SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
@@ -365,6 +372,16 @@ void spapr_numa_write_rtas_dt(SpaprMachineState *spapr, 
void *fdt, int rtas)
                       maxdomains, sizeof(maxdomains)));
  }

+/*

+ * Helper that writes ibm,associativity-reference-points and
+ * max-associativity-domains in the RTAS pointed by @rtas
+ * in the DT @fdt.
+ */
+void spapr_numa_write_rtas_dt(SpaprMachineState *spapr, void *fdt, int rtas)
+{
+    spapr_numa_FORM1_write_rtas_dt(spapr, fdt, rtas);
+}
+
  static target_ulong h_home_node_associativity(PowerPCCPU *cpu,
                                                SpaprMachineState *spapr,
                                                target_ulong opcode,