spapr: move VCPU calculation to core machine code

The VCPU ids are currently computed and assigned to each individual
CPU threads in spapr_cpu_core_realize(). But the numbering logic
of VCPU ids is actually a machine-level concept, and many places
in hw/ppc/spapr.c also have to compute VCPU ids out of CPU indexes.

The current formula used in spapr_cpu_core_realize() is:

    vcpu_id = (cc->core_id * spapr->vsmt / smp_threads) + i

where:

    cc->core_id is a multiple of smp_threads
    cpu_index = cc->core_id + i
    0 <= i < smp_threads

So we have:

    cpu_index % smp_threads == i
    cc->core_id / smp_threads == cpu_index / smp_threads

hence:

    vcpu_id =
        (cpu_index / smp_threads) * spapr->vsmt + cpu_index % smp_threads;

This formula was used before VSMT at the time VCPU ids where computed
at the target emulation level. It has the advantage of being useable
to derive a VPCU id out of a CPU index only. It is fitted for all the
places where the machine code has to compute a VCPU id.

This patch introduces an accessor to set the VCPU id in a PowerPCCPU object
using the above formula. It is a first step to consolidate all the VCPU id
logic in a single place.

Signed-off-by: Greg Kurz <groug@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

2 files changed, 21 insertions, 7 deletions

diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index ea7429c92a..30cc48fd52 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3802,6 +3802,25 @@ int spapr_vcpu_id(PowerPCCPU *cpu)
     }
 }
 
+void spapr_set_vcpu_id(PowerPCCPU *cpu, int cpu_index, Error **errp)
+{
+    sPAPRMachineState *spapr = SPAPR_MACHINE(qdev_get_machine());
+    int vcpu_id;
+
+    vcpu_id =
+        (cpu_index / smp_threads) * spapr->vsmt + cpu_index % smp_threads;
+
+    if (kvm_enabled() && !kvm_vcpu_id_is_valid(vcpu_id)) {
+        error_setg(errp, "Can't create CPU with id %d in KVM", vcpu_id);
+        error_append_hint(errp, "Adjust the number of cpus to %d "
+                          "or try to raise the number of threads per core\n",
+                          vcpu_id * smp_threads / spapr->vsmt);
+        return;
+    }
+
+    cpu->vcpu_id = vcpu_id;
+}
+
 PowerPCCPU *spapr_find_cpu(int vcpu_id)
 {
     CPUState *cs;
diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 590d167b04..94afeb399e 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -172,13 +172,8 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
         cs = CPU(obj);
         cpu = sc->threads[i] = POWERPC_CPU(obj);
         cs->cpu_index = cc->core_id + i;
-        cpu->vcpu_id = (cc->core_id * spapr->vsmt / smp_threads) + i;
-        if (kvm_enabled() && !kvm_vcpu_id_is_valid(cpu->vcpu_id)) {
-            error_setg(&local_err, "Can't create CPU with id %d in KVM",
-                       cpu->vcpu_id);
-            error_append_hint(&local_err, "Adjust the number of cpus to %d "
-                              "or try to raise the number of threads per core\n",
-                              cpu->vcpu_id * smp_threads / spapr->vsmt);
+        spapr_set_vcpu_id(cpu, cs->cpu_index, &local_err);
+        if (local_err) {
             goto err;
         }