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spapr: move VCPU calculation to core machine code

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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>
This commit is contained in:
Greg Kurz 2018-02-14 20:40:35 +01:00 • committed by David Gibson
parent 72194664c8
commit 648edb6475
3 changed files with 22 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

9
hw/ppc/spapr_cpu_core.c
View file

@ -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;
}