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spapr: TCG allow up to 8-thread SMT on POWER8 and newer CPUs 

PPC TCG supports SMT CPU configurations for non-hypervisor state, so
permit POWER8-10 pseries machines to enable SMT.

This requires PIR and TIR be set, because that's how sibling thread
matching is done by TCG.

spapr's nested-HV capability does not currently coexist with SMT, so
that combination is prohibited (interestingly somewhat analogous to
LPAR-per-core mode on real hardware which also does not support KVM).

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
[ clg: Also test smp_threads when checking for POWER8 CPU and above ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
This commit is contained in:
Nicholas Piggin 2023-06-22 19:33:55 +10:00 committed by Cédric Le Goater
parent 516cd73733
commit dc5e072188
3 changed files with 32 additions and 6 deletions
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17
hw/ppc/spapr.c
View File

@ -2525,10 +2525,19 @@ static void spapr_set_vsmt_mode(SpaprMachineState *spapr, Error **errp)
int ret;
unsigned int smp_threads = ms->smp.threads;
if (tcg_enabled() && (smp_threads > 1)) {
error_setg(errp, "TCG cannot support more than 1 thread/core "
"on a pseries machine");
return;
if (tcg_enabled()) {
if (smp_threads > 1 &&
!ppc_type_check_compat(ms->cpu_type, CPU_POWERPC_LOGICAL_2_07, 0,
spapr->max_compat_pvr)) {
error_setg(errp, "TCG only supports SMT on POWER8 or newer CPUs");
return;
}
if (smp_threads > 8) {
error_setg(errp, "TCG cannot support more than 8 threads/core "
"on a pseries machine");
return;
}
}
if (!is_power_of_2(smp_threads)) {
error_setg(errp, "Cannot support %d threads/core on a pseries "

14
hw/ppc/spapr_caps.c
View File

@ -473,6 +473,20 @@ static void cap_nested_kvm_hv_apply(SpaprMachineState *spapr,
error_append_hint(errp,
"Try appending -machine cap-nested-hv=off\n");
}
} else if (tcg_enabled()) {
MachineState *ms = MACHINE(spapr);
unsigned int smp_threads = ms->smp.threads;
/*
* Nested-HV vCPU env state to L2, so SMT-shared SPR updates, for
* example, do not necessarily update the correct SPR value on sibling
* threads that are in a different guest/host context.
*/
if (smp_threads > 1) {
error_setg(errp, "TCG does not support nested-HV with SMT");
error_append_hint(errp, "Try appending -machine cap-nested-hv=off "
"or use threads=1 with -smp\n");
}
}
}

7
hw/ppc/spapr_cpu_core.c
View File

@ -255,7 +255,7 @@ static void spapr_cpu_core_unrealize(DeviceState *dev)
}
static bool spapr_realize_vcpu(PowerPCCPU *cpu, SpaprMachineState *spapr,
SpaprCpuCore *sc, Error **errp)
SpaprCpuCore *sc, int thread_index, Error **errp)
{
CPUPPCState *env = &cpu->env;
CPUState *cs = CPU(cpu);
@ -267,6 +267,9 @@ static bool spapr_realize_vcpu(PowerPCCPU *cpu, SpaprMachineState *spapr,
cpu_ppc_set_vhyp(cpu, PPC_VIRTUAL_HYPERVISOR(spapr));
kvmppc_set_papr(cpu);
env->spr_cb[SPR_PIR].default_value = cs->cpu_index;
env->spr_cb[SPR_TIR].default_value = thread_index;
/* Set time-base frequency to 512 MHz. vhyp must be set first. */
cpu_ppc_tb_init(env, SPAPR_TIMEBASE_FREQ);
@ -337,7 +340,7 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error **errp)
for (i = 0; i < cc->nr_threads; i++) {
sc->threads[i] = spapr_create_vcpu(sc, i, errp);
if (!sc->threads[i] ||
!spapr_realize_vcpu(sc->threads[i], spapr, sc, errp)) {
!spapr_realize_vcpu(sc->threads[i], spapr, sc, i, errp)) {
spapr_cpu_core_unrealize(dev);
return;
}