From dc5e072188ea622071bab47c4f899817d6ef1295 Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 22 Jun 2023 19:33:55 +1000 Subject: [PATCH] spapr: TCG allow up to 8-thread SMT on POWER8 and newer CPUs MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Cédric Le Goater [ clg: Also test smp_threads when checking for POWER8 CPU and above ] Signed-off-by: Cédric Le Goater --- hw/ppc/spapr.c | 17 +++++++++++++---- hw/ppc/spapr_caps.c | 14 ++++++++++++++ hw/ppc/spapr_cpu_core.c | 7 +++++-- 3 files changed, 32 insertions(+), 6 deletions(-) diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 8e7d497f25..54dbfd7fe9 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -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 " diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c index 3fd45a6dec..5a0755d34f 100644 --- a/hw/ppc/spapr_caps.c +++ b/hw/ppc/spapr_caps.c @@ -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"); + } } } diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c index 9b88dd549a..a4e3c2fadd 100644 --- a/hw/ppc/spapr_cpu_core.c +++ b/hw/ppc/spapr_cpu_core.c @@ -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; }