hw/core/machine-smp.c

   1 /*
   2  * QEMU Machine core (related to -smp parsing)
   3  *
   4  * Copyright (c) 2021 Huawei Technologies Co., Ltd
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License,
   9  * or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "qemu/osdep.h"
  21 #include "hw/boards.h"
  22 #include "qapi/error.h"
  23
  24 /*
  25  * Report information of a machine's supported CPU topology hierarchy.
  26  * Topology members will be ordered from the largest to the smallest
  27  * in the string.
  28  */
  29 static char *cpu_hierarchy_to_string(MachineState *ms)
  30 {
  31     MachineClass *mc = MACHINE_GET_CLASS(ms);
  32     GString *s = g_string_new(NULL);
  33
  34     g_string_append_printf(s, "sockets (%u)", ms->smp.sockets);
  35
  36     if (mc->smp_props.dies_supported) {
  37         g_string_append_printf(s, " * dies (%u)", ms->smp.dies);
  38     }
  39
  40     g_string_append_printf(s, " * cores (%u)", ms->smp.cores);
  41     g_string_append_printf(s, " * threads (%u)", ms->smp.threads);
  42
  43     return g_string_free(s, false);
  44 }
  45
  46 /*
  47  * smp_parse - Generic function used to parse the given SMP configuration
  48  *
  49  * Any missing parameter in "cpus/maxcpus/sockets/cores/threads" will be
  50  * automatically computed based on the provided ones.
  51  *
  52  * In the calculation of omitted sockets/cores/threads: we prefer sockets
  53  * over cores over threads before 6.2, while preferring cores over sockets
  54  * over threads since 6.2.
  55  *
  56  * In the calculation of cpus/maxcpus: When both maxcpus and cpus are omitted,
  57  * maxcpus will be computed from the given parameters and cpus will be set
  58  * equal to maxcpus. When only one of maxcpus and cpus is given then the
  59  * omitted one will be set to its given counterpart's value. Both maxcpus and
  60  * cpus may be specified, but maxcpus must be equal to or greater than cpus.
  61  *
  62  * For compatibility, apart from the parameters that will be computed, newly
  63  * introduced topology members which are likely to be target specific should
  64  * be directly set as 1 if they are omitted (e.g. dies for PC since 4.1).
  65  */
  66 void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
  67 {
  68     MachineClass *mc = MACHINE_GET_CLASS(ms);
  69     unsigned cpus    = config->has_cpus ? config->cpus : 0;
  70     unsigned sockets = config->has_sockets ? config->sockets : 0;
  71     unsigned dies    = config->has_dies ? config->dies : 0;
  72     unsigned cores   = config->has_cores ? config->cores : 0;
  73     unsigned threads = config->has_threads ? config->threads : 0;
  74     unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
  75
  76     /*
  77      * Specified CPU topology parameters must be greater than zero,
  78      * explicit configuration like "cpus=0" is not allowed.
  79      */
  80     if ((config->has_cpus && config->cpus == 0) ||
  81         (config->has_sockets && config->sockets == 0) ||
  82         (config->has_dies && config->dies == 0) ||
  83         (config->has_cores && config->cores == 0) ||
  84         (config->has_threads && config->threads == 0) ||
  85         (config->has_maxcpus && config->maxcpus == 0)) {
  86         warn_report("Deprecated CPU topology (considered invalid): "
  87                     "CPU topology parameters must be greater than zero");
  88     }
  89
  90     /*
  91      * If not supported by the machine, a topology parameter must be
  92      * omitted or specified equal to 1.
  93      */
  94     if (!mc->smp_props.dies_supported && dies > 1) {
  95         error_setg(errp, "dies not supported by this machine's CPU topology");
  96         return;
  97     }
  98
  99     dies = dies > 0 ? dies : 1;
 100
 101     /* compute missing values based on the provided ones */
 102     if (cpus == 0 && maxcpus == 0) {
 103         sockets = sockets > 0 ? sockets : 1;
 104         cores = cores > 0 ? cores : 1;
 105         threads = threads > 0 ? threads : 1;
 106     } else {
 107         maxcpus = maxcpus > 0 ? maxcpus : cpus;
 108
 109         if (mc->smp_props.prefer_sockets) {
 110             /* prefer sockets over cores before 6.2 */
 111             if (sockets == 0) {
 112                 cores = cores > 0 ? cores : 1;
 113                 threads = threads > 0 ? threads : 1;
 114                 sockets = maxcpus / (dies * cores * threads);
 115             } else if (cores == 0) {
 116                 threads = threads > 0 ? threads : 1;
 117                 cores = maxcpus / (sockets * dies * threads);
 118             }
 119         } else {
 120             /* prefer cores over sockets since 6.2 */
 121             if (cores == 0) {
 122                 sockets = sockets > 0 ? sockets : 1;
 123                 threads = threads > 0 ? threads : 1;
 124                 cores = maxcpus / (sockets * dies * threads);
 125             } else if (sockets == 0) {
 126                 threads = threads > 0 ? threads : 1;
 127                 sockets = maxcpus / (dies * cores * threads);
 128             }
 129         }
 130
 131         /* try to calculate omitted threads at last */
 132         if (threads == 0) {
 133             threads = maxcpus / (sockets * dies * cores);
 134         }
 135     }
 136
 137     maxcpus = maxcpus > 0 ? maxcpus : sockets * dies * cores * threads;
 138     cpus = cpus > 0 ? cpus : maxcpus;
 139
 140     ms->smp.cpus = cpus;
 141     ms->smp.sockets = sockets;
 142     ms->smp.dies = dies;
 143     ms->smp.cores = cores;
 144     ms->smp.threads = threads;
 145     ms->smp.max_cpus = maxcpus;
 146
 147     /* sanity-check of the computed topology */
 148     if (sockets * dies * cores * threads != maxcpus) {
 149         g_autofree char *topo_msg = cpu_hierarchy_to_string(ms);
 150         error_setg(errp, "Invalid CPU topology: "
 151                    "product of the hierarchy must match maxcpus: "
 152                    "%s != maxcpus (%u)",
 153                    topo_msg, maxcpus);
 154         return;
 155     }
 156
 157     if (maxcpus < cpus) {
 158         g_autofree char *topo_msg = cpu_hierarchy_to_string(ms);
 159         error_setg(errp, "Invalid CPU topology: "
 160                    "maxcpus must be equal to or greater than smp: "
 161                    "%s == maxcpus (%u) < smp_cpus (%u)",
 162                    topo_msg, maxcpus, cpus);
 163         return;
 164     }
 165
 166     if (ms->smp.cpus < mc->min_cpus) {
 167         error_setg(errp, "Invalid SMP CPUs %d. The min CPUs "
 168                    "supported by machine '%s' is %d",
 169                    ms->smp.cpus,
 170                    mc->name, mc->min_cpus);
 171         return;
 172     }
 173
 174     if (ms->smp.max_cpus > mc->max_cpus) {
 175         error_setg(errp, "Invalid SMP CPUs %d. The max CPUs "
 176                    "supported by machine '%s' is %d",
 177                    ms->smp.max_cpus,
 178                    mc->name, mc->max_cpus);
 179         return;
 180     }
 181 }