linux/cpukinds: add Intel "LowPower" PMU set

Linux commit 9f4a39757c81d532f64232702537c53ad4092a5e added a new
PMU set of core called "lowpower":
"The upcoming ARL-H hybrid processor contains 2 different atom uarchs
 which have different PMU capabilities."

It's not totally clear to me if previous generations with LP-Ecore
(meteor and lunar lake) have different Ecore uarch, but they don't
expose different PMU sets anyway (but we are able to distinguish them
thanks to frequencies).

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>

doc/hwloc.doxy

@@ -2473,7 +2473,7 @@ as reported by some <tt>cpufreq</tt> or ACPI drivers on Linux
 </dd>
 <dt>CoreType (x86)</dt>
 <dd>A string describing the kind of core,
-currently <tt>IntelAtom</tt> or <tt>IntelCore</tt>,
+currently <tt>IntelAtom</tt>, <tt>IntelCore</tt> or <tt>IntelLowPower</tt>,
 as reported by the x86 CPUID instruction and Linux PMU on some Intel processors.
 </dd>
 <dt>LinuxCapacity (Linux)</dt>

hwloc/topology-linux.c

@@ -4722,7 +4722,7 @@ look_sysfscpukinds(struct hwloc_topology *topology,
   int max_without_basefreq = 0; /* any cpu where we have maxfreq without basefreq? */
   char str[293];
   char *env;
-  hwloc_bitmap_t atom_pmu_set, core_pmu_set;
+  hwloc_bitmap_t atom_pmu_set, core_pmu_set, lowp_pmu_set;
   int maxfreq_enabled = -1; /* -1 means adjust (default), 0 means ignore, 1 means enforce */
   int use_cppc_nominal_freq = -1; /* -1 means try, 0 no, 1 yes */
   unsigned adjust_max = 10;
@@ -4842,6 +4842,7 @@ look_sysfscpukinds(struct hwloc_topology *topology,
   /* look at Intel core/atom PMUs */
   atom_pmu_set = hwloc__alloc_read_path_as_cpulist("/sys/devices/cpu_atom/cpus", data->root_fd);
   core_pmu_set = hwloc__alloc_read_path_as_cpulist("/sys/devices/cpu_core/cpus", data->root_fd);
+  lowp_pmu_set = hwloc__alloc_read_path_as_cpulist("/sys/devices/cpu_lowpower/cpus", data->root_fd);
   if (atom_pmu_set) {
     hwloc_linux_cpukinds_register_one(topology, atom_pmu_set,
                                       HWLOC_CPUKIND_EFFICIENCY_UNKNOWN,
@@ -4858,6 +4859,14 @@ look_sysfscpukinds(struct hwloc_topology *topology,
   } else {
     hwloc_bitmap_free(core_pmu_set);
   }
+  if (lowp_pmu_set) {
+    hwloc_linux_cpukinds_register_one(topology, lowp_pmu_set,
+                                      HWLOC_CPUKIND_EFFICIENCY_UNKNOWN,
+                                      (char *) "CoreType", (char *) "IntelLowPower");
+    /* the cpuset is given to the callee */
+  } else {
+    hwloc_bitmap_free(lowp_pmu_set);
+  }
 
   return 0;
 }