[patch V4 21/41] x86/cpu/topology: Cure the abuse of cpuinfo for persisting logical ids

[Thomas Gleixner]

Per CPU cpuinfo is used to persist the logical package and die IDs. That's
really not the right place simply because cpuinfo is subject to be
reinitialized when a CPU goes through an offline/online cycle.

This works by chance today, but that's far from correct and neither obvious
nor documented.

Add a per cpu datastructure which persists those logical IDs, which allows
to cleanup the CPUID evaluation code.

This is a temporary workaround until the larger topology management is in
place, which makes all of this logical management mechanics obsolete.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Juergen Gross <jgross@xxxxxxxx>
Tested-by: Sohil Mehta <sohil.mehta@xxxxxxxxx>
Tested-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>

---
 arch/x86/kernel/smpboot.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -124,7 +124,20 @@ struct mwait_cpu_dead {
  */
 static DEFINE_PER_CPU_ALIGNED(struct mwait_cpu_dead, mwait_cpu_dead);
 
-/* Logical package management. We might want to allocate that dynamically */
+/* Logical package management. */
+struct logical_maps {
+	u32	phys_pkg_id;
+	u32	phys_die_id;
+	u32	logical_pkg_id;
+	u32	logical_die_id;
+};
+
+/* Temporary workaround until the full topology mechanics is in place */
+static DEFINE_PER_CPU_READ_MOSTLY(struct logical_maps, logical_maps) = {
+	.phys_pkg_id	= U32_MAX,
+	.phys_die_id	= U32_MAX,
+};
+
 unsigned int __max_logical_packages __read_mostly;
 EXPORT_SYMBOL(__max_logical_packages);
 static unsigned int logical_packages __read_mostly;
@@ -345,10 +358,8 @@ int topology_phys_to_logical_pkg(unsigne
 	int cpu;
 
 	for_each_possible_cpu(cpu) {
-		struct cpuinfo_x86 *c = &cpu_data(cpu);
-
-		if (c->initialized && c->topo.pkg_id == phys_pkg)
-			return c->topo.logical_pkg_id;
+		if (per_cpu(logical_maps.phys_pkg_id, cpu) == phys_pkg)
+			return per_cpu(logical_maps.logical_pkg_id, cpu);
 	}
 	return -1;
 }
@@ -366,11 +377,9 @@ static int topology_phys_to_logical_die(
 	int cpu, proc_id = cpu_data(cur_cpu).topo.pkg_id;
 
 	for_each_possible_cpu(cpu) {
-		struct cpuinfo_x86 *c = &cpu_data(cpu);
-
-		if (c->initialized && c->topo.die_id == die_id &&
-		    c->topo.pkg_id == proc_id)
-			return c->topo.logical_die_id;
+		if (per_cpu(logical_maps.phys_pkg_id, cpu) == proc_id &&
+		    per_cpu(logical_maps.phys_die_id, cpu) == die_id)
+			return per_cpu(logical_maps.logical_die_id, cpu);
 	}
 	return -1;
 }
@@ -395,6 +404,8 @@ int topology_update_package_map(unsigned
 			cpu, pkg, new);
 	}
 found:
+	per_cpu(logical_maps.phys_pkg_id, cpu) = pkg;
+	per_cpu(logical_maps.logical_pkg_id, cpu) = new;
 	cpu_data(cpu).topo.logical_pkg_id = new;
 	return 0;
 }
@@ -418,6 +429,8 @@ int topology_update_die_map(unsigned int
 			cpu, die, new);
 	}
 found:
+	per_cpu(logical_maps.phys_die_id, cpu) = die;
+	per_cpu(logical_maps.logical_die_id, cpu) = new;
 	cpu_data(cpu).topo.logical_die_id = new;
 	return 0;
 }