cpumask: convert struct cpuinfo_x86's llc_shared_map to cpumask_var_t

Impact: reduce kernel memory usage when CONFIG_CPUMASK_OFFSTACK=y

Signed-off-by: Rusty Russell <[e-mail]>

arch/x86/include/asm/processor.h

···
 	unsigned long		loops_per_jiffy;
 #ifdef CONFIG_SMP
 	/* cpus sharing the last level cache: */
-	cpumask_t		llc_shared_map;
+	cpumask_var_t		llc_shared_map;
 #endif
 	/* cpuid returned max cores value: */
 	u16			 x86_max_cores;

arch/x86/kernel/smpboot.c

···
 	cpu_idle();
 }
 
+#ifdef CONFIG_CPUMASK_OFFSTACK
+/* In this case, llc_shared_map is a pointer to a cpumask. */
+static inline void copy_cpuinfo_x86(struct cpuinfo_x86 *dst,
+				    const struct cpuinfo_x86 *src)
+{
+	struct cpumask *llc = dst->llc_shared_map;
+	*dst = *src;
+	dst->llc_shared_map = llc;
+}
+#else
+static inline void copy_cpuinfo_x86(struct cpuinfo_x86 *dst,
+				    const struct cpuinfo_x86 *src)
+{
+	*dst = *src;
+}
+#endif /* CONFIG_CPUMASK_OFFSTACK */
+
 /*
  * The bootstrap kernel entry code has set these up. Save them for
  * a given CPU
···
 {
 	struct cpuinfo_x86 *c = &cpu_data(id);
 
-	*c = boot_cpu_data;
+	copy_cpuinfo_x86(c, &boot_cpu_data);
 	c->cpu_index = id;
 	if (id != 0)
 		identify_secondary_cpu(c);
···
 				cpumask_set_cpu(cpu, cpu_sibling_mask(i));
 				cpumask_set_cpu(i, cpu_core_mask(cpu));
 				cpumask_set_cpu(cpu, cpu_core_mask(i));
-				cpumask_set_cpu(i, &c->llc_shared_map);
-				cpumask_set_cpu(cpu, &o->llc_shared_map);
+				cpumask_set_cpu(i, c->llc_shared_map);
+				cpumask_set_cpu(cpu, o->llc_shared_map);
 			}
 		}
 	} else {
 		cpumask_set_cpu(cpu, cpu_sibling_mask(cpu));
 	}
 
-	cpumask_set_cpu(cpu, &c->llc_shared_map);
+	cpumask_set_cpu(cpu, c->llc_shared_map);
 
 	if (current_cpu_data.x86_max_cores == 1) {
 		cpumask_copy(cpu_core_mask(cpu), cpu_sibling_mask(cpu));
···
 	for_each_cpu(i, cpu_sibling_setup_mask) {
 		if (per_cpu(cpu_llc_id, cpu) != BAD_APICID &&
 		    per_cpu(cpu_llc_id, cpu) == per_cpu(cpu_llc_id, i)) {
-			cpumask_set_cpu(i, &c->llc_shared_map);
-			cpumask_set_cpu(cpu, &cpu_data(i).llc_shared_map);
+			cpumask_set_cpu(i, c->llc_shared_map);
+			cpumask_set_cpu(cpu, cpu_data(i).llc_shared_map);
 		}
 		if (c->phys_proc_id == cpu_data(i).phys_proc_id) {
 			cpumask_set_cpu(i, cpu_core_mask(cpu));
···
 	if (sched_mc_power_savings || sched_smt_power_savings)
 		return cpu_core_mask(cpu);
 	else
-		return &c->llc_shared_map;
+		return c->llc_shared_map;
 }
 
 static void impress_friends(void)
···
 	for_each_possible_cpu(i) {
 		alloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
 		alloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
+		alloc_cpumask_var(&cpu_data(i).llc_shared_map, GFP_KERNEL);
 		cpumask_clear(per_cpu(cpu_core_map, i));
 		cpumask_clear(per_cpu(cpu_sibling_map, i));
+		cpumask_clear(cpu_data(i).llc_shared_map);
 	}
 	set_cpu_sibling_map(0);