x86/cpu: Add get_llc_id() helper function

Factor out a helper function rather than export cpu_llc_id, which is
needed in order to be able to build the AMD uncore driver as a module.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210817221048.88063-7-kim.phillips@amd.com

arch/x86/events/amd/uncore.c

@@ -452,7 +452,7 @@ static int amd_uncore_cpu_starting(unsigned int cpu)
 
 	if (amd_uncore_llc) {
 		uncore = *per_cpu_ptr(amd_uncore_llc, cpu);
-		uncore->id = per_cpu(cpu_llc_id, cpu);
+		uncore->id = get_llc_id(cpu);
 
 		uncore = amd_uncore_find_online_sibling(uncore, amd_uncore_llc);
 		*per_cpu_ptr(amd_uncore_llc, cpu) = uncore;

arch/x86/include/asm/processor.h

@@ -795,6 +795,8 @@ extern int set_tsc_mode(unsigned int val);
 
 DECLARE_PER_CPU(u64, msr_misc_features_shadow);
 
+extern u16 get_llc_id(unsigned int cpu);
+
 #ifdef CONFIG_CPU_SUP_AMD
 extern u32 amd_get_nodes_per_socket(void);
 extern u32 amd_get_highest_perf(void);

arch/x86/kernel/cpu/amd.c

@@ -438,7 +438,7 @@ static void srat_detect_node(struct cpuinfo_x86 *c)
 
 	node = numa_cpu_node(cpu);
 	if (node == NUMA_NO_NODE)
-		node = per_cpu(cpu_llc_id, cpu);
+		node = get_llc_id(cpu);
 
 	/*
 	 * On multi-fabric platform (e.g. Numascale NumaChip) a

arch/x86/kernel/cpu/common.c

@@ -79,6 +79,12 @@ EXPORT_SYMBOL(smp_num_siblings);
 /* Last level cache ID of each logical CPU */
 DEFINE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id) = BAD_APICID;
 
+u16 get_llc_id(unsigned int cpu)
+{
+	return per_cpu(cpu_llc_id, cpu);
+}
+EXPORT_SYMBOL_GPL(get_llc_id);
+
 /* correctly size the local cpu masks */
 void __init setup_cpu_local_masks(void)
 {