[PATCH 13/16] arm64: mm: introduce __per_cpu_local_off

[Yang Shi <yang@os.amperecomputing.com>]

this_cpu_*() ops will use it to get the local percpu address.  It has
the same value for all CPUs.

Also introduce pcpu_local_base, which is the base address of local
percpu map.

Signed-off-by: Yang Shi <yang@os.amperecomputing.com>
---
 arch/arm64/kernel/smp.c | 4 ++++
 include/linux/percpu.h  | 2 ++
 mm/percpu.c             | 3 +++
 3 files changed, 9 insertions(+)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 4c112bab8356..4a811379c191 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -839,6 +839,9 @@ int early_cpu_to_node(int cpu)
 #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly;
 EXPORT_SYMBOL(__per_cpu_offset);
+/* Used to calculate pcpu local address, the offset is same for all CPUs */
+unsigned long __per_cpu_local_off __ro_after_init;
+EXPORT_SYMBOL(__per_cpu_local_off);
 
 void __init setup_per_cpu_areas(void)
 {
@@ -856,6 +859,7 @@ void __init setup_per_cpu_areas(void)
 	delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
 	for_each_possible_cpu(cpu)
 		__per_cpu_offset[cpu] = delta + pcpu_unit_offsets[cpu];
+	__per_cpu_local_off = (unsigned long)pcpu_local_base - (unsigned long)__per_cpu_start;
 }
 #endif
 
diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index 2f0e190aca29..5a27031dff1a 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -75,6 +75,8 @@
 
 extern void *pcpu_base_addr;
 extern const unsigned long *pcpu_unit_offsets;
+/* percpu local mapping base */
+extern void *pcpu_local_base;
 
 struct pcpu_group_info {
 	int			nr_units;	/* aligned # of units */
diff --git a/mm/percpu.c b/mm/percpu.c
index 15303611ecaf..8b273ed8e5a8 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -145,6 +145,8 @@ static unsigned int pcpu_high_unit_cpu __ro_after_init;
 
 /* the address of the first chunk which starts with the kernel static area */
 void *pcpu_base_addr __ro_after_init;
+/* The address of the first chunk local mapping */
+void *pcpu_local_base __ro_after_init;
 
 static const int *pcpu_unit_map __ro_after_init;		/* cpu -> unit */
 const unsigned long *pcpu_unit_offsets __ro_after_init;	/* cpu -> unit offset */
@@ -3305,6 +3307,7 @@ int __init pcpu_page_first_chunk(size_t reserved_size, pcpu_fc_cpu_to_node_fn_t
 		ai->reserved_size, ai->dyn_size);
 
 	pcpu_setup_first_chunk(ai, vm.addr, pcpu_vm.addr);
+	pcpu_local_base = pcpu_vm.addr;
 	goto out_free_ar;
 
 enomem:
-- 
2.47.0