[PATCH v9 17/19] arm64: Kconfig: Enable hotplug CPU on arm64 if ACPI_PROCESSOR is enabled.

Jonathan Cameron
2024-04-30T14:33:22Z

In order to move arch_register_cpu() to be called via the same path
for initially present CPUs described by ACPI and hotplugged CPUs
ACPI_HOTPLUG_CPU needs to be enabled.

The protection against invalid IDs in acpi_map_cpu() is needed as
at least one production BIOS is in the wild which reports entries
in DSDT (with no _STA method, so assumed enabled and present)
that don't match MADT.

Tested-by: Miguel Luis <miguel.luis@oracle.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

---
V9: No change.

---
arch/arm64/Kconfig | 1 +
arch/arm64/kernel/acpi.c | 22 ++++++++++++++++++++++
2 files changed, 23 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b11c98b3e84..fed7d0d54179 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -5,6 +5,7 @@ config ARM64
select ACPI_CCA_REQUIRED if ACPI
select ACPI_GENERIC_GSI if ACPI
select ACPI_GTDT if ACPI
+ select ACPI_HOTPLUG_CPU if ACPI_PROCESSOR
select ACPI_IORT if ACPI
select ACPI_REDUCED_HARDWARE_ONLY if ACPI
select ACPI_MCFG if (ACPI && PCI)
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index dba8fcec7f33..fb9368197c74 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -29,6 +29,7 @@
#include <linux/pgtable.h>

#include <acpi/ghes.h>
+#include <acpi/processor.h>
#include <asm/cputype.h>
#include <asm/cpu_ops.h>
#include <asm/daifflags.h>
@@ -413,6 +414,27 @@ void arch_reserve_mem_area(acpi_physical_address addr, size_t size)
memblock_mark_nomap(addr, size);
}

+#ifdef CONFIG_ACPI_HOTPLUG_CPU
+int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, u32 apci_id,
+ int *pcpu)
+{
+ /* If an error code is passed in this stub can't fix it */
+ if (*pcpu < 0) {
+ pr_warn_once("Unable to map CPU to valid ID\n");
+ return *pcpu;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL(acpi_map_cpu);
+
+int acpi_unmap_cpu(int cpu)
+{
+ return 0;
+}
+EXPORT_SYMBOL(acpi_unmap_cpu);
+#endif /* CONFIG_ACPI_HOTPLUG_CPU */
+
#ifdef CONFIG_ACPI_FFH
/*
* Implements ARM64 specific callbacks to support ACPI FFH Operation Region as
--
2.39.2