[PATCH 5.11 120/120] x86/apic/of: Fix CPU devicetree-node lookups

From: Greg Kroah-Hartman
Date: Mon Mar 22 2021 - 08:39:47 EST

From: Johan Hovold <johan@xxxxxxxxxx>

commit dd926880da8dbbe409e709c1d3c1620729a94732 upstream.

Architectures that describe the CPU topology in devicetree and do not have
an identity mapping between physical and logical CPU ids must override the
default implementation of arch_match_cpu_phys_id().

Failing to do so breaks CPU devicetree-node lookups using of_get_cpu_node()
and of_cpu_device_node_get() which several drivers rely on. It also causes
the CPU struct devices exported through sysfs to point to the wrong
devicetree nodes.

On x86, CPUs are described in devicetree using their APIC ids and those
do not generally coincide with the logical ids, even if CPU0 typically
uses APIC id 0.

Add the missing implementation of arch_match_cpu_phys_id() so that CPU-node
lookups work also with SMP.

Apart from fixing the broken sysfs devicetree-node links this likely does
not affect current users of mainline kernels on x86.

Fixes: 4e07db9c8db8 ("x86/devicetree: Use CPU description from Device Tree")
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210312092033.26317-1-johan@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
arch/x86/kernel/apic/apic.c | 5 +++++
1 file changed, 5 insertions(+)

--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -2334,6 +2334,11 @@ static int cpuid_to_apicid[] = {
[0 ... NR_CPUS - 1] = -1,

+bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
+ return phys_id == cpuid_to_apicid[cpu];
* apic_id_is_primary_thread - Check whether APIC ID belongs to a primary thread