[PATCH v6 06/16] ACPI: processor: Register deferred CPUs from acpi_processor_get_info()

[Jonathan Cameron]

From: James Morse <james.morse at arm.com>

The arm64 specific arch_register_cpu() call may defer CPU registration
until the ACPI interpreter is available and the _STA method can
be evaluated.

If this occurs, then a second attempt is made in
acpi_processor_get_info(). Note that the arm64 specific call has
not yet been added so for now this will be called for the original
hotplug case.

For architectures that do not defer until the ACPI Processor
driver loads (e.g. x86), for initially present CPUs there will
already be a CPU device. If present do not try to register again.

Systems can still be booted with 'acpi=off', or not include an
ACPI description at all as in these cases arch_register_cpu()
will not have deferred registration when first called.

This moves the CPU register logic back to a subsys_initcall(),
while the memory nodes will have been registered earlier.
Note this is where the call was prior to the cleanup series so
there should be no side effects of moving it back again for this
specific case.

[PATCH 00/21] Initial cleanups for vCPU HP.
https://lore.kernel.org/all/ZVyz%2FVe5pPu8AWoA@shell.armlinux.org.uk/

e.g. 5b95f94c3b9f ("x86/topology: Switch over to GENERIC_CPU_DEVICES")

Signed-off-by: James Morse <james.morse at arm.com>
Reviewed-by: Gavin Shan <gshan at redhat.com>
Tested-by: Miguel Luis <miguel.luis at oracle.com>
Tested-by: Vishnu Pajjuri <vishnu at os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu at arm.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel at armlinux.org.uk>
Co-developed-by: Jonathan Cameron <Jonathan.Cameron at huawei.com>
Signed-off-by: Joanthan Cameron <Jonathan.Cameron at huawei.com>
---
v6: Squash the two paths for conventional CPU Hotplug and arm64
    vCPU HP.
v5: Update commit message to make it clear this is moving the
    init back to where it was until very recently.

    No longer change the condition in the earlier registration point
    as that will be handled by the arm64 registration routine
    deferring until called again here.
---
 drivers/acpi/acpi_processor.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index 7ecb13775d7f..0cac77961020 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -356,8 +356,18 @@ static int acpi_processor_get_info(struct acpi_device *device)
 	 *
 	 *  NOTE: Even if the processor has a cpuid, it may not be present
 	 *  because cpuid <-> apicid mapping is persistent now.
+	 *
+	 *  Note this allows 3 flows, it is up to the arch_register_cpu()
+	 *  call to reject any that are not supported on a given architecture.
+	 *  A) CPU becomes present.
+	 *  B) Previously invalid logical CPU ID (Same as becoming present)
+	 *  C) CPU already present and now being enabled (and wasn't registered
+	 *     early on an arch that doesn't defer to here)
 	 */
-	if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id)) {
+	if ((!invalid_logical_cpuid(pr->id) && cpu_present(pr->id) &&
+	     !get_cpu_device(pr->id)) ||
+	    invalid_logical_cpuid(pr->id) ||
+	    !cpu_present(pr->id)) {
 		ret = acpi_processor_hotadd_init(pr, device);
 
 		if (ret)
-- 
2.39.2