ACPI: CPPC: Perform fast check switch only for online CPUs

per_cpu(cpc_desc_ptr, cpu) object is initialized for only the online
CPUs via acpi_soft_cpu_online() --> __acpi_processor_start() -->
acpi_cppc_processor_probe().

However the function cppc_allow_fast_switch() checks for the validity
of the _CPC object for all the present CPUs. This breaks when the
kernel is booted with "nosmt=force".

Check fast_switch capability only on online CPUs

Fixes: 15eece6 ("ACPI: CPPC: Fix NULL pointer dereference when nosmp is used")
Reviewed-by: "Mario Limonciello (AMD) (kernel.org)" <[email protected]>
Signed-off-by: Gautham R. Shenoy <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: gautshen

drivers/acpi/cppc_acpi.c

@@ -476,7 +476,7 @@ bool cppc_allow_fast_switch(void)
 	struct cpc_desc *cpc_ptr;
 	int cpu;
 
-	for_each_present_cpu(cpu) {
+	for_each_online_cpu(cpu) {
 		cpc_ptr = per_cpu(cpc_desc_ptr, cpu);
 		desired_reg = &cpc_ptr->cpc_regs[DESIRED_PERF];
 		if (!CPC_IN_SYSTEM_MEMORY(desired_reg) &&