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Commit 133b9731 authored by Yadu MG's avatar Yadu MG Committed by Gerrit - the friendly Code Review server
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arm64: Allow boot on cpus other than logical cpu 0 



Kernel assumes boot cpu to be always on logical cpu 0.
At times there are benefits to boot kernel on other cpus
as well. On a heterogeneous multiprocessor system, booting
on a high-performance core can improve the boot time.

This patch removes the assumption that boot-cpu is logical
cpu 0. Device tree is looked up very early in boot to
determine the boot-cpus logical id. It also fixes hard-coding
of logical cpu 0 done at various places.

Change-Id: I27f1b2762db23a0af84fa5289f4b68ed31d84560
Signed-off-by: default avatarYadu MG <ymg@codeaurora.org>
parent 8136c468

arch/arm64/include/asm/cpu_ops.h

+2 −1
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 


#include <linux/init.h>

#include <linux/threads.h>

#include <linux/cpu.h>



/**

 * struct cpu_operations - Callback operations for hotplugging CPUs.
@@ -68,7 +69,7 @@ int __init cpu_read_ops(int cpu); 


static inline void __init cpu_read_bootcpu_ops(void)

{

	cpu_read_ops(0);

	cpu_read_ops(logical_bootcpu_id);

}



#endif /* ifndef __ASM_CPU_OPS_H */

arch/arm64/kernel/cpu_ops.c

+1 −1
Original line number Diff line number Diff line
@@ -81,7 +81,7 @@ static const char *__init cpu_read_enable_method(int cpu) 
			 * when spin-table is used for secondaries).

			 * Don't warn spuriously.

			 */

			if (cpu != 0)

			if (cpu != logical_bootcpu_id)

				pr_err("%pOF: missing enable-method property\n",

					dn);

		}

arch/arm64/kernel/cpuinfo.c

+1 −1
Original line number Diff line number Diff line
@@ -387,7 +387,7 @@ void cpuinfo_store_cpu(void) 


void __init cpuinfo_store_boot_cpu(void)

{

	struct cpuinfo_arm64 *info = &per_cpu(cpu_data, 0);

	struct cpuinfo_arm64 *info = &per_cpu(cpu_data, logical_bootcpu_id);

	__cpuinfo_store_cpu(info);



	boot_cpu_data = *info;

arch/arm64/kernel/setup.c

+87 −1
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#include <linux/psci.h>

#include <linux/sched/task.h>

#include <linux/mm.h>

#include <linux/libfdt.h>



#include <asm/acpi.h>

#include <asm/fixmap.h>
@@ -99,10 +100,93 @@ static struct resource mem_res[] = { 
 */

u64 __cacheline_aligned boot_args[4];



unsigned int logical_bootcpu_id __read_mostly;

EXPORT_SYMBOL(logical_bootcpu_id);



extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size,

				       pgprot_t prot);

/*

 * Parse the device tree cpu nodes and enumerate logical cpu number for

 * the boot cpu based on the mpidr value and reg value from the cpu node.

 * If the parsing fails at any point, value 0 will be returned which make

 * sure, we fallback to the default kernel behavior.

 */

static unsigned int __init parse_logical_bootcpu(u64 dt_phys)

{

	void *fdt;

	int size, parent, node, len;

	unsigned int logical_cpu_id = 0;

	fdt64_t *prop;

	u64 mpidr, hwid;



	/*

	 * Try to map the FDT early. If this fails, we simply bail,

	 * and proceed with logical cpu as 0. We will make another

	 * attempt at mapping the FDT in setup_machine()

	 */

	early_fixmap_init();

	fdt = __fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);

	if (!fdt)

		return 0;



	mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;



	parent = fdt_path_offset(fdt, "/cpus");

	if (parent < 0)

		return 0;

	/*

	 * Like of_parse_and_init_cpus(), we assume that the device tree

	 * entries for the dt nodes are defined in ascending order for

	 * populating cpu logical map.

	 */

	fdt_for_each_subnode(node, fdt, parent) {

		prop = fdt_getprop_w(fdt, node, "reg", &len);

		if (!prop || len != sizeof(u64))

			return 0;



		hwid = fdt64_to_cpu(*prop);

		if (hwid & ~MPIDR_HWID_BITMASK)

			return 0;



		/*

		 * If the cpu node reg value matches the currently active

		 * processor(boot cpu), we bail out from the loop.

		 */

		if (hwid == mpidr)

			return logical_cpu_id;



		logical_cpu_id++;



		if (logical_cpu_id >= NR_CPUS)

			return 0;

	}



	return 0;

}



DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);



/*

 * smp_processor_id() returns the current processor number which

 * internally uses per-cpu variable cpu_number. At this stage,

 * since per-cpu area is still not initialized and the kernel

 * cannot assume current processor number to be 0. This function

 * temporarily assigns the current processor to be logical_bootcpu_id,

 * which is essentially enumerated from the device tree. In later stages

 * of boot the appropriate values for cpu_number will be assigned with

 * the call to smp_prepare_cpus().

 */

static inline void fix_smp_processor_id(void)

{

	per_cpu(cpu_number, 0) = logical_bootcpu_id;

}



void __init smp_setup_processor_id(void)

{

	u64 mpidr = read_cpuid_mpidr() & MPIDR_HWID_BITMASK;

	cpu_logical_map(0) = mpidr;

	logical_bootcpu_id = parse_logical_bootcpu(__fdt_pointer);



	cpu_logical_map(logical_bootcpu_id) = mpidr;



	/*

	 * clear __my_cpu_offset on boot CPU to avoid hang caused by
@@ -111,6 +195,8 @@ void __init smp_setup_processor_id(void) 
	 */

	set_my_cpu_offset(0);

	pr_info("Booting Linux on physical CPU 0x%lx\n", (unsigned long)mpidr);



	fix_smp_processor_id();

}



bool arch_match_cpu_phys_id(int cpu, u64 phys_id)

arch/arm64/kernel/smp.c

+24 −19
Original line number Diff line number Diff line
@@ -461,9 +461,12 @@ static bool __init is_mpidr_duplicate(unsigned int cpu, u64 hwid) 
{

	unsigned int i;



	for (i = 1; (i < cpu) && (i < NR_CPUS); i++)

	for (i = 0; (i <= cpu) && (i < NR_CPUS); i++) {

		if (i == logical_bootcpu_id)

			continue;

		if (cpu_logical_map(i) == hwid)

			return true;

	}

	return false;

}
@@ -485,7 +488,7 @@ static int __init smp_cpu_setup(int cpu) 
}



static bool bootcpu_valid __initdata;

static unsigned int cpu_count = 1;

static unsigned int cpu_count;



#ifdef CONFIG_ACPI

static struct acpi_madt_generic_interrupt cpu_madt_gicc[NR_CPUS];
@@ -522,7 +525,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor) 
	}



	/* Check if GICC structure of boot CPU is available in the MADT */

	if (cpu_logical_map(0) == hwid) {

	if (cpu_logical_map(logical_bootcpu_id) == hwid) {

		if (bootcpu_valid) {

			pr_err("duplicate boot CPU MPIDR: 0x%llx in MADT\n",

			       hwid);
@@ -530,7 +533,8 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor) 
		}

		bootcpu_valid = true;

		cpu_madt_gicc[0] = *processor;

		early_map_cpu_to_node(0, acpi_numa_get_nid(0, hwid));

		early_map_cpu_to_node(logical_bootcpu_id,

					acpi_numa_get_nid(0, hwid));

		return;

	}
@@ -583,7 +587,8 @@ DEFINE_PER_CPU(bool, pending_ipi); 
/*

 * Enumerate the possible CPU set from the device tree and build the

 * cpu logical map array containing MPIDR values related to logical

 * cpus. Assumes that cpu_logical_map(0) has already been initialized.

 * cpus. Assumes that cpu_logical_map(logical_bootcpu_id) has already

 * been initialized.

 */

static void __init of_parse_and_init_cpus(void)

{
@@ -601,13 +606,7 @@ static void __init of_parse_and_init_cpus(void) 
			goto next;

		}



		/*

		 * The numbering scheme requires that the boot CPU

		 * must be assigned logical id 0. Record it so that

		 * the logical map built from DT is validated and can

		 * be used.

		 */

		if (hwid == cpu_logical_map(0)) {

		if (hwid == cpu_logical_map(logical_bootcpu_id)) {

			if (bootcpu_valid) {

				pr_err("%pOF: duplicate boot cpu reg property in DT\n",

					dn);
@@ -615,15 +614,17 @@ static void __init of_parse_and_init_cpus(void) 
			}



			bootcpu_valid = true;

			early_map_cpu_to_node(0, of_node_to_nid(dn));

			early_map_cpu_to_node(logical_bootcpu_id,

						of_node_to_nid(dn));



			/*

			 * cpu_logical_map has already been

			 * initialized and the boot cpu doesn't need

			 * the enable-method so continue without

			 * incrementing cpu.

			 * boot cpu's cpu_logical_map is already

			 * initialized and the boot cpu doesn't need the

			 * enable-method like secondary cpu's. Now, as we

			 * can't assume logical boot cpu to be 0, we need

			 * to loop through entire logical cpu map.

			 */

			continue;

			goto next;

		}



		if (cpu_count >= NR_CPUS)
@@ -674,8 +675,12 @@ void __init smp_init_cpus(void) 
	 * with entries in cpu_logical_map while initializing the cpus.

	 * If the cpu set-up fails, invalidate the cpu_logical_map entry.

	 */

	for (i = 1; i < nr_cpu_ids; i++) {

	for (i = 0; i < nr_cpu_ids; i++) {

		if (cpu_logical_map(i) != INVALID_HWID) {

			if (cpu_logical_map(i) ==

					cpu_logical_map(logical_bootcpu_id))

				continue;



			if (smp_cpu_setup(i))

				cpu_logical_map(i) = INVALID_HWID;

		}