Commit 12d3b559 authored by Huacai Chen's avatar Huacai Chen
Browse files

LoongArch: Always enumerate MADT and setup logical-physical CPU mapping 



Some drivers want to use cpu_logical_map(), early_cpu_to_node() and some
other CPU mapping APIs, even if we use "nr_cpus=1" to hard limit the CPU
number. This is strongly required for the multi-bridges machines.

Currently, we stop parsing the MADT if the nr_cpus limit is reached, but
to achieve the above goal we should always enumerate the MADT table and
setup logical-physical CPU mapping whether there is a nr_cpus limit.

Rework the MADT enumeration:

1. Define a flag "cpu_enumerated" to distinguish the first enumeration
   (cpu_enumerated=0) and the physical hotplug case (cpu_enumerated=1)
   for set_processor_mask().

2. If cpu_enumerated=0, stop parsing only when NR_CPUS limit is reached,
   so we can setup logical-physical CPU mapping; if cpu_enumerated=1,
   stop parsing when nr_cpu_ids limit is reached, so we can avoid some
   runtime bugs. Once logical-physical CPU mapping is setup, we will let
   cpu_enumerated=1.

3. Use find_first_zero_bit() instead of cpumask_next_zero() to find the
   next zero bit (free logical CPU id) in the cpu_present_mask, because
   cpumask_next_zero() will stop at nr_cpu_ids.

4. Only touch cpu_possible_mask if cpu_enumerated=0, this is in order to
   avoid some potential crashes, because cpu_possible_mask is marked as
   __ro_after_init.

5. In prefill_possible_map(), clear cpu_present_mask bits greater than
   nr_cpu_ids, in order to avoid a CPU be "present" but not "possible".

Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 7697a0fe

arch/loongarch/kernel/acpi.c

+16 −6
Original line number Diff line number Diff line
@@ -57,15 +57,22 @@ void __iomem *acpi_os_ioremap(acpi_physical_address phys, acpi_size size) 
		return ioremap_cache(phys, size);

}



static int cpu_enumerated = 0;



#ifdef CONFIG_SMP

static int set_processor_mask(u32 id, u32 flags)

{



	int nr_cpus;

	int cpu, cpuid = id;



	if (num_processors >= nr_cpu_ids) {

		pr_warn(PREFIX "nr_cpus/possible_cpus limit of %i reached."

			" processor 0x%x ignored.\n", nr_cpu_ids, cpuid);

	if (!cpu_enumerated)

		nr_cpus = NR_CPUS;

	else

		nr_cpus = nr_cpu_ids;



	if (num_processors >= nr_cpus) {

		pr_warn(PREFIX "nr_cpus limit of %i reached."

			" processor 0x%x ignored.\n", nr_cpus, cpuid);



		return -ENODEV;
@@ -73,11 +80,13 @@ static int set_processor_mask(u32 id, u32 flags) 
	if (cpuid == loongson_sysconf.boot_cpu_id)

		cpu = 0;

	else

		cpu = cpumask_next_zero(-1, cpu_present_mask);

		cpu = find_first_zero_bit(cpumask_bits(cpu_present_mask), NR_CPUS);



	if (!cpu_enumerated)

		set_cpu_possible(cpu, true);



	if (flags & ACPI_MADT_ENABLED) {

		num_processors++;

		set_cpu_possible(cpu, true);

		set_cpu_present(cpu, true);

		__cpu_number_map[cpuid] = cpu;

		__cpu_logical_map[cpu] = cpuid;
@@ -138,6 +147,7 @@ static void __init acpi_process_madt(void) 
	acpi_table_parse_madt(ACPI_MADT_TYPE_EIO_PIC,

			acpi_parse_eio_master, MAX_IO_PICS);



	cpu_enumerated = 1;

	loongson_sysconf.nr_cpus = num_processors;

}

arch/loongarch/kernel/setup.c

+3 −1
Original line number Diff line number Diff line
@@ -576,8 +576,10 @@ static void __init prefill_possible_map(void) 


	for (i = 0; i < possible; i++)

		set_cpu_possible(i, true);

	for (; i < NR_CPUS; i++)

	for (; i < NR_CPUS; i++) {

		set_cpu_present(i, false);

		set_cpu_possible(i, false);

	}



	set_nr_cpu_ids(possible);

}

arch/loongarch/kernel/smp.c

+3 −4
Original line number Diff line number Diff line
@@ -271,11 +271,10 @@ static void __init fdt_smp_setup(void) 
		if (cpuid >= nr_cpu_ids)

			continue;



		if (cpuid == loongson_sysconf.boot_cpu_id) {

		if (cpuid == loongson_sysconf.boot_cpu_id)

			cpu = 0;

		} else {

			cpu = cpumask_next_zero(-1, cpu_present_mask);

		}

		else

			cpu = find_first_zero_bit(cpumask_bits(cpu_present_mask), NR_CPUS);



		num_processors++;

		set_cpu_possible(cpu, true);