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

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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: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Huacai Chen 2024-07-20 22:40:58 +08:00
parent 7697a0fe01
commit 12d3b559b8
3 changed files with 22 additions and 11 deletions
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22
arch/loongarch/kernel/acpi.c
View File

@ -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;
}

4
arch/loongarch/kernel/setup.c
View File

@ -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);
}

7
arch/loongarch/kernel/smp.c
View File

@ -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);