On 2019/5/4 7:24, Jeremy Linton wrote:
> ACPI 6.3 adds a flag to indicate that child nodes are all
> identical cores. This is useful to authoritatively determine
> if a set of (possibly offline) cores are identical or not.
>
> Since the flag doesn't give us a unique id we can generate
> one and use it to create bitmaps of sibling nodes, or simply
> in a loop to determine if a subset of cores are identical.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> ---
> drivers/acpi/pptt.c | 26 ++++++++++++++++++++++++++
> include/linux/acpi.h | 5 +++++
> 2 files changed, 31 insertions(+)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index 83a026765faa..1865515297ca 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -660,3 +660,29 @@ int find_acpi_cpu_topology_package(unsigned int cpu)
> return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
> ACPI_PPTT_PHYSICAL_PACKAGE);
> }
> +
> +/**
> + * find_acpi_cpu_topology_hetero_id() - Get a core architecture tag
> + * @cpu: Kernel logical CPU number
> + *
> + * Determine a unique heterogeneous tag for the given CPU. CPUs with the same
> + * implementation should have matching tags.
> + *
> + * The returned tag can be used to group peers with identical implementation.
> + *
> + * The search terminates when a level is found with the identical implementation
> + * flag set or we reach a root node.
> + *
> + * Due to limitations in the PPTT data structure, there may be rare situations
> + * where two cores in a heterogeneous machine may be identical, but won't have
> + * the same tag.
> + *
> + * Return: -ENOENT if the PPTT doesn't exist, or the CPU cannot be found.
> + * Otherwise returns a value which represents a group of identical cores
> + * similar to this CPU.
> + */
> +int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
> +{
> + return find_acpi_cpu_topology_tag(cpu, PPTT_ABORT_PACKAGE,
> + ACPI_PPTT_ACPI_IDENTICAL);
> +}
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index d5dcebd7aad3..1444fb042898 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1309,6 +1309,7 @@ static inline int lpit_read_residency_count_address(u64 *address)
> #ifdef CONFIG_ACPI_PPTT
> int find_acpi_cpu_topology(unsigned int cpu, int level);
> int find_acpi_cpu_topology_package(unsigned int cpu);
> +int find_acpi_cpu_topology_hetero_id(unsigned int cpu);
> int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
> #else
> static inline int find_acpi_cpu_topology(unsigned int cpu, int level)
> @@ -1319,6 +1320,10 @@ static inline int find_acpi_cpu_topology_package(unsigned int cpu)
> {
> return -EINVAL;
> }
static inline int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
> +static int find_acpi_cpu_topology_hetero_id(unsigned int cpu)
> +{
> + return -EINVAL;
> +}
> static inline int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
> {
> return -EINVAL;
