On Fri, Jun 28, 2019 at 8:15 PM Jeremy Linton <jeremy.linton@xxxxxxx> wrote:
>
> ACPI 6.3 adds a flag to the CPU node to indicate whether
> the given PE is a thread. Add a function to return that
> information for a given linux logical CPU.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> ---
> drivers/acpi/pptt.c | 62 +++++++++++++++++++++++++++++++++++++++++++-
> include/linux/acpi.h | 5 ++++
> 2 files changed, 66 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c
> index b72e6afaa8fb..bb6196422fad 100644
> --- a/drivers/acpi/pptt.c
> +++ b/drivers/acpi/pptt.c
> @@ -517,6 +517,52 @@ static int find_acpi_cpu_topology_tag(unsigned int cpu, int level, int flag)
> return retval;
> }
>
> +/**
> + * check_acpi_cpu_flag() - Determine if CPU node has a flag set
> + * @cpu: Kernel logical CPU number
> + * @rev: The PPTT revision defining the flag
> + * @flag: The flag itself
> + *
> + * Check the node representing a CPU for a given flag.
> + *
> + * Return: -ENOENT if the PPTT doesn't exist, the CPU cannot be found or
> + * the table revision isn't new enough.
> + * 1, any passed flag set
> + * 0, flag unset
> + */
> +static int check_acpi_cpu_flag(unsigned int cpu, int rev, u32 flag)
Why not bool?
> +{
> + struct acpi_table_header *table;
> + acpi_status status;
> + u32 acpi_cpu_id = get_acpi_id_for_cpu(cpu);
> + struct acpi_pptt_processor *cpu_node = NULL;
> + int ret = -ENOENT;
> + static int saved_pptt_rev = -1;
> +
> + /* Cache the PPTT revision to avoid repeat table get/put on failure */
This is a rather questionable optimization.
Does the extra table get/put really matter?
> + if (saved_pptt_rev > -1 && saved_pptt_rev < rev)
> + return -ENOENT;
It should be fine to return 'false' here, shouldn't it?
> +
> + status = acpi_get_table(ACPI_SIG_PPTT, 0, &table);
> + if (ACPI_FAILURE(status)) {
> + saved_pptt_rev = 0;
> + acpi_pptt_warn_missing();
> + return ret;
And here?
> + }
> +
> + saved_pptt_rev = table->revision;
> +
> + if (saved_pptt_rev >= rev)
> + cpu_node = acpi_find_processor_node(table, acpi_cpu_id);
> +
> + if (cpu_node)
> + ret = (cpu_node->flags & flag) != 0;
And this can be
ret = !!(cpu_node->flags & flag);
> +
> + acpi_put_table(table);
> +
> + return ret;
> +}
> +
> /**
> * acpi_find_last_cache_level() - Determines the number of cache levels for a PE
> * @cpu: Kernel logical CPU number
> @@ -581,6 +627,21 @@ int cache_setup_acpi(unsigned int cpu)
> return status;
> }
>
> +/**
> + * acpi_pptt_cpu_is_thread() - Determine if CPU is a thread
> + * @cpu: Kernel logical CPU number
> + *
> + *
> + * Return: 1, a thread
> + * 0, not a thread
> + * -ENOENT ,if the PPTT doesn't exist, the CPU cannot be found or
> + * the table revision isn't new enough.
> + */
> +int acpi_pptt_cpu_is_thread(unsigned int cpu)
> +{
> + return check_acpi_cpu_flag(cpu, 2, ACPI_PPTT_ACPI_PROCESSOR_IS_THREAD);
> +}
> +
> /**
> * find_acpi_cpu_topology() - Determine a unique topology value for a given CPU
> * @cpu: Kernel logical CPU number
> @@ -641,7 +702,6 @@ int find_acpi_cpu_cache_topology(unsigned int cpu, int level)
> return ret;
> }
>
> -
> /**
> * find_acpi_cpu_topology_package() - Determine a unique CPU package value
> * @cpu: Kernel logical CPU number
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index d315d86844e4..3e339375e213 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1301,10 +1301,15 @@ static inline int lpit_read_residency_count_address(u64 *address)
> #endif
>
> #ifdef CONFIG_ACPI_PPTT
> +int acpi_pptt_cpu_is_thread(unsigned int cpu);
> int find_acpi_cpu_topology(unsigned int cpu, int level);
> int find_acpi_cpu_topology_package(unsigned int cpu);
> int find_acpi_cpu_cache_topology(unsigned int cpu, int level);
> #else
> +static inline int acpi_pptt_cpu_is_thread(unsigned int cpu)
> +{
> + return -EINVAL;
> +}
> static inline int find_acpi_cpu_topology(unsigned int cpu, int level)
> {
> return -EINVAL;
> --
> 2.21.0
>
