在 03/07/2019 17:24, Rafael J. Wysocki 写道:
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?
I would have made saved_pptt_rev a global, but, indeed, caching the
value is not so important.
+ 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);
+}
You could also consider the following to avoid the tri-state return value:
bool acpi_pptt_cpu_find_threaded(unsigned int cpu, bool *is_threaded)
+
/**
* 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
.
