[PATCH 4.18 091/350] ACPI/PPTT: Handle architecturally unknown cache types

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>

[ Upstream commit 59bbff3775c0951300f7b41345a54b999438f8d0 ]

The type of a cache might not be specified by architectural mechanisms (ie
system registers), but its type might be specified in the PPTT.  In this
case, we should populate the type of the cache, rather than leave it
undefined.

This fixes the issue where the cacheinfo driver will not populate sysfs
for such caches, resulting in the information missing from utilities like
lstopo and lscpu, thus degrading the user experience.

Fixes: 2bd00bcd73e5 (ACPI/PPTT: Add Processor Properties Topology Table parsing)
Reported-by: Vijaya Kumar K <vkilari@xxxxxxxxxxxxxx>
Signed-off-by: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/acpi/pptt.c |   33 +++++++++++++--------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

--- a/drivers/acpi/pptt.c
+++ b/drivers/acpi/pptt.c
@@ -338,9 +338,6 @@ static struct acpi_pptt_cache *acpi_find
 	return found;
 }
 
-/* total number of attributes checked by the properties code */
-#define PPTT_CHECKED_ATTRIBUTES 4
-
 /**
  * update_cache_properties() - Update cacheinfo for the given processor
  * @this_leaf: Kernel cache info structure being updated
@@ -357,25 +354,15 @@ static void update_cache_properties(stru
 				    struct acpi_pptt_cache *found_cache,
 				    struct acpi_pptt_processor *cpu_node)
 {
-	int valid_flags = 0;
-
 	this_leaf->fw_token = cpu_node;
-	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID) {
+	if (found_cache->flags & ACPI_PPTT_SIZE_PROPERTY_VALID)
 		this_leaf->size = found_cache->size;
-		valid_flags++;
-	}
-	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID) {
+	if (found_cache->flags & ACPI_PPTT_LINE_SIZE_VALID)
 		this_leaf->coherency_line_size = found_cache->line_size;
-		valid_flags++;
-	}
-	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID) {
+	if (found_cache->flags & ACPI_PPTT_NUMBER_OF_SETS_VALID)
 		this_leaf->number_of_sets = found_cache->number_of_sets;
-		valid_flags++;
-	}
-	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID) {
+	if (found_cache->flags & ACPI_PPTT_ASSOCIATIVITY_VALID)
 		this_leaf->ways_of_associativity = found_cache->associativity;
-		valid_flags++;
-	}
 	if (found_cache->flags & ACPI_PPTT_WRITE_POLICY_VALID) {
 		switch (found_cache->attributes & ACPI_PPTT_MASK_WRITE_POLICY) {
 		case ACPI_PPTT_CACHE_POLICY_WT:
@@ -402,11 +389,17 @@ static void update_cache_properties(stru
 		}
 	}
 	/*
-	 * If the above flags are valid, and the cache type is NOCACHE
-	 * update the cache type as well.
+	 * If cache type is NOCACHE, then the cache hasn't been specified
+	 * via other mechanisms.  Update the type if a cache type has been
+	 * provided.
+	 *
+	 * Note, we assume such caches are unified based on conventional system
+	 * design and known examples.  Significant work is required elsewhere to
+	 * fully support data/instruction only type caches which are only
+	 * specified in PPTT.
 	 */
 	if (this_leaf->type == CACHE_TYPE_NOCACHE &&
-	    valid_flags == PPTT_CHECKED_ATTRIBUTES)
+	    found_cache->flags & ACPI_PPTT_CACHE_TYPE_VALID)
 		this_leaf->type = CACHE_TYPE_UNIFIED;
 }