PPTT handle Handle architecturally unknown cache types
Subsystems (2)
v4 cover PPTT handle Handle architecturally unknown cache types
The ARM Architecture Reference Manual allows for caches to be "invisible" and thus not specified in the system registers under some scenarios such as if the cache cannot be managed by set/way operations.
However, such caches may be specified in the ACPI PPTT table for workload performance/scheduling optimizations.
Currently such caches can cause an error in lscpu -
lscpu: cannot open /sys/devices/system/cpu/cpu0/cache/index3/type: No such file or directory
and result in no output, providing a poor user experience. lstopo is also affected as such caches are not included in the output.
Address these issues by attempting to be a little more discerning about when cache information is provided to userspace, and also utilize all sources for cache information when possible.
[v4]
-Collected all current tags and ammended to individual patches -Removed PPTT_CHECKED_ATTRIBUTES
[v3]
-removed valid flag in PPTT
-Added Jeremy Linton's reviewed-by
[v2]
-Updated cacheinfo per Sudeep's suggestion
-Integrated the PPTT fix into existing PPTT code per Sudeep's suggestion
Jeffrey Hugo (2):
drivers: base: cacheinfo: Do not populate sysfs for unknown cache
types
ACPI/PPTT: Handle architecturally unknown cache types
drivers/acpi/pptt.c | 15 +++++++++++---- drivers/base/cacheinfo.c | 2 ++ 2 files changed, 13 insertions(+), 4 deletions(-)
Signature · 3 lines
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
PATCH v4 1/2 drivers: base: cacheinfo: Do not populate sysfs for unknown cache types
If a cache has an unknown type because neither the hardware nor the firmware told us, an entry in the sysfs tree will be made, but the type file will not be present. lscpu depends on the type file being present for every entry, and will error out without printing system information if lscpu cannot open the type file.
Presenting information about a cache without indicating its type is not useful, therefore if we hit a cache with an unknown type, stop populating sysfs so that userspace has the maximum amount of useful information.
This addresses the following lscpu error, which prevents any output.
lscpu: cannot open /sys/devices/system/cpu/cpu0/cache/index3/type: No such file or directory
--- drivers/base/cacheinfo.c | 2 ++ 1 file changed, 2 insertions(+)
drivers/base/cacheinfo.c +2 -0
@@ -615,6 +615,8 @@ static int cache_add_dev(unsigned int cpu) this_leaf = this_cpu_ci->info_list + i;if (this_leaf->disable_sysfs)continue ; +if (this_leaf->type ==CACHE_TYPE_NOCACHE ) +break ; cache_groups =cache_get_attribute_groups (this_leaf); ci_dev =cpu_device_create (parent, this_leaf, cache_groups,"index%1u" , i);
Signature · 3 lines
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
Re: [PATCH v4 1/2] drivers: base: cacheinfo: Do not populate sysfs for unknown cache types
Quoted 14 lines · Jeffrey Hugo
If a cache has an unknown type because neither the hardware nor the firmware told us, an entry in the sysfs tree will be made, but the type file will not be present. lscpu depends on the type file being present for every entry, and will error out without printing system information if lscpu cannot open the type file.
Presenting information about a cache without indicating its type is not useful, therefore if we hit a cache with an unknown type, stop populating sysfs so that userspace has the maximum amount of useful information.
This addresses the following lscpu error, which prevents any output.
lscpu: cannot open/sys/devices/system/cpu/cpu0/cache/index3/type: No such file or directory
Quoted 7 lines
Suggested-by Sudeep Holla <[email protected]>Signed-off-by Jeffrey Hugo <[email protected]>Reviewed-by Jeremy Linton <[email protected]>Reviewed-by Sudeep Holla <[email protected]>--- drivers/base/cacheinfo.c | 2 ++ 1 file changed, 2 insertions(+)
PATCH v4 2/2 ACPI/PPTT: Handle architecturally unknown cache types
In reply to Jeffrey HugoThe 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.
--- drivers/acpi/pptt.c | 33 +++++++++++++-------------------- 1 file changed, 13 insertions(+), 20 deletions(-)
drivers/acpi/pptt.c +13 -20
@@ -338,9 +338,6 @@ static struct acpi_pptt_cache *acpi_find_cache_node(struct acpi_table_header *tareturn 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(struct cacheinfo *this_leaf,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(struct cacheinfo *this_leaf, } }/* -* 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 ; }
Signature · 3 lines
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
Quoted 31 lines · CEST Jeffrey Hugo
The ARM Architecture Reference Manual allows for caches to be "invisible" and thus not specified in the system registers under some scenarios such as if the cache cannot be managed by set/way operations.
However, such caches may be specified in the ACPI PPTT table for workload performance/scheduling optimizations.
Currently such caches can cause an error in lscpu -
lscpu: cannot open
/sys/devices/system/cpu/cpu0/cache/index3/type: No such file or directoryand result in no output, providing a poor user experience. lstopo is also affected as such caches are not included in the output.
Address these issues by attempting to be a little more discerning about when cache information is provided to userspace, and also utilize all sources for cache information when possible.
[v4]
(quoted diff) +0
-2-Collected all current tags and ammended to individual patches -Removed PPTT_CHECKED_ATTRIBUTES[v3]
(quoted diff) +0
-2-removed valid flag in PPTT -Added Jeremy Linton's reviewed-by[v2]
(quoted diff) +0
-2-Updated cacheinfo per Sudeep's suggestion -Integrated the PPTT fix into existing PPTT code per Sudeep's suggestion
Quoted 10 lines
Jeffrey Hugo (2):
drivers: base: cacheinfo: Do not populate sysfs for unknown cache
types
ACPI/PPTT: Handle architecturally unknown cache typesdrivers/acpi/pptt.c | 15 +++++++++++---- drivers/base/cacheinfo.c | 2 ++ 2 files changed, 13 insertions(+), 4 deletions(-)
Both patches applied, thanks!