linux.git/drivers/acpi/pptt.c, branch v6.0

ACPI: PPTT: Leave the table mapped for the runtime usage

2022-07-22T08:04:43+00:00

Currently, everytime an information needs to be fetched from the PPTT,
the table is mapped via acpi_get_table() and unmapped after the use via
acpi_put_table() which is fine. However we do this at runtime especially
when the CPU is hotplugged out and plugged in back since we re-populate
the cache topology and other information.

However, with the support to fetch LLC information from the PPTT in the
cpuhotplug path which is executed in the atomic context, it is preferred
to avoid mapping and unmapping of the PPTT for every single use as the
acpi_get_table() might sleep waiting for a mutex.

In order to avoid the same, the table is needs to just mapped once on
the boot CPU and is never unmapped allowing it to be used at runtime
with out the hassle of mapping and unmapping the table.

Reported-by: Guenter Roeck 
Cc: Rafael J. Wysocki 
Signed-off-by: Sudeep Holla 

--

Hi Rafael,

Sorry to bother you again on this PPTT changes. Guenter reported an issue
with lockdep enabled in -next that include my cacheinfo/arch_topology changes
to utilise LLC from PPTT in the CPU hotplug path.

Please ack the change once you are happy so that I can get it merged with
other fixes via Greg's tree.

Regards,
Sudeep

Acked-by: Rafael J. Wysocki 
Link: https://lore.kernel.org/r/20220720-arch_topo_fixes-v3-2-43d696288e84@arm.com
Signed-off-by: Greg Kroah-Hartman

ACPI: Remove the unused find_acpi_cpu_cache_topology()

2022-07-04T15:23:23+00:00

The sole user of this find_acpi_cpu_cache_topology() was arm64 topology
which is now consolidated into the generic arch_topology without the need
of this function.

Drop the unused function find_acpi_cpu_cache_topology().

Link: https://lore.kernel.org/r/20220704101605.1318280-22-sudeep.holla@arm.com
Cc: Rafael J. Wysocki 
Reported-by: Ionela Voinescu 
Tested-by: Conor Dooley 
Acked-by: Rafael J. Wysocki 
Signed-off-by: Sudeep Holla

ACPI: PPTT: Use table offset as fw_token instead of virtual address

2022-07-04T15:22:27+00:00

There is need to use the cache sharing information quite early during
the boot before the secondary cores are up and running. The permanent
memory map for all the ACPI tables(via acpi_permanent_mmap) is turned
on in acpi_early_init() which is quite late for the above requirement.

As a result there is possibility that the ACPI PPTT gets mapped to
different virtual addresses. In such scenarios, using virtual address as
fw_token before the acpi_permanent_mmap is enabled results in different
fw_token for the same cache entity and hence wrong cache sharing
information will be deduced based on the same.

Instead of using virtual address, just use the table offset as the
unique firmware token for the caches. The same offset is used as
ACPI identifiers if the firmware has not set a valid one for other
entries in the ACPI PPTT.

Link: https://lore.kernel.org/r/20220704101605.1318280-2-sudeep.holla@arm.com
Cc: linux-acpi@vger.kernel.org
Tested-by: Ionela Voinescu 
Tested-by: Conor Dooley 
Acked-by: Rafael J. Wysocki 
Signed-off-by: Sudeep Holla

topology: Represent clusters of CPUs within a die

2021-10-15T09:25:15+00:00

Both ACPI and DT provide the ability to describe additional layers of
topology between that of individual cores and higher level constructs
such as the level at which the last level cache is shared.
In ACPI this can be represented in PPTT as a Processor Hierarchy
Node Structure [1] that is the parent of the CPU cores and in turn
has a parent Processor Hierarchy Nodes Structure representing
a higher level of topology.

For example Kunpeng 920 has 6 or 8 clusters in each NUMA node, and each
cluster has 4 cpus. All clusters share L3 cache data, but each cluster
has local L3 tag. On the other hand, each clusters will share some
internal system bus.

+-----------------------------------+                          +---------+
|  +------+    +------+             +--------------------------+         |
|  | CPU0 |    | cpu1 |             |    +-----------+         |         |
|  +------+    +------+             |    |           |         |         |
|                                   +----+    L3     |         |         |
|  +------+    +------+   cluster   |    |    tag    |         |         |
|  | CPU2 |    | CPU3 |             |    |           |         |         |
|  +------+    +------+             |    +-----------+         |         |
|                                   |                          |         |
+-----------------------------------+                          |         |
+-----------------------------------+                          |         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |    +-----------+         |         |
|  +------+    +------+             |    |           |         |         |
|                                   |    |    L3     |         |         |
|  +------+    +------+             +----+    tag    |         |         |
|  |      |    |      |             |    |           |         |         |
|  +------+    +------+             |    +-----------+         |         |
|                                   |                          |         |
+-----------------------------------+                          |   L3    |
                                                               |   data  |
+-----------------------------------+                          |         |
|  +------+    +------+             |    +-----------+         |         |
|  |      |    |      |             |    |           |         |         |
|  +------+    +------+             +----+    L3     |         |         |
|                                   |    |    tag    |         |         |
|  +------+    +------+             |    |           |         |         |
|  |      |    |      |             |    +-----------+         |         |
|  +------+    +------+             +--------------------------+         |
+-----------------------------------|                          |         |
+-----------------------------------|                          |         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |    +-----------+         |         |
|  +------+    +------+             |    |           |         |         |
|                                   +----+    L3     |         |         |
|  +------+    +------+             |    |    tag    |         |         |
|  |      |    |      |             |    |           |         |         |
|  +------+    +------+             |    +-----------+         |         |
|                                   |                          |         |
+-----------------------------------+                          |         |
+-----------------------------------+                          |         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |   +-----------+          |         |
|  +------+    +------+             |   |           |          |         |
|                                   |   |    L3     |          |         |
|  +------+    +------+             +---+    tag    |          |         |
|  |      |    |      |             |   |           |          |         |
|  +------+    +------+             |   +-----------+          |         |
|                                   |                          |         |
+-----------------------------------+                          |         |
+-----------------------------------+                          |         |
|  +------+    +------+             +--------------------------+         |
|  |      |    |      |             |  +-----------+           |         |
|  +------+    +------+             |  |           |           |         |
|                                   |  |    L3     |           |         |
|  +------+    +------+             +--+    tag    |           |         |
|  |      |    |      |             |  |           |           |         |
|  +------+    +------+             |  +-----------+           |         |
|                                   |                          +---------+
+-----------------------------------+

That means spreading tasks among clusters will bring more bandwidth
while packing tasks within one cluster will lead to smaller cache
synchronization latency. So both kernel and userspace will have
a chance to leverage this topology to deploy tasks accordingly to
achieve either smaller cache latency within one cluster or an even
distribution of load among clusters for higher throughput.

This patch exposes cluster topology to both kernel and userspace.
Libraried like hwloc will know cluster by cluster_cpus and related
sysfs attributes. PoC of HWLOC support at [2].

Note this patch only handle the ACPI case.

Special consideration is needed for SMT processors, where it is
necessary to move 2 levels up the hierarchy from the leaf nodes
(thus skipping the processor core level).

Note that arm64 / ACPI does not provide any means of identifying
a die level in the topology but that may be unrelate to the cluster
level.

[1] ACPI Specification 6.3 - section 5.2.29.1 processor hierarchy node
    structure (Type 0)
[2] https://github.com/hisilicon/hwloc/tree/linux-cluster

Signed-off-by: Jonathan Cameron 
Signed-off-by: Tian Tao 
Signed-off-by: Barry Song 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210924085104.44806-2-21cnbao@gmail.com

ACPI: tables: PPTT: Populate cache-id if provided by firmware

2021-06-07T13:55:02+00:00

ACPI 6.4 adds a 'cache id' to the PPTT Cache Type Structure.

Copy this property across into the cacheinfo leaf when it was
provided by firmware.

This value gets exposed to userspace as:
/sys/devices/system/cpu/cpu*/cache/index*/id.

See the "Cache IDs" section of Documentation/x86/resctrl.rst.

Co-authored-by: Joey Gouly 
Signed-off-by: James Morse 
Signed-off-by: Joey Gouly 
[ rjw: Subject and changelog edits ]
Signed-off-by: Rafael J. Wysocki

ACPI: PPTT: Consistently use unsigned int as parameter type

2020-01-07T10:46:36+00:00

The fourth parameter 'level' of function 'acpi_find_cache_level()' is
a signed interger, but its caller 'acpi_find_cache_node()' passes that
parameter an unsigned interger.

Make the paramter type inconsistency go away.

Signed-off-by: Tian Tao 
Signed-off-by: Xiongfeng Wang 
[ rjw: Subject/changelog ]
Signed-off-by: Rafael J. Wysocki

ACPI/PPTT: Add support for ACPI 6.3 thread flag

2019-08-12T11:59:15+00:00

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 
Reviewed-by: Sudeep Holla 
Reviewed-by: Robert Richter 
Acked-by: Rafael J. Wysocki 
Signed-off-by: Will Deacon

ACPI/PPTT: Add function to return ACPI 6.3 Identical tokens

2019-06-27T15:53:18+00:00

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.

Acked-by: Rafael J. Wysocki 
Tested-by: Hanjun Guo 
Reviewed-by: Sudeep Holla 
Signed-off-by: Jeremy Linton 
Signed-off-by: Will Deacon

ACPI/PPTT: Modify node flag detection to find last IDENTICAL

2019-06-27T15:52:13+00:00

The ACPI specification implies that the IDENTICAL flag should be
set on all non leaf nodes where the children are identical.
This means that we need to be searching for the last node with
the identical flag set rather than the first one.

Since this flag is also dependent on the table revision, we
need to add a bit of extra code to verify the table revision,
and the next node's state in the traversal. Since we want to
avoid function pointers here, lets just special case
the IDENTICAL flag.

Acked-by: Rafael J. Wysocki 
Tested-by: Hanjun Guo 
Reviewed-by: Sudeep Holla 
Signed-off-by: Jeremy Linton 
Signed-off-by: Will Deacon

ACPI: Fix comment typos

2019-03-26T21:33:43+00:00

Fix some misspellings in comments.  No functional change intended.

Signed-off-by: Bjorn Helgaas 
Signed-off-by: Rafael J. Wysocki