kernel/drivers/acpi/pptt.c, branch linux-6.9.y

ACPI: PPTT: Fix to avoid sleep in the atomic context when PPTT is absent

2023-03-14T19:34:38Z

Commit 0c80f9e165f8 ("ACPI: PPTT: Leave the table mapped for the runtime usage") enabled to map PPTT once on the first invocation of acpi_get_pptt() and never unmapped the same allowing it to be used at runtime with out the hassle of mapping and unmapping the table. This was needed to fetch LLC information from the PPTT in the cpuhotplug path which is executed in the atomic context as the acpi_get_table() might sleep waiting for a mutex. However it missed to handle the case when there is no PPTT on the system which results in acpi_get_pptt() being called from all the secondary CPUs attempting to fetch the LLC information in the atomic context without knowing the absence of PPTT resulting in the splat like below: | BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:164 | in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1 | preempt_count: 1, expected: 0 | RCU nest depth: 0, expected: 0 | no locks held by swapper/1/0. | irq event stamp: 0 | hardirqs last enabled at (0): 0x0 | hardirqs last disabled at (0): copy_process+0x61c/0x1b40 | softirqs last enabled at (0): copy_process+0x61c/0x1b40 | softirqs last disabled at (0): 0x0 | CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.3.0-rc1 #1 | Call trace: | dump_backtrace+0xac/0x138 | show_stack+0x30/0x48 | dump_stack_lvl+0x60/0xb0 | dump_stack+0x18/0x28 | __might_resched+0x160/0x270 | __might_sleep+0x58/0xb0 | down_timeout+0x34/0x98 | acpi_os_wait_semaphore+0x7c/0xc0 | acpi_ut_acquire_mutex+0x58/0x108 | acpi_get_table+0x40/0xe8 | acpi_get_pptt+0x48/0xa0 | acpi_get_cache_info+0x38/0x140 | init_cache_level+0xf4/0x118 | detect_cache_attributes+0x2e4/0x640 | update_siblings_masks+0x3c/0x330 | store_cpu_topology+0x88/0xf0 | secondary_start_kernel+0xd0/0x168 | __secondary_switched+0xb8/0xc0 Update acpi_get_pptt() to consider the fact that PPTT is once checked and is not available on the system and return NULL avoiding any attempts to fetch PPTT and thereby avoiding any possible sleep waiting for a mutex in the atomic context. Fixes: 0c80f9e165f8 ("ACPI: PPTT: Leave the table mapped for the runtime usage") Reported-by: Aishwarya TCV Signed-off-by: Sudeep Holla Tested-by: Pierre Gondois Cc: 6.0+ # 6.0+ Signed-off-by: Rafael J. Wysocki

ACPI: PPTT: Update acpi_find_last_cache_level() to acpi_get_cache_info()

2023-01-18T09:58:40Z

acpi_find_last_cache_level() allows to find the last level of cache for a given CPU. The function is only called on arm64 ACPI based platforms to check for cache information that would be missing in the CLIDR_EL1 register. To allow populating (struct cpu_cacheinfo).num_leaves by only parsing a PPTT, update acpi_find_last_cache_level() to get the 'split_levels', i.e. the number of cache levels being split in data/instruction caches. It is assumed that there will not be data/instruction caches above a unified cache. If a split level consist of one data cache and no instruction cache (or opposite), then the missing cache will still be populated by default with minimal cache information, and maximal cpumask (all non-existing caches have the same fw_token). Suggested-by: Jeremy Linton Signed-off-by: Pierre Gondois Reviewed-by: Jeremy Linton Acked-by: Rafael J. Wysocki Acked-by: Palmer Dabbelt Link: https://lore.kernel.org/r/20230104183033.755668-6-pierre.gondois@arm.com Signed-off-by: Sudeep Holla

ACPI: PPTT: Remove acpi_find_cache_levels()

2023-01-18T09:58:40Z

acpi_find_cache_levels() is used at a single place and is short enough to be merged into the calling function. The removal allows an easier renaming of the calling function in the next patch. Also reorder the local variables in the 'reversed Christmas tree' order. Signed-off-by: Pierre Gondois Reviewed-by: Jeremy Linton Acked-by: Rafael J. Wysocki Acked-by: Palmer Dabbelt Link: https://lore.kernel.org/r/20230104183033.755668-5-pierre.gondois@arm.com Signed-off-by: Sudeep Holla

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

2022-07-22T08:04:43Z

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()

2022-07-04T15:23:23Z

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

2022-07-04T15:22:27Z

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

2021-10-15T09:25:15Z

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

2021-06-07T13:55:02Z

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

2020-01-07T10:46:36Z

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

2019-08-12T11:59:15Z

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