kernel/linux.git/drivers/resctrl/mpam_resctrl.c, branch v7.3-rc1

arm_mpam: resctrl: Add resctrl_arch_cntr_read() & resctrl_arch_reset_cntr()

2026-08-02T09:33:43+00:00

When used in 'mbm_event' mode, ABMC emulation, resctrl uses arch hooks to read and reset the memory bandwidth utilization (MBWU) counters. Add these. Signed-off-by: James Morse Signed-off-by: Ben Horgan Tested-by: Shaopeng Tan Tested-by: Fenghua Yu Tested-by: Gavin Shan Reviewed-by: Jonathan Cameron Reviewed-by: Shaopeng Tan Reviewed-by: Fenghua Yu Reviewed-by: Gavin Shan Signed-off-by: Will Deacon

arm_mpam: resctrl: Add resctrl_arch_config_cntr() for ABMC use

2026-08-02T09:33:43+00:00

ABMC, mbm_event mode, has a helper resctrl_arch_config_cntr() for changing the mapping between 'cntr_id' and a CLOSID/RMID pair. Add the helper. For MPAM this is done by updating the mon->mbwu_idx_to_mon[] array, and as usual CDP means it needs doing in three different ways. Signed-off-by: James Morse Signed-off-by: Ben Horgan Tested-by: Shaopeng Tan Tested-by: Fenghua Yu Tested-by: Gavin Shan Reviewed-by: Jonathan Cameron Reviewed-by: Shaopeng Tan Reviewed-by: Fenghua Yu Reviewed-by: Gavin Shan Signed-off-by: Will Deacon

arm_mpam: resctrl: Pre-allocate assignable monitors

2026-08-02T09:33:43+00:00

MPAM is able to emulate ABMC, i.e. mbm_event mode, by making memory bandwidth monitors assignable. Rather than supporting the 'default' mbm_assign_mode always use 'mbm_event' mode even if there are sufficient memory bandwidth monitors. The per monitor event configuration is only provided by resctrl when in 'mbm_event' mode and so only allowing 'mbm_event' mode will make it easier to support per-monitor event configuration for MPAM. For the moment, the only event supported is mbm_total_event with no bandwidth type configuration. The 'mbm_assign_mode' file will still show 'default' when there is no support for memory bandwidth monitoring. The monitors need to be allocated from the driver, and mapped to whichever control/monitor group resctrl wants to use them with. Add a second array to hold the monitor values indexed by resctrl's cntr_id. When CDP is in use, two monitors are needed so the available number of counters halves. Platforms with one monitor will have zero monitors when CDP is in use. Co-developed-by: James Morse Signed-off-by: James Morse Signed-off-by: Ben Horgan Tested-by: Shaopeng Tan Tested-by: Fenghua Yu Tested-by: Gavin Shan Reviewed-by: Shaopeng Tan Reviewed-by: Fenghua Yu Reviewed-by: Gavin Shan Signed-off-by: Will Deacon

arm_mpam: resctrl: Pick classes for use as MBM counters

2026-08-02T09:33:43+00:00

resctrl has two types of bandwidth counters, NUMA-local and global. MPAM can only count globally; either using MSC at the L3 cache or in the memory controllers. When global and local equate to the same thing continue just to call it global. Pick the corresponding MPAM classes to back the MBM counters. As resctrl requires all monitors to be at the L3 cache, we can only use the counters at the memory controllers when they have the same topology as the L3 cache and the traffic they see if the same. In particular, for the bandwidth counters at the memory controllers to be exposed to resctrl it is required there is a single L3 cache and a single NUMA node as otherwise cross NUMA traffic will be counted at the wrong instance. Signed-off-by: James Morse Signed-off-by: Ben Horgan Tested-by: Shaopeng Tan Tested-by: Zeng Heng Tested-by: Fenghua Yu Tested-by: Gavin Shan Reviewed-by: Shaopeng Tan Reviewed-by: Jonathan Cameron Reviewed-by: Fenghua Yu Reviewed-by: Gavin Shan Signed-off-by: Will Deacon

arm_mpam: resctrl: Make resctrl_mon_ctx_waiters static

2026-04-17T16:48:07+00:00

resctrl_mon_ctx_waiters is not used outside of this file, so make it static. This fixes the sparse warning: drivers/resctrl/mpam_resctrl.c:25:1: warning: symbol 'resctrl_mon_ctx_waiters' was not declared. Should it be static? Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202603281842.c2K96tJA-lkp@intel.com/ Fixes: 2a3c79c61539 ("arm_mpam: resctrl: Allow resctrl to allocate monitors") Signed-off-by: Ben Horgan Reviewed-by: Gavin Shan Signed-off-by: James Morse

arm_mpam: resctrl: Fix the check for no monitor components found

2026-04-17T16:48:07+00:00

Dan Carpenter reports that, in mpam_resctrl_alloc_domain(), any_mon_comp is used in an 'if' condition when it may be uninitialized. Initialize it to NULL so that the check behaves correctly when no monitor components are found. Reported-by: Dan Carpenter Fixes: 264c285999fc ("arm_mpam: resctrl: Add monitor initialisation and domain boilerplate") Signed-off-by: Ben Horgan Reviewed-by: Gavin Shan Signed-off-by: James Morse

arm_mpam: resctrl: Fix MBA CDP alloc_capable handling on unmount

2026-04-17T16:43:57+00:00

The code to set MBA's alloc_capable to true appears to be trying to restore alloc_capable on unmount. This can never work because resctrl_arch_set_cdp_enabled() is never invoked with RDT_RESOURCE_MBA as the rid parameter. Consequently, mpam_resctrl_controls[RDT_RESOURCE_MBA].cdp_enabled always remains false. The alloc_capable setting in resctrl_arch_set_cdp_enabled() is to re-enable MBA if the caller opts in to separate control values using CDP for this resource. This doesn't happen today. Add a comment to describe this. However a bug remains where MBA allocation is permanently disabled after the mount with CDP option. Remounting without CDP cannot restore the MBA partition capability. Add a check to re-enable MBA when CDP is disabled, which happens on unmount. Fixes: 6789fb99282c ("arm_mpam: resctrl: Add CDP emulation") Signed-off-by: Zeng Heng [ morse: Added comment for existing code, added hunk to fix this bug from Ben H ] Reviewed-by: James Morse Signed-off-by: James Morse

arm_mpam: resctrl: Call resctrl_init() on platforms that can support resctrl

2026-03-27T15:32:19+00:00

Now that MPAM links against resctrl, call resctrl_init() to register the filesystem and setup resctrl's structures. Tested-by: Gavin Shan Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Zeng Heng Tested-by: Punit Agrawal Tested-by: Jesse Chick Reviewed-by: Zeng Heng Reviewed-by: Shaopeng Tan Reviewed-by: Jonathan Cameron Reviewed-by: Gavin Shan Co-developed-by: Ben Horgan Signed-off-by: Ben Horgan Signed-off-by: James Morse

arm_mpam: resctrl: Add empty definitions for assorted resctrl functions

2026-03-27T15:32:04+00:00

A few resctrl features and hooks need to be provided, but aren't needed or supported on MPAM platforms. resctrl has individual hooks to separately enable and disable the closid/partid and rmid/pmg context switching code. For MPAM this is all the same thing, as the value in struct task_struct is used to cache the value that should be written to hardware. arm64's context switching code is enabled once MPAM is usable, but doesn't touch the hardware unless the value has changed. For now event configuration is not supported, and can be turned off by returning 'false' from resctrl_arch_is_evt_configurable(). The new io_alloc feature is not supported either, always return false from the enable helper to indicate and fail the enable. Add this, and empty definitions for the other hooks. Tested-by: Gavin Shan Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Zeng Heng Tested-by: Punit Agrawal Tested-by: Jesse Chick Reviewed-by: Zeng Heng Reviewed-by: Shaopeng Tan Reviewed-by: Jonathan Cameron Reviewed-by: Gavin Shan Co-developed-by: Ben Horgan Signed-off-by: Ben Horgan Signed-off-by: James Morse

arm_mpam: resctrl: Update the rmid reallocation limit

2026-03-27T15:31:57+00:00

resctrl's limbo code needs to be told when the data left in a cache is small enough for the partid+pmg value to be re-allocated. x86 uses the cache size divided by the number of rmid users the cache may have. Do the same, but for the smallest cache, and with the number of partid-and-pmg users. Tested-by: Gavin Shan Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Zeng Heng Tested-by: Punit Agrawal Tested-by: Jesse Chick Reviewed-by: Zeng Heng Reviewed-by: Shaopeng Tan Reviewed-by: Jonathan Cameron Reviewed-by: Gavin Shan Co-developed-by: Ben Horgan Signed-off-by: Ben Horgan Signed-off-by: James Morse