linux.git/drivers/resctrl/mpam_resctrl.c, branch v7.1-rc2

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

arm_mpam: resctrl: Add resctrl_arch_rmid_read()

2026-03-27T15:31:50+00:00

resctrl uses resctrl_arch_rmid_read() to read counters. CDP emulation means
the counter may need reading in three different ways.

The helpers behind the resctrl_arch_ functions will be re-used for the ABMC
equivalent functions.

Add the rounding helper for checking monitor values while we're here.

Tested-by: Gavin Shan 
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Zeng Heng 
Tested-by: Jesse Chick 
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: Allow resctrl to allocate monitors

2026-03-27T15:31:38+00:00

When resctrl wants to read a domain's 'QOS_L3_OCCUP', it needs to allocate
a monitor on the corresponding resource. Monitors are allocated by class
instead of component.

Add helpers to allocate a CSU monitor. These helper return an out of range
value for MBM counters.

Allocating a montitor context is expected to block until hardware resources
become available. This only makes sense for QOS_L3_OCCUP as unallocated MBM
counters are losing data.

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 support for csu counters

2026-03-27T15:31:23+00:00

resctrl exposes a counter via a file named llc_occupancy. This isn't really
a counter as its value goes up and down, this is a snapshot of the cache
storage usage monitor.

Add some picking code which will only find an L3. The resctrl counter
file is called llc_occupancy but we don't check it is the last one as
it is already identified as L3.

Tested-by: Shaopeng Tan 
Tested-by: Zeng Heng 
Tested-by: Punit Agrawal 
Tested-by: Gavin Shan 
Tested-by: Jesse Chick 
Reviewed-by: Zeng Heng 
Reviewed-by: Shaopeng Tan 
Reviewed-by: Jonathan Cameron 
Reviewed-by: Gavin Shan 
Co-developed-by: Dave Martin 
Signed-off-by: Dave Martin 
Co-developed-by: Ben Horgan 
Signed-off-by: Ben Horgan 
Signed-off-by: James Morse

arm_mpam: resctrl: Add monitor initialisation and domain boilerplate

2026-03-27T15:31:10+00:00

Add the boilerplate that tells resctrl about the mpam monitors that are
available. resctrl expects all (non-telemetry) monitors to be on the L3 and
so advertise them there and invent an L3 resctrl resource if required. The
L3 cache itself has to exist as the cache ids are used as the domain
ids.

Bring the resctrl monitor domains online and offline based on the cpus
they contain.

Support for specific monitor types is left to later.

Tested-by: Punit Agrawal 
Reviewed-by: Zeng Heng 
Reviewed-by: Jonathan Cameron 
Signed-off-by: Ben Horgan 
Reviewed-by: Gavin Shan 
Tested-by: Gavin Shan 
Tested-by: Shaopeng Tan 
Tested-by: Jesse Chick 
Signed-off-by: James Morse