linux-stable.git/drivers/resctrl/mpam_resctrl.c, branch master

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

arm_mpam: resctrl: Add kunit test for control format conversions

2026-03-27T15:31:04+00:00

resctrl specifies the format of the control schemes, and these don't match
the hardware.

Some of the conversions are a bit hairy - add some kunit tests.

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 
Signed-off-by: Dave Martin 
[morse: squashed enough of Dave's fixes in here that it's his patch now!]
Signed-off-by: Ben Horgan 
Signed-off-by: James Morse

arm_mpam: resctrl: Add support for 'MB' resource

2026-03-27T15:30:55+00:00

resctrl supports 'MB', as a percentage throttling of traffic from the
L3. This is the control that mba_sc uses, so ideally the class chosen
should be as close as possible to the counters used for mbm_total. If there
is a single L3, it's the last cache, and the topology of the memory matches
then the traffic at the memory controller will be equivalent to that at
egress of the L3. If these conditions are met allow the memory class to
back MB.

MB's percentage control should be backed either with the fixed point
fraction MBW_MAX or bandwidth portion bitmaps. The bandwidth portion
bitmaps is not used as its tricky to pick which bits to use to avoid
contention, and may be possible to expose this as something other than a
percentage in the future.

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: Wait for cacheinfo to be ready

2026-03-27T15:30:49+00:00

In order to calculate the rmid realloc threshold the size of the cache
needs to be known. Cache domains will also be named after the cache id. So
that this information can be extracted from cacheinfo we need to wait for
it to be ready. The cacheinfo information is populated in device_initcall()
so we wait for that.

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 
Signed-off-by: Ben Horgan 
Signed-off-by: James Morse