linux-stable.git/arch/x86/kernel/cpu/resctrl/rdtgroup.c, branch linux-rolling-stable

Merge tag 'x86_cache_for_v6.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2025-05-27T16:53:02+00:00

Pull x86 resource control updates from Borislav Petkov:
 "Carve out the resctrl filesystem-related code into fs/resctrl/ so that
  multiple architectures can share the fs API for manipulating their
  respective hw resource control implementation.

  This is the second step in the work towards sharing the resctrl
  filesystem interface, the next one being plugging ARM's MPAM into the
  aforementioned fs API"

* tag 'x86_cache_for_v6.16_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (25 commits)
  MAINTAINERS: Add reviewers for fs/resctrl
  x86,fs/resctrl: Move the resctrl filesystem code to live in /fs/resctrl
  x86/resctrl: Always initialise rid field in rdt_resources_all[]
  x86/resctrl: Relax some asm #includes
  x86/resctrl: Prefer alloc(sizeof(*foo)) idiom in rdt_init_fs_context()
  x86/resctrl: Squelch whitespace anomalies in resctrl core code
  x86/resctrl: Move pseudo lock prototypes to include/linux/resctrl.h
  x86/resctrl: Fix types in resctrl_arch_mon_ctx_{alloc,free}() stubs
  x86/resctrl: Move enum resctrl_event_id to resctrl.h
  x86/resctrl: Move the filesystem bits to headers visible to fs/resctrl
  fs/resctrl: Add boiler plate for external resctrl code
  x86/resctrl: Add 'resctrl' to the title of the resctrl documentation
  x86/resctrl: Split trace.h
  x86/resctrl: Expand the width of domid by replacing mon_data_bits
  x86/resctrl: Add end-marker to the resctrl_event_id enum
  x86/resctrl: Move is_mba_sc() out of core.c
  x86/resctrl: Drop __init/__exit on assorted symbols
  x86/resctrl: Resctrl_exit() teardown resctrl but leave the mount point
  x86/resctrl: Check all domains are offline in resctrl_exit()
  x86/resctrl: Rename resctrl_sched_in() to begin with "resctrl_arch_"
  ...

x86,fs/resctrl: Move the resctrl filesystem code to live in /fs/resctrl

2025-05-16T12:36:09+00:00

Resctrl is a filesystem interface to hardware that provides cache
allocation policy and bandwidth control for groups of tasks or CPUs.

To support more than one architecture, resctrl needs to live in /fs/.

Move the code that is concerned with the filesystem interface to
/fs/resctrl.

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Tested-by: Fenghua Yu 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-25-james.morse@arm.com

x86/resctrl: Prefer alloc(sizeof(*foo)) idiom in rdt_init_fs_context()

2025-05-16T12:33:56+00:00

rdt_init_fs_context() sizes a typed allocation using an explicit
sizeof(type) expression, which checkpatch.pl complains about.

Since this code is about to be factored out and made generic, this
is a good opportunity to fix the code to size the allocation based
on the target pointer instead, to reduce the chance of future mis-
maintenance.

Fix it.

No functional change.

Signed-off-by: Dave Martin 
Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Tested-by: Fenghua Yu 
Tested-by: Peter Newman 
Tested-by: Shaopeng Tan 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-22-james.morse@arm.com

x86/resctrl: Squelch whitespace anomalies in resctrl core code

2025-05-16T12:09:18+00:00

checkpatch.pl complains about some whitespace anomalies in the
resctrl core code.

This doesn't matter, but since this code is about to be factored
out and made generic, this is a good opportunity to fix these
issues and so reduce future checkpatch fuzz.

Fix them.

No functional change.

Signed-off-by: Dave Martin 
Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Tested-by: Fenghua Yu 
Tested-by: Peter Newman 
Tested-by: Shaopeng Tan 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-21-james.morse@arm.com

x86/resctrl: Move the filesystem bits to headers visible to fs/resctrl

2025-05-16T09:35:23+00:00

Once the filesystem parts of resctrl move to fs/resctrl, it cannot rely
on definitions in x86's internal.h.

Move definitions in internal.h that need to be shared between the
filesystem and architecture code to header files that fs/resctrl can
include.

Doing this separately means the filesystem code only moves between files
of the same name, instead of having these changes mixed in too.

Co-developed-by: Dave Martin 
Signed-off-by: Dave Martin 
Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Shaopeng Tan 
Reviewed-by: Tony Luck 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Tested-by: Fenghua Yu 
Tested-by: Carl Worth  # arm64
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-17-james.morse@arm.com

fs/resctrl: Add boiler plate for external resctrl code

2025-05-16T09:05:40+00:00

Add Makefile and Kconfig for fs/resctrl. Add ARCH_HAS_CPU_RESCTRL
for the common parts of the resctrl interface and make X86_CPU_RESCTRL
select this.

Adding an include of asm/resctrl.h to linux/resctrl.h allows the
/fs/resctrl files to switch over to using this header instead.

Co-developed-by: Dave Martin 
Signed-off-by: Dave Martin 
Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Shaopeng Tan 
Reviewed-by: Tony Luck 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Tested-by: Fenghua Yu 
Tested-by: Carl Worth  # arm64
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-16-james.morse@arm.com

x86/resctrl: Expand the width of domid by replacing mon_data_bits

2025-05-16T08:46:45+00:00

MPAM platforms retrieve the cache-id property from the ACPI PPTT table.
The cache-id field is 32 bits wide. Under resctrl, the cache-id becomes
the domain-id, and is packed into the mon_data_bits union bitfield.
The width of cache-id in this field is 14 bits.

Expanding the union would break 32bit x86 platforms as this union is
stored as the kernfs kn->priv pointer. This saved allocating memory
for the priv data storage.

The firmware on MPAM platforms have used the PPTT cache-id field to
expose the interconnect's id for the cache, which is sparse and uses
more than 14 bits. Use of this id is to enable PCIe direct cache
injection hints. Using this feature with VFIO means the value provided
by the ACPI table should be exposed to user-space.

To support cache-id values greater than 14 bits, convert the
mon_data_bits union to a structure. These are shared between control
and monitor groups, and are allocated on first use. The list of
allocated struct mon_data is free'd when the filesystem is umount()ed.

Co-developed-by: Tony Luck 
Signed-off-by: Tony Luck 
Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Tested-by: Fenghua Yu 
Tested-by: Babu Moger 
Tested-by: Shaopeng Tan 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-13-james.morse@arm.com

x86/resctrl: Move is_mba_sc() out of core.c

2025-05-16T08:06:45+00:00

is_mba_sc() is defined in core.c, but has no callers there. It does not access
any architecture private structures.

Move this to rdtgroup.c where the majority of callers are. This makes the move
of the filesystem code to /fs/ cleaner.

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Shaopeng Tan 
Reviewed-by: Tony Luck 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Tested-by: Fenghua Yu 
Tested-by: Carl Worth  # arm64
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-11-james.morse@arm.com

x86/resctrl: Drop init/exit on assorted symbols

2025-05-15T19:06:02+00:00

Because ARM's MPAM controls are probed using MMIO, resctrl can't be
initialised until enough CPUs are online to have determined the system-wide
supported num_closid. Arm64 also supports 'late onlined secondaries', where
only a subset of CPUs are online during boot.

These two combine to mean the MPAM driver may not be able to initialise
resctrl until user-space has brought 'enough' CPUs online.

To allow MPAM to initialise resctrl after __init text has been free'd, remove
all the __init markings from resctrl.

The existing __exit markings cause these functions to be removed by the linker
as it has never been possible to build resctrl as a module. MPAM has an error
interrupt which causes the driver to reset and disable itself. Remove the
__exit markings to allow the MPAM driver to tear down resctrl when an error
occurs.

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Shaopeng Tan 
Reviewed-by: Tony Luck 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Tested-by: Fenghua Yu 
Tested-by: Carl Worth  # arm64
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-10-james.morse@arm.com

x86/resctrl: Resctrl_exit() teardown resctrl but leave the mount point

2025-05-15T19:04:49+00:00

resctrl_exit() was intended for use when the 'resctrl' module was unloaded.
resctrl can't be built as a module, and the kernfs helpers are not exported so
this is unlikely to change. MPAM has an error interrupt which indicates the
MPAM driver has gone haywire. Should this occur tasks could run with the wrong
control values, leading to bad performance for important tasks.  In this
scenario the MPAM driver will reset the hardware, but it needs a way to tell
resctrl that no further configuration should be attempted.

In particular, moving tasks between control or monitor groups does not
interact with the architecture code, so there is no opportunity for the arch
code to indicate that the hardware is no-longer functioning.

Using resctrl_exit() for this leaves the system in a funny state as resctrl is
still mounted, but cannot be un-mounted because the sysfs directory that is
typically used has been removed. Dave Martin suggests this may cause systemd
trouble in the future as not all filesystems can be unmounted.

Add calls to remove all the files and directories in resctrl, and remove the
sysfs_remove_mount_point() call that leaves the system in a funny state. When
triggered, this causes all the resctrl files to disappear. resctrl can be
unmounted, but not mounted again.

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Shaopeng Tan 
Reviewed-by: Tony Luck 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Tested-by: Fenghua Yu 
Tested-by: Carl Worth  # arm64
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Tested-by: Tony Luck 
Link: https://lore.kernel.org/20250515165855.31452-9-james.morse@arm.com