linux.git/arch/x86/kernel/cpu/resctrl, branch v6.15

x86/resctrl: Fix rdtgroup_mkdir()'s unlocked use of kernfs_node::name

2025-04-09T09:35:08+00:00

Since

  741c10b096bc ("kernfs: Use RCU to access kernfs_node::name.")

a helper rdt_kn_name() that checks that rdtgroup_mutex is held has been used
for all accesses to the kernfs node name.

rdtgroup_mkdir() uses the name to determine if a valid monitor group is being
created by checking the parent name is "mon_groups". This is done without
holding rdtgroup_mutex, and now triggers the following warning:

  | WARNING: suspicious RCU usage
  | 6.15.0-rc1 #4465 Tainted: G            E
  | -----------------------------
  | arch/x86/kernel/cpu/resctrl/internal.h:408 suspicious rcu_dereference_check() usage!
  [...]
  | Call Trace:
  |  
  |  dump_stack_lvl
  |  lockdep_rcu_suspicious.cold
  |  is_mon_groups
  |  rdtgroup_mkdir
  |  kernfs_iop_mkdir
  |  vfs_mkdir
  |  do_mkdirat
  |  __x64_sys_mkdir
  |  do_syscall_64
  |  entry_SYSCALL_64_after_hwframe

Creating a control or monitor group calls mkdir_rdt_prepare(), which uses
rdtgroup_kn_lock_live() to take the rdtgroup_mutex.

To avoid taking and dropping the lock, move the check for the monitor group
name and position into mkdir_rdt_prepare() so that it occurs under
rdtgroup_mutex. Hoist is_mon_groups() earlier in the file.

  [ bp: Massage. ]

Fixes: 741c10b096bc ("kernfs: Use RCU to access kernfs_node::name.")
Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Acked-by: Ingo Molnar 
Link: https://lore.kernel.org/r/20250407124637.2433230-1-james.morse@arm.com

Merge tag 'driver-core-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core

2025-04-01T18:02:03+00:00

Pull driver core updatesk from Greg KH:
 "Here is the big set of driver core updates for 6.15-rc1. Lots of stuff
  happened this development cycle, including:

   - kernfs scaling changes to make it even faster thanks to rcu

   - bin_attribute constify work in many subsystems

   - faux bus minor tweaks for the rust bindings

   - rust binding updates for driver core, pci, and platform busses,
     making more functionaliy available to rust drivers. These are all
     due to people actually trying to use the bindings that were in
     6.14.

   - make Rafael and Danilo full co-maintainers of the driver core
     codebase

   - other minor fixes and updates"

* tag 'driver-core-6.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core: (52 commits)
  rust: platform: require Send for Driver trait implementers
  rust: pci: require Send for Driver trait implementers
  rust: platform: impl Send + Sync for platform::Device
  rust: pci: impl Send + Sync for pci::Device
  rust: platform: fix unrestricted &mut platform::Device
  rust: pci: fix unrestricted &mut pci::Device
  rust: device: implement device context marker
  rust: pci: use to_result() in enable_device_mem()
  MAINTAINERS: driver core: mark Rafael and Danilo as co-maintainers
  rust/kernel/faux: mark Registration methods inline
  driver core: faux: only create the device if probe() succeeds
  rust/faux: Add missing parent argument to Registration::new()
  rust/faux: Drop #[repr(transparent)] from faux::Registration
  rust: io: fix devres test with new io accessor functions
  rust: io: rename `io::Io` accessors
  kernfs: Move dput() outside of the RCU section.
  efi: rci2: mark bin_attribute as __ro_after_init
  rapidio: constify 'struct bin_attribute'
  firmware: qemu_fw_cfg: constify 'struct bin_attribute'
  powerpc/perf/hv-24x7: Constify 'struct bin_attribute'
  ...

x86/resctrl: Move get_{mon,ctrl}_domain_from_cpu() to live with their callers

2025-03-12T11:24:58+00:00

Each of get_{mon,ctrl}_domain_from_cpu() only has one caller.

Once the filesystem code is moved to /fs/, there is no equivalent to
core.c.

Move these functions to each live next to their caller. This allows
them to be made static and the header file entries to be removed.

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Fenghua Yu 
Reviewed-by: Reinette Chatre 
Reviewed-by: Babu Moger 
Reviewed-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Shaopeng Tan 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Link: https://lore.kernel.org/r/20250311183715.16445-31-james.morse@arm.com

x86/resctrl: Move get_config_index() to a header

2025-03-12T11:24:54+00:00

get_config_index() is used by the architecture specific code to map
a CLOSID+type pair to an index in the configuration arrays.

MPAM needs to do this too to preserve the ABI to user-space, there is no
reason to do it differently.

Move the helper to a header file to allow all architectures that either
use or emulate CDP to use the same pattern of CLOSID values. Moving
this to a header file means it must be marked inline, which matches
the existing compiler choice for this static function.

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 
Reviewed-by: Babu Moger 
Tested-by: Carl Worth  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Babu Moger 
Link: https://lore.kernel.org/r/20250311183715.16445-30-james.morse@arm.com

x86/resctrl: Handle throttle_mode for SMBA resources

2025-03-12T11:24:46+00:00

Now that the visibility of throttle_mode is being managed by resctrl, it
should consider resources other than MBA that may have a throttle_mode.  SMBA
is one such resource.

Extend thread_throttle_mode_init() to check SMBA for a throttle_mode.

Adding support for multiple resources means it is possible for a platform with
both MBA and SMBA, but an undefined throttle_mode on one of them to make the
file visible.

Add the 'undefined' case to rdt_thread_throttle_mode_show().

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Reviewed-by: Babu Moger 
Reviewed-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Shaopeng Tan 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Link: https://lore.kernel.org/r/20250311183715.16445-29-james.morse@arm.com

x86/resctrl: Move RFTYPE flags to be managed by resctrl

2025-03-12T11:24:37+00:00

resctrl_file_fflags_init() is called from the architecture specific code to
make the 'thread_throttle_mode' file visible. The architecture specific code
has already set the membw.throttle_mode in the rdt_resource.

This forces the RFTYPE flags used by resctrl to be exposed to the architecture
specific code.

This doesn't need to be specific to the architecture, the throttle_mode can be
used by resctrl to determine if the 'thread_throttle_mode' file should be
visible. This allows the RFTYPE flags to be private to resctrl.

Add thread_throttle_mode_init(), and use it to call resctrl_file_fflags_init()
from resctrl_init(). This avoids publishing an extra function between the
architecture and filesystem code.

Signed-off-by: James Morse 
Signed-off-by: Borislav Petkov (AMD) 
Reviewed-by: Reinette Chatre 
Reviewed-by: Fenghua Yu 
Reviewed-by: Babu Moger 
Reviewed-by: Shaopeng Tan 
Tested-by: Peter Newman 
Tested-by: Shaopeng Tan 
Tested-by: Amit Singh Tomar  # arm64
Tested-by: Shanker Donthineni  # arm64
Tested-by: Babu Moger 
Link: https://lore.kernel.org/r/20250311183715.16445-28-james.morse@arm.com

x86/resctrl: Make resctrl_arch_pseudo_lock_fn() take a plr

2025-03-12T11:24:33+00:00

resctrl_arch_pseudo_lock_fn() has architecture specific behaviour,
and takes a struct rdtgroup as an argument.

After the filesystem code moves to /fs/, the definition of struct
rdtgroup will not be available to the architecture code.

The only reason resctrl_arch_pseudo_lock_fn() wants the rdtgroup is
for the CLOSID. Embed that in the pseudo_lock_region as a closid,
and move the definition of struct pseudo_lock_region to resctrl.h.

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 
Reviewed-by: Babu Moger 
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 
Link: https://lore.kernel.org/r/20250311183715.16445-27-james.morse@arm.com

x86/resctrl: Make prefetch_disable_bits belong to the arch code

2025-03-12T11:24:30+00:00

prefetch_disable_bits is set by rdtgroup_locksetup_enter() from a value
provided by the architecture, but is largely read by other architecture
helpers.

Make resctrl_arch_get_prefetch_disable_bits() set prefetch_disable_bits so
that it can be isolated to arch-code from where the other arch-code helpers
can use its cached value.

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 
Reviewed-by: Babu Moger 
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 
Link: https://lore.kernel.org/r/20250311183715.16445-26-james.morse@arm.com

x86/resctrl: Allow an architecture to disable pseudo lock

2025-03-12T11:24:25+00:00

Pseudo-lock relies on knowledge of the micro-architecture to disable
prefetchers etc.

On arm64 these controls are typically secure only, meaning Linux can't access
them. Arm's cache-lockdown feature works in a very different way. Resctrl's
pseudo-lock isn't going to be used on arm64 platforms.

Add a Kconfig symbol that can be selected by the architecture. This enables or
disables building of the pseudo_lock.c file, and replaces the functions with
stubs. An additional IS_ENABLED() check is needed in rdtgroup_mode_write() so
that attempting to enable pseudo-lock reports an "Unknown or unsupported mode"
to user-space via the last_cmd_status file.

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 
Reviewed-by: Babu Moger 
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 
Link: https://lore.kernel.org/r/20250311183715.16445-25-james.morse@arm.com

x86/resctrl: Add resctrl_arch_ prefix to pseudo lock functions

2025-03-12T11:24:22+00:00

resctrl's pseudo lock has some copy-to-cache and measurement functions that
are micro-architecture specific.

For example, pseudo_lock_fn() is not at all portable.

Label these 'resctrl_arch_' so they stay under /arch/x86.  To expose these
functions to the filesystem code they need an entry in a header file, and
can't be marked static.

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 
Reviewed-by: Babu Moger 
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 
Link: https://lore.kernel.org/r/20250311183715.16445-24-james.morse@arm.com