linux-stable.git/arch/x86/kernel/itmt.c, branch linux-rolling-stable

x86/itmt: Add debugfs file to show core priorities

2025-07-07T20:35:51+00:00

Multiple drivers can report priorities to ITMT. To aid in debugging
any issues with the values reported by drivers introduce a debugfs
file to read out the values.

Signed-off-by: Mario Limonciello 
Signed-off-by: Borislav Petkov (AMD) 
Acked-by: Ilpo Järvinen 
Link: https://lore.kernel.org/20250609200518.3616080-14-superm1@kernel.org

x86/itmt: Move the "sched_itmt_enabled" sysctl to debugfs

2025-01-13T13:10:24+00:00

"sched_itmt_enabled" was only introduced as a debug toggle for any funky
ITMT behavior. Move the sysctl controlled from
"/proc/sys/kernel/sched_itmt_enabled" to debugfs at
"/sys/kernel/debug/x86/sched_itmt_enabled" with a notable change that a
cat on the file will return "Y" or "N" instead of "1" or "0" to
indicate that feature is enabled or disabled respectively. Either "0" or
"N" (or any string that kstrtobool() interprets as false) can be written
to the file will disable the feature, and writing  either "1" or "Y" (or
any string that kstrtobool() interprets as true) will enable it back
when the platform supports ITMT ranking.

Since ITMT is x86 specific (and PowerPC uses SD_ASYM_PACKING too), the
toggle was moved to "/sys/kernel/debug/x86/" as opposed to
"/sys/kernel/debug/sched/"

Suggested-by: Peter Zijlstra 
Signed-off-by: K Prateek Nayak 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Tim Chen 
Link: https://lore.kernel.org/r/20241223043407.1611-4-kprateek.nayak@amd.com

x86/itmt: Use guard() for itmt_update_mutex

2025-01-13T13:10:23+00:00

Use guard() for itmt_update_mutex which avoids the extra mutex_unlock()
in the bailout and return paths.

Signed-off-by: K Prateek Nayak 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Tim Chen 
Link: https://lore.kernel.org/r/20241223043407.1611-3-kprateek.nayak@amd.com

x86/itmt: Convert "sysctl_sched_itmt_enabled" to boolean

2025-01-13T13:10:23+00:00

In preparation to move "sysctl_sched_itmt_enabled" to debugfs, convert
the unsigned int to bool since debugfs readily exposes boolean fops
primitives (debugfs_read_file_bool, debugfs_write_file_bool) which can
streamline the conversion.

Since the current ctl_table initializes extra1 and extra2 to SYSCTL_ZERO
and SYSCTL_ONE respectively, the value of "sysctl_sched_itmt_enabled"
can only be 0 or 1 and this datatype conversion should not cause any
functional changes.

Signed-off-by: K Prateek Nayak 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Tim Chen 
Link: https://lore.kernel.org/r/20241223043407.1611-2-kprateek.nayak@amd.com

sysctl: treewide: constify the ctl_table argument of proc_handlers

2024-07-24T18:59:29+00:00

const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: Thomas Weißschuh 
Signed-off-by: Thomas Weißschuh 
Co-developed-by: Joel Granados 
Signed-off-by: Joel Granados

arch/x86: Remove now superfluous sentinel elem from ctl_table arrays

2023-10-10T22:22:02+00:00

This commit comes at the tail end of a greater effort to remove the
empty elements at the end of the ctl_table arrays (sentinels) which
will reduce the overall build time size of the kernel and run time
memory bloat by ~64 bytes per sentinel (further information Link :
https://lore.kernel.org/all/ZO5Yx5JFogGi%2FcBo@bombadil.infradead.org/)

Remove sentinel element from sld_sysctl and itmt_kern_table. This
removal is safe because register_sysctl_init and register_sysctl
implicitly use the array size in addition to checking for the sentinel.

Reviewed-by: Ingo Molnar 
Acked-by: Dave Hansen  # for x86
Signed-off-by: Joel Granados 
Signed-off-by: Luis Chamberlain

x86/sched/itmt: Give all SMT siblings of a core the same priority

2023-05-08T08:58:38+00:00

X86 does not have the SD_ASYM_PACKING flag in the SMT domain. The scheduler
knows how to handle SMT and non-SMT cores of different priority. There is
no reason for SMT siblings of a core to have different priorities.

Signed-off-by: Ricardo Neri 
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Len Brown 
Tested-by: Zhang Rui 
Link: https://lore.kernel.org/r/20230406203148.19182-12-ricardo.neri-calderon@linux.intel.com

x86: Simplify one-level sysctl registration for itmt_kern_table

2023-03-22T18:47:21+00:00

There is no need to declare an extra tables to just create directory,
this can be easily be done with a prefix path with register_sysctl().

Simplify this registration.

Signed-off-by: Luis Chamberlain 
Signed-off-by: Dave Hansen 
Link: https://lore.kernel.org/all/20230310233248.3965389-3-mcgrof%40kernel.org

x86/sched: Decrease further the priorities of SMT siblings

2021-10-05T13:51:59+00:00

When scheduling, it is better to prefer a separate physical core rather
than the SMT sibling of a high priority core. The existing formula to
compute priorities takes such fact in consideration. There may exist,
however, combinations of priorities (i.e., maximum frequencies) in which
the priority of high-numbered SMT siblings of high-priority cores collides
with the priority of low-numbered SMT siblings of low-priority cores.

Consider for instance an SMT2 system with CPUs [0, 1] with priority 60 and
[2, 3] with priority 30(CPUs in brackets are SMT siblings. In such a case,
the resulting priorities would be [120, 60], [60, 30]. Thus, to ensure
that CPU2 has higher priority than CPU1, divide the raw priority by the
squared SMT iterator. The resulting priorities are [120, 30]. [60, 15].

Originally-by: Len Brown 
Signed-off-by: Len Brown 
Signed-off-by: Ricardo Neri 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lkml.kernel.org/r/20210911011819.12184-2-ricardo.neri-calderon@linux.intel.com

sysctl: pass kernel pointers to ->proc_handler

2020-04-27T06:07:40+00:00

Instead of having all the sysctl handlers deal with user pointers, which
is rather hairy in terms of the BPF interaction, copy the input to and
from  userspace in common code.  This also means that the strings are
always NUL-terminated by the common code, making the API a little bit
safer.

As most handler just pass through the data to one of the common handlers
a lot of the changes are mechnical.

Signed-off-by: Christoph Hellwig 
Acked-by: Andrey Ignatov 
Signed-off-by: Al Viro