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resctrl reads rdt_alloc_capable or rdt_mon_capable to determine whether any of
the resources support the corresponding features. resctrl also uses the
static keys that affect the architecture's context-switch code to determine the
same thing.
This forces another architecture to have the same static keys.
As the static key is enabled based on the capable flag, and none of the
filesystem uses of these are in the scheduler path, move the capable flags
behind helpers, and use these in the filesystem code instead of the static key.
After this change, only the architecture code manages and uses the static keys
to ensure __resctrl_sched_in() does not need runtime checks.
This avoids multiple architectures having to define the same static keys.
Cases where the static key implicitly tested if the resctrl filesystem was
mounted all have an explicit check now.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-20-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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rdt_enable_key is switched when resctrl is mounted. It was also previously used
to prevent a second mount of the filesystem.
Any other architecture that wants to support resctrl has to provide identical
static keys.
Now that there are helpers for enabling and disabling the alloc/mon keys,
resctrl doesn't need to switch this extra key, it can be done by the arch code.
Use the static-key increment and decrement helpers, and change resctrl to
ensure the calls are balanced.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-19-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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resctrl enables three static keys depending on the features it has enabled.
Another architecture's context switch code may look different, any static keys
that control it should be buried behind helpers.
Move the alloc/mon logic into arch-specific helpers as a preparatory step for
making the rdt_enable_key's status something the arch code decides.
This means other architectures don't have to mirror the static keys.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-18-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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Depending on the number of monitors available, Arm's MPAM may need to
allocate a monitor prior to reading the counter value. Allocating a
contended resource may involve sleeping.
__check_limbo() and mon_event_count() each make multiple calls to
resctrl_arch_rmid_read(), to avoid extra work on contended systems,
the allocation should be valid for multiple invocations of
resctrl_arch_rmid_read().
The memory or hardware allocated is not specific to a domain.
Add arch hooks for this allocation, which need calling before
resctrl_arch_rmid_read(). The allocated monitor is passed to
resctrl_arch_rmid_read(), then freed again afterwards. The helper
can be called on any CPU, and can sleep.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-16-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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When switching tasks, the CLOSID and RMID that the new task should use
are stored in struct task_struct. For x86 the CLOSID known by resctrl,
the value in task_struct, and the value written to the CPU register are
all the same thing.
MPAM's CPU interface has two different PARTIDs - one for data accesses
the other for instruction fetch. Storing resctrl's CLOSID value in
struct task_struct implies the arch code knows whether resctrl is using
CDP.
Move the matching and setting of the struct task_struct properties to
use helpers. This allows arm64 to store the hardware format of the
register, instead of having to convert it each time.
__rdtgroup_move_task()s use of READ_ONCE()/WRITE_ONCE() ensures torn
values aren't seen as another CPU may schedule the task being moved
while the value is being changed. MPAM has an additional corner-case
here as the PMG bits extend the PARTID space.
If the scheduler sees a new-CLOSID but old-RMID, the task will dirty an
RMID that the limbo code is not watching causing an inaccurate count.
x86's RMID are independent values, so the limbo code will still be
watching the old-RMID in this circumstance.
To avoid this, arm64 needs both the CLOSID/RMID WRITE_ONCE()d together.
Both values must be provided together.
Because MPAM's RMID values are not unique, the CLOSID must be provided
when matching the RMID.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-12-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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x86 systems identify traffic using the CLOSID and RMID. The CLOSID is
used to lookup the control policy, the RMID is used for monitoring. For
x86 these are independent numbers.
Arm's MPAM has equivalent features PARTID and PMG, where the PARTID is
used to lookup the control policy. The PMG in contrast is a small number
of bits that are used to subdivide PARTID when monitoring. The
cache-occupancy monitors require the PARTID to be specified when
monitoring.
This means MPAM's PMG field is not unique. There are multiple PMG-0, one
per allocated CLOSID/PARTID. If PMG is treated as equivalent to RMID, it
cannot be allocated as an independent number. Bitmaps like rmid_busy_llc
need to be sized by the number of unique entries for this resource.
Treat the combined CLOSID and RMID as an index, and provide architecture
helpers to pack and unpack an index. This makes the MPAM values unique.
The domain's rmid_busy_llc and rmid_ptrs[] are then sized by index, as
are domain mbm_local[] and mbm_total[].
x86 can ignore the CLOSID field when packing and unpacking an index, and
report as many indexes as RMID.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Babu Moger <babu.moger@amd.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-7-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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x86's RMID are independent of the CLOSID. An RMID can be allocated,
used and freed without considering the CLOSID.
MPAM's equivalent feature is PMG, which is not an independent number,
it extends the CLOSID/PARTID space. For MPAM, only PMG-bits worth of
'RMID' can be allocated for a single CLOSID.
i.e. if there is 1 bit of PMG space, then each CLOSID can have two
monitor groups.
To allow resctrl to disambiguate RMID values for different CLOSID,
everything in resctrl that keeps an RMID value needs to know the CLOSID
too. This will always be ignored on x86.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Xin Hao <xhao@linux.alibaba.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Peter Newman <peternewman@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Tested-by: Carl Worth <carl@os.amperecomputing.com> # arm64
Link: https://lore.kernel.org/r/20240213184438.16675-6-james.morse@arm.com
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
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The implementation of 'current' on x86 is very intentionally special: it
is a very common thing to look up, and it uses 'this_cpu_read_stable()'
to get the current thread pointer efficiently from per-cpu storage.
And the keyword in there is 'stable': the current thread pointer never
changes as far as a single thread is concerned. Even if when a thread
is preempted, or moved to another CPU, or even across an explicit call
'schedule()' that thread will still have the same value for 'current'.
It is, after all, the kernel base pointer to thread-local storage.
That's why it's stable to begin with, but it's also why it's important
enough that we have that special 'this_cpu_read_stable()' access for it.
So this is all done very intentionally to allow the compiler to treat
'current' as a value that never visibly changes, so that the compiler
can do CSE and combine multiple different 'current' accesses into one.
However, there is obviously one very special situation when the
currently running thread does actually change: inside the scheduler
itself.
So the scheduler code paths are special, and do not have a 'current'
thread at all. Instead there are _two_ threads: the previous and the
next thread - typically called 'prev' and 'next' (or prev_p/next_p)
internally.
So this is all actually quite straightforward and simple, and not all
that complicated.
Except for when you then have special code that is run in scheduler
context, that code then has to be aware that 'current' isn't really a
valid thing. Did you mean 'prev'? Did you mean 'next'?
In fact, even if then look at the code, and you use 'current' after the
new value has been assigned to the percpu variable, we have explicitly
told the compiler that 'current' is magical and always stable. So the
compiler is quite free to use an older (or newer) value of 'current',
and the actual assignment to the percpu storage is not relevant even if
it might look that way.
Which is exactly what happened in the resctl code, that blithely used
'current' in '__resctrl_sched_in()' when it really wanted the new
process state (as implied by the name: we're scheduling 'into' that new
resctl state). And clang would end up just using the old thread pointer
value at least in some configurations.
This could have happened with gcc too, and purely depends on random
compiler details. Clang just seems to have been more aggressive about
moving the read of the per-cpu current_task pointer around.
The fix is trivial: just make the resctl code adhere to the scheduler
rules of using the prev/next thread pointer explicitly, instead of using
'current' in a situation where it just wasn't valid.
That same code is then also used outside of the scheduler context (when
a thread resctl state is explicitly changed), and then we will just pass
in 'current' as that pointer, of course. There is no ambiguity in that
case.
The fix may be trivial, but noticing and figuring out what went wrong
was not. The credit for that goes to Stephane Eranian.
Reported-by: Stephane Eranian <eranian@google.com>
Link: https://lore.kernel.org/lkml/20230303231133.1486085-1-eranian@google.com/
Link: https://lore.kernel.org/lkml/alpine.LFD.2.01.0908011214330.3304@localhost.localdomain/
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Tested-by: Stephane Eranian <eranian@google.com>
Tested-by: Babu Moger <babu.moger@amd.com>
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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msr-index.h should contain all MSRs for easier grepping for MSR numbers
when dealing with unchecked MSR access warnings, for example.
Move the resctrl ones. Prefix IA32_PQR_ASSOC with "MSR_" while at it.
No functional changes.
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20221106212923.20699-1-bp@alien8.de
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resctrl_cqm_threshold is stored in a hardware specific chunk size,
but exposed to user-space as bytes.
This means the filesystem parts of resctrl need to know how the hardware
counts, to convert the user provided byte value to chunks. The interface
between the architecture's resctrl code and the filesystem ought to
treat everything as bytes.
Change the unit of resctrl_cqm_threshold to bytes. resctrl_arch_rmid_read()
still returns its value in chunks, so this needs converting to bytes.
As all the users have been touched, rename the variable to
resctrl_rmid_realloc_threshold, which describes what the value is for.
Neither r->num_rmid nor hw_res->mon_scale are guaranteed to be a power
of 2, so the existing code introduces a rounding error from resctrl's
theoretical fraction of the cache usage. This behaviour is kept as it
ensures the user visible value matches the value read from hardware
when the rmid will be reallocated.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jamie Iles <quic_jiles@quicinc.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Tested-by: Xin Hao <xhao@linux.alibaba.com>
Tested-by: Shaopeng Tan <tan.shaopeng@fujitsu.com>
Tested-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20220902154829.30399-20-james.morse@arm.com
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A CPU's current task can have its {closid, rmid} fields read locally
while they are being concurrently written to from another CPU.
This can happen anytime __resctrl_sched_in() races with either
__rdtgroup_move_task() or rdt_move_group_tasks().
Prevent load / store tearing for those accesses by giving them the
READ_ONCE() / WRITE_ONCE() treatment.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/9921fda88ad81afb9885b517fbe864a2bc7c35a9.1608243147.git.reinette.chatre@intel.com
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The function determining a platform's support and properties of cache
occupancy and memory bandwidth monitoring (properties of
X86_FEATURE_CQM_LLC) can be found among the common CPU code. After
the feature's properties is populated in the per-CPU data the resctrl
subsystem is the only consumer (via boot_cpu_data).
Move the function that obtains the CPU information used by resctrl to
the resctrl subsystem and rename it from init_cqm() to
resctrl_cpu_detect(). The function continues to be called from the
common CPU code. This move is done in preparation of the addition of some
vendor specific code.
No functional change.
Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/38433b99f9d16c8f4ee796f8cc42b871531fa203.1588715690.git.reinette.chatre@intel.com
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asm/resctrl_sched.h is dedicated to the code used for configuration
of the CPU resource control state when a task is scheduled.
Rename resctrl_sched.h to resctrl.h in preparation of additions that
will no longer make this file dedicated to work done during scheduling.
No functional change.
Suggested-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/6914e0ef880b539a82a6d889f9423496d471ad1d.1588715690.git.reinette.chatre@intel.com
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