linux.git/arch/x86/kernel/cpu/resctrl, branch v5.11

x86/resctrl: Don't move a task to the same resource group

2021-01-08T08:08:03+00:00

Shakeel Butt reported in [1] that a user can request a task to be moved
to a resource group even if the task is already in the group. It just
wastes time to do the move operation which could be costly to send IPI
to a different CPU.

Add a sanity check to ensure that the move operation only happens when
the task is not already in the resource group.

[1] https://lore.kernel.org/lkml/CALvZod7E9zzHwenzf7objzGKsdBmVwTgEJ0nPgs0LUFU3SN5Pw@mail.gmail.com/

Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files")
Reported-by: Shakeel Butt 
Signed-off-by: Fenghua Yu 
Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov 
Reviewed-by: Tony Luck 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/962ede65d8e95be793cb61102cca37f7bb018e66.1608243147.git.reinette.chatre@intel.com

x86/resctrl: Use an IPI instead of task_work_add() to update PQR_ASSOC MSR

2021-01-08T08:03:36+00:00

Currently, when moving a task to a resource group the PQR_ASSOC MSR is
updated with the new closid and rmid in an added task callback. If the
task is running, the work is run as soon as possible. If the task is not
running, the work is executed later in the kernel exit path when the
kernel returns to the task again.

Updating the PQR_ASSOC MSR as soon as possible on the CPU a moved task
is running is the right thing to do. Queueing work for a task that is
not running is unnecessary (the PQR_ASSOC MSR is already updated when
the task is scheduled in) and causing system resource waste with the way
in which it is implemented: Work to update the PQR_ASSOC register is
queued every time the user writes a task id to the "tasks" file, even if
the task already belongs to the resource group.

This could result in multiple pending work items associated with a
single task even if they are all identical and even though only a single
update with most recent values is needed. Specifically, even if a task
is moved between different resource groups while it is sleeping then it
is only the last move that is relevant but yet a work item is queued
during each move.

This unnecessary queueing of work items could result in significant
system resource waste, especially on tasks sleeping for a long time.
For example, as demonstrated by Shakeel Butt in [1] writing the same
task id to the "tasks" file can quickly consume significant memory. The
same problem (wasted system resources) occurs when moving a task between
different resource groups.

As pointed out by Valentin Schneider in [2] there is an additional issue
with the way in which the queueing of work is done in that the task_struct
update is currently done after the work is queued, resulting in a race with
the register update possibly done before the data needed by the update is
available.

To solve these issues, update the PQR_ASSOC MSR in a synchronous way
right after the new closid and rmid are ready during the task movement,
only if the task is running. If a moved task is not running nothing
is done since the PQR_ASSOC MSR will be updated next time the task is
scheduled. This is the same way used to update the register when tasks
are moved as part of resource group removal.

[1] https://lore.kernel.org/lkml/CALvZod7E9zzHwenzf7objzGKsdBmVwTgEJ0nPgs0LUFU3SN5Pw@mail.gmail.com/
[2] https://lore.kernel.org/lkml/20201123022433.17905-1-valentin.schneider@arm.com

 [ bp: Massage commit message and drop the two update_task_closid_rmid()
   variants. ]

Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files")
Reported-by: Shakeel Butt 
Reported-by: Valentin Schneider 
Signed-off-by: Fenghua Yu 
Signed-off-by: Reinette Chatre 
Signed-off-by: Borislav Petkov 
Reviewed-by: Tony Luck 
Reviewed-by: James Morse 
Reviewed-by: Valentin Schneider 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/17aa2fb38fc12ce7bb710106b3e7c7b45acb9e94.1608243147.git.reinette.chatre@intel.com

Merge branch 'akpm' (patches from Andrew)

2020-12-15T20:53:37+00:00

Merge misc updates from Andrew Morton:

 - a few random little subsystems

 - almost all of the MM patches which are staged ahead of linux-next
   material. I'll trickle to post-linux-next work in as the dependents
   get merged up.

Subsystems affected by this patch series: kthread, kbuild, ide, ntfs,
ocfs2, arch, and mm (slab-generic, slab, slub, dax, debug, pagecache,
gup, swap, shmem, memcg, pagemap, mremap, hmm, vmalloc, documentation,
kasan, pagealloc, memory-failure, hugetlb, vmscan, z3fold, compaction,
oom-kill, migration, cma, page-poison, userfaultfd, zswap, zsmalloc,
uaccess, zram, and cleanups).

* emailed patches from Andrew Morton : (200 commits)
  mm: cleanup kstrto*() usage
  mm: fix fall-through warnings for Clang
  mm: slub: convert sysfs sprintf family to sysfs_emit/sysfs_emit_at
  mm: shmem: convert shmem_enabled_show to use sysfs_emit_at
  mm:backing-dev: use sysfs_emit in macro defining functions
  mm: huge_memory: convert remaining use of sprintf to sysfs_emit and neatening
  mm: use sysfs_emit for struct kobject * uses
  mm: fix kernel-doc markups
  zram: break the strict dependency from lzo
  zram: add stat to gather incompressible pages since zram set up
  zram: support page writeback
  mm/process_vm_access: remove redundant initialization of iov_r
  mm/zsmalloc.c: rework the list_add code in insert_zspage()
  mm/zswap: move to use crypto_acomp API for hardware acceleration
  mm/zswap: fix passing zero to 'PTR_ERR' warning
  mm/zswap: make struct kernel_param_ops definitions const
  userfaultfd/selftests: hint the test runner on required privilege
  userfaultfd/selftests: fix retval check for userfaultfd_open()
  userfaultfd/selftests: always dump something in modes
  userfaultfd: selftests: make __{s,u}64 format specifiers portable
  ...

mremap: don't allow MREMAP_DONTUNMAP on special_mappings and aio

2020-12-15T20:13:41+00:00

As kernel expect to see only one of such mappings, any further operations
on the VMA-copy may be unexpected by the kernel.  Maybe it's being on the
safe side, but there doesn't seem to be any expected use-case for this, so
restrict it now.

Link: https://lkml.kernel.org/r/20201013013416.390574-4-dima@arista.com
Fixes: commit e346b3813067 ("mm/mremap: add MREMAP_DONTUNMAP to mremap()")
Signed-off-by: Dmitry Safonov 
Cc: Alexander Viro 
Cc: Andy Lutomirski 
Cc: Brian Geffon 
Cc: Catalin Marinas 
Cc: Dan Carpenter 
Cc: Dan Williams 
Cc: Dave Jiang 
Cc: Hugh Dickins 
Cc: Ingo Molnar 
Cc: Jason Gunthorpe 
Cc: John Hubbard 
Cc: "Kirill A. Shutemov" 
Cc: Mike Kravetz 
Cc: Minchan Kim 
Cc: Ralph Campbell 
Cc: Russell King 
Cc: Thomas Bogendoerfer 
Cc: Thomas Gleixner 
Cc: Vishal Verma 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge tag 'x86_cache_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-12-14T21:53:17+00:00

Pull x86 cache resource control updates from Borislav Petkov:

 - add logic to correct MBM total and local values fixing errata SKX99
   and BDF102 (Fenghua Yu)

 - cleanups

* tag 'x86_cache_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/resctrl: Clean up unused function parameter in rmdir path
  x86/resctrl: Constify kernfs_ops
  x86/resctrl: Correct MBM total and local values
  Documentation/x86: Rename resctrl_ui.rst and add two errata to the file

x86/resctrl: Fix incorrect local bandwidth when mba_sc is enabled

2020-12-10T16:52:37+00:00

The MBA software controller (mba_sc) is a feedback loop which
periodically reads MBM counters and tries to restrict the bandwidth
below a user-specified value. It tags along the MBM counter overflow
handler to do the updates with 1s interval in mbm_update() and
update_mba_bw().

The purpose of mbm_update() is to periodically read the MBM counters to
make sure that the hardware counter doesn't wrap around more than once
between user samplings. mbm_update() calls __mon_event_count() for local
bandwidth updating when mba_sc is not enabled, but calls mbm_bw_count()
instead when mba_sc is enabled. __mon_event_count() will not be called
for local bandwidth updating in MBM counter overflow handler, but it is
still called when reading MBM local bandwidth counter file
'mbm_local_bytes', the call path is as below:

  rdtgroup_mondata_show()
    mon_event_read()
      mon_event_count()
        __mon_event_count()

In __mon_event_count(), m->chunks is updated by delta chunks which is
calculated from previous MSR value (m->prev_msr) and current MSR value.
When mba_sc is enabled, m->chunks is also updated in mbm_update() by
mistake by the delta chunks which is calculated from m->prev_bw_msr
instead of m->prev_msr. But m->chunks is not used in update_mba_bw() in
the mba_sc feedback loop.

When reading MBM local bandwidth counter file, m->chunks was changed
unexpectedly by mbm_bw_count(). As a result, the incorrect local
bandwidth counter which calculated from incorrect m->chunks is shown to
the user.

Fix this by removing incorrect m->chunks updating in mbm_bw_count() in
MBM counter overflow handler, and always calling __mon_event_count() in
mbm_update() to make sure that the hardware local bandwidth counter
doesn't wrap around.

Test steps:
  # Run workload with aggressive memory bandwidth (e.g., 10 GB/s)
  git clone https://github.com/intel/intel-cmt-cat && cd intel-cmt-cat
  && make
  ./tools/membw/membw -c 0 -b 10000 --read

  # Enable MBA software controller
  mount -t resctrl resctrl -o mba_MBps /sys/fs/resctrl

  # Create control group c1
  mkdir /sys/fs/resctrl/c1

  # Set MB throttle to 6 GB/s
  echo "MB:0=6000;1=6000" > /sys/fs/resctrl/c1/schemata

  # Write PID of the workload to tasks file
  echo `pidof membw` > /sys/fs/resctrl/c1/tasks

  # Read local bytes counters twice with 1s interval, the calculated
  # local bandwidth is not as expected (approaching to 6 GB/s):
  local_1=`cat /sys/fs/resctrl/c1/mon_data/mon_L3_00/mbm_local_bytes`
  sleep 1
  local_2=`cat /sys/fs/resctrl/c1/mon_data/mon_L3_00/mbm_local_bytes`
  echo "local b/w (bytes/s):" `expr $local_2 - $local_1`

Before fix:
  local b/w (bytes/s): 11076796416

After fix:
  local b/w (bytes/s): 5465014272

Fixes: ba0f26d8529c (x86/intel_rdt/mba_sc: Prepare for feedback loop)
Signed-off-by: Xiaochen Shen 
Signed-off-by: Borislav Petkov 
Reviewed-by: Tony Luck 
Cc: 
Link: https://lkml.kernel.org/r/1607063279-19437-1-git-send-email-xiaochen.shen@intel.com

x86/resctrl: Clean up unused function parameter in rmdir path

2020-12-01T17:06:35+00:00

Commit

  fd8d9db3559a ("x86/resctrl: Remove superfluous kernfs_get() calls to prevent refcount leak")

removed superfluous kernfs_get() calls in rdtgroup_ctrl_remove() and
rdtgroup_rmdir_ctrl(). That change resulted in an unused function
parameter to these two functions.

Clean up the unused function parameter in rdtgroup_ctrl_remove(),
rdtgroup_rmdir_mon() and their callers rdtgroup_rmdir_ctrl() and
rdtgroup_rmdir().

Signed-off-by: Xiaochen Shen 
Signed-off-by: Borislav Petkov 
Reviewed-by: Reinette Chatre 
Link: https://lkml.kernel.org/r/1606759618-13181-1-git-send-email-xiaochen.shen@intel.com

Merge tag 'v5.10-rc6' into x86/cache

2020-12-01T17:01:27+00:00

Merge -rc6 tag to pick up dependent changes.

Signed-off-by: Borislav Petkov

x86/resctrl: Fix AMD L3 QOS CDP enable/disable

2020-12-01T16:53:31+00:00

When the AMD QoS feature CDP (code and data prioritization) is enabled
or disabled, the CDP bit in MSR 0000_0C81 is written on one of the CPUs
in an L3 domain (core complex). That is not correct - the CDP bit needs
to be updated on all the logical CPUs in the domain.

This was not spelled out clearly in the spec earlier. The specification
has been updated and the updated document, "AMD64 Technology Platform
Quality of Service Extensions Publication # 56375 Revision: 1.02 Issue
Date: October 2020" is available now. Refer the section: Code and Data
Prioritization.

Fix the issue by adding a new flag arch_has_per_cpu_cfg in rdt_cache
data structure.

The documentation can be obtained at:
https://developer.amd.com/wp-content/resources/56375.pdf
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537

 [ bp: Massage commit message. ]

Fixes: 4d05bf71f157 ("x86/resctrl: Introduce AMD QOS feature")
Signed-off-by: Babu Moger 
Signed-off-by: Borislav Petkov 
Reviewed-by: Reinette Chatre 
Link: https://lkml.kernel.org/r/160675180380.15628.3309402017215002347.stgit@bmoger-ubuntu

x86/resctrl: Add necessary kernfs_put() calls to prevent refcount leak

2020-11-24T11:13:37+00:00

On resource group creation via a mkdir an extra kernfs_node reference is
obtained by kernfs_get() to ensure that the rdtgroup structure remains
accessible for the rdtgroup_kn_unlock() calls where it is removed on
deletion. Currently the extra kernfs_node reference count is only
dropped by kernfs_put() in rdtgroup_kn_unlock() while the rdtgroup
structure is removed in a few other locations that lack the matching
reference drop.

In call paths of rmdir and umount, when a control group is removed,
kernfs_remove() is called to remove the whole kernfs nodes tree of the
control group (including the kernfs nodes trees of all child monitoring
groups), and then rdtgroup structure is freed by kfree(). The rdtgroup
structures of all child monitoring groups under the control group are
freed by kfree() in free_all_child_rdtgrp().

Before calling kfree() to free the rdtgroup structures, the kernfs node
of the control group itself as well as the kernfs nodes of all child
monitoring groups still take the extra references which will never be
dropped to 0 and the kernfs nodes will never be freed. It leads to
reference count leak and kernfs_node_cache memory leak.

For example, reference count leak is observed in these two cases:
  (1) mount -t resctrl resctrl /sys/fs/resctrl
      mkdir /sys/fs/resctrl/c1
      mkdir /sys/fs/resctrl/c1/mon_groups/m1
      umount /sys/fs/resctrl

  (2) mkdir /sys/fs/resctrl/c1
      mkdir /sys/fs/resctrl/c1/mon_groups/m1
      rmdir /sys/fs/resctrl/c1

The same reference count leak issue also exists in the error exit paths
of mkdir in mkdir_rdt_prepare() and rdtgroup_mkdir_ctrl_mon().

Fix this issue by following changes to make sure the extra kernfs_node
reference on rdtgroup is dropped before freeing the rdtgroup structure.
  (1) Introduce rdtgroup removal helper rdtgroup_remove() to wrap up
  kernfs_put() and kfree().

  (2) Call rdtgroup_remove() in rdtgroup removal path where the rdtgroup
  structure is about to be freed by kfree().

  (3) Call rdtgroup_remove() or kernfs_put() as appropriate in the error
  exit paths of mkdir where an extra reference is taken by kernfs_get().

Fixes: f3cbeacaa06e ("x86/intel_rdt/cqm: Add rmdir support")
Fixes: e02737d5b826 ("x86/intel_rdt: Add tasks files")
Fixes: 60cf5e101fd4 ("x86/intel_rdt: Add mkdir to resctrl file system")
Reported-by: Willem de Bruijn 
Signed-off-by: Xiaochen Shen 
Signed-off-by: Borislav Petkov 
Reviewed-by: Reinette Chatre 
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1604085088-31707-1-git-send-email-xiaochen.shen@intel.com