This reverts commit 76d3b851.

The returned value for check_tsc_warp() is useless now, remove it.
Signed-off-by: NJiufei Xue <jiufei.xue@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

This reverts commit cc4db268.

When we do hot-add and enable vCPU, the time inside the VM jumps and
then VM stucks.
The dmesg shows like this:
[   48.402948] CPU2 has been hot-added
[   48.413774] smpboot: Booting Node 0 Processor 2 APIC 0x2
[   48.415155] kvm-clock: cpu 2, msr 6b615081, secondary cpu clock
[   48.453690] TSC ADJUST compensate: CPU2 observed 139318776350 warp.  Adjust: 139318776350
[  102.060874] clocksource: timekeeping watchdog on CPU0: Marking clocksource 'tsc' as unstable because the skew is too large:
[  102.060874] clocksource:                       'kvm-clock' wd_now: 1cb1cfc4bf8 wd_last: 1be9588f1fe mask: ffffffffffffffff
[  102.060874] clocksource:                       'tsc' cs_now: 207d794f7e cs_last: 205a32697a mask: ffffffffffffffff
[  102.060874] tsc: Marking TSC unstable due to clocksource watchdog
[  102.070188] KVM setup async PF for cpu 2
[  102.071461] kvm-stealtime: cpu 2, msr 13ba95000
[  102.074530] Will online and init hotplugged CPU: 2

This is because the TSC for the newly added VCPU is initialized to 0
while others are ahead. Guest will do the TSC ADJUST compensate and
cause the time jumps.

Commit bd8fab39("KVM: x86: fix maintaining of kvm_clock stability
on guest CPU hotplug") can fix this problem.  However, the host kernel
version may be older, so do not ajust TSC if sync test fails, just mark
it unstable.
Signed-off-by: NJiufei Xue <jiufei.xue@linux.alibaba.com>
Reviewed-by: NJoseph Qi <joseph.qi@linux.alibaba.com>

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier.  The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
 - file had no licensing information it it.
 - file was a */uapi/* one with no licensing information in it,
 - file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne.  Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed.  Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
 - Files considered eligible had to be source code files.
 - Make and config files were included as candidates if they contained >5
   lines of source
 - File already had some variant of a license header in it (even if <5
   lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

 - when both scanners couldn't find any license traces, file was
   considered to have no license information in it, and the top level
   COPYING file license applied.

   For non */uapi/* files that summary was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0                                              11139

   and resulted in the first patch in this series.

   If that file was a */uapi/* path one, it was "GPL-2.0 WITH
   Linux-syscall-note" otherwise it was "GPL-2.0".  Results of that was:

   SPDX license identifier                            # files
   ---------------------------------------------------|-------
   GPL-2.0 WITH Linux-syscall-note                        930

   and resulted in the second patch in this series.

 - if a file had some form of licensing information in it, and was one
   of the */uapi/* ones, it was denoted with the Linux-syscall-note if
   any GPL family license was found in the file or had no licensing in
   it (per prior point).  Results summary:

   SPDX license identifier                            # files
   ---------------------------------------------------|------
   GPL-2.0 WITH Linux-syscall-note                       270
   GPL-2.0+ WITH Linux-syscall-note                      169
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause)    21
   ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)    17
   LGPL-2.1+ WITH Linux-syscall-note                      15
   GPL-1.0+ WITH Linux-syscall-note                       14
   ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause)    5
   LGPL-2.0+ WITH Linux-syscall-note                       4
   LGPL-2.1 WITH Linux-syscall-note                        3
   ((GPL-2.0 WITH Linux-syscall-note) OR MIT)              3
   ((GPL-2.0 WITH Linux-syscall-note) AND MIT)             1

   and that resulted in the third patch in this series.

 - when the two scanners agreed on the detected license(s), that became
   the concluded license(s).

 - when there was disagreement between the two scanners (one detected a
   license but the other didn't, or they both detected different
   licenses) a manual inspection of the file occurred.

 - In most cases a manual inspection of the information in the file
   resulted in a clear resolution of the license that should apply (and
   which scanner probably needed to revisit its heuristics).

 - When it was not immediately clear, the license identifier was
   confirmed with lawyers working with the Linux Foundation.

 - If there was any question as to the appropriate license identifier,
   the file was flagged for further research and to be revisited later
   in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights.  The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
 - a full scancode scan run, collecting the matched texts, detected
   license ids and scores
 - reviewing anything where there was a license detected (about 500+
   files) to ensure that the applied SPDX license was correct
 - reviewing anything where there was no detection but the patch license
   was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
   SPDX license was correct

This produced a worksheet with 20 files needing minor correction.  This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg.  Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected.  This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.)  Finally Greg ran the script using the .csv files to
generate the patches.
Reviewed-by: NKate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: NPhilippe Ombredanne <pombredanne@nexb.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Prior to the TSC ADJUST MSR being available, the method to set TSC's in
sync with each other naturally caused a small skew between cpu threads.
This was NOT a firmware bug at the time so introducing a whole avalanche
of alarming warning messages might cause unnecessary concern and customer
complaints. (Example: >3000 msgs in a 32 socket Skylake system.)

Simply report the warning condition, if possible do the necessary fixes,
and move on.
Signed-off-by: NMike Travis <mike.travis@hpe.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NDimitri Sivanich <dimitri.sivanich@hpe.com>
Reviewed-by: NRuss Anderson <russ.anderson@hpe.com>
Reviewed-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Andrew Banman <andrew.banman@hpe.com>
Cc: Bin Gao <bin.gao@linux.intel.com>
Link: https://lkml.kernel.org/r/20171012163202.175062400@stormcage.americas.sgi.com

If the TSC has already been determined to be unstable, then checking
TSC ADJUST values is a waste of time and generates unnecessary error
messages.
Signed-off-by: NMike Travis <mike.travis@hpe.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NDimitri Sivanich <dimitri.sivanich@hpe.com>
Reviewed-by: NRuss Anderson <russ.anderson@hpe.com>
Reviewed-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Andrew Banman <andrew.banman@hpe.com>
Cc: Bin Gao <bin.gao@linux.intel.com>
Link: https://lkml.kernel.org/r/20171012163202.060777495@stormcage.americas.sgi.com

Add a flag to indicate and process that TSC counters are on chassis
that reset at different times during system startup.  Therefore which
TSC ADJUST values should be zero is not predictable.
Signed-off-by: NMike Travis <mike.travis@hpe.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NDimitri Sivanich <dimitri.sivanich@hpe.com>
Reviewed-by: NRuss Anderson <russ.anderson@hpe.com>
Reviewed-by: NAndrew Banman <andrew.abanman@hpe.com>
Reviewed-by: NPeter Zijlstra <peterz@infradead.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Andrew Banman <andrew.banman@hpe.com>
Cc: Bin Gao <bin.gao@linux.intel.com>
Link: https://lkml.kernel.org/r/20171012163201.944370012@stormcage.americas.sgi.com

Now that all affected platforms have a microcode update; and we check
this and disable TSC_DEADLINE and print a microcode revision update
error if its too old, we can remove the TSC_ADJUST clamp.

This should help with systems where the second socket runs ahead of
the first socket and needs a negative adjustment. In this case we'd
hit the 0 clamp and give up for not achieving synchronization.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: kevin.b.stanton@intel.com
Link: http://lkml.kernel.org/r/20170531155306.100950003@infradead.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

When the TSC is marked reliable then the synchronization check is skipped,
but that also skips the TSC ADJUST sanitizing code. So on a machine with a
wreckaged BIOS the TSC deviation between CPUs might go unnoticed.

Let the TSC adjust sanitizing code run unconditionally and just skip the
expensive synchronization checks when TSC is marked reliable.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Olof Johansson <olof@lixom.net>
Link: http://lkml.kernel.org/r/20170209151231.491189912@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Adjust value 0x80000000 and other values larger than that render the TSC
deadline timer disfunctional.

We have not yet any information about this from Intel, but experimentation
clearly proves that this is a 32/64 bit and sign extension issue.

If adjust values larger than that are actually required, which might be the
case for physical CPU hotplug, then we need to disable the deadline timer
on the affected package/CPUs and use the local APIC timer instead.

That requires some surgery in the APIC setup code, so we just limit the
ADJUST register value into the known to work range for now and revisit this
when Intel comes forth with proper information.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Roland Scheidegger <rscheidegger_lists@hispeed.ch>
Cc: Bruce Schlobohm <bruce.schlobohm@intel.com>
Cc: Kevin Stanton <kevin.b.stanton@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>

Make it more obvious that the BIOS is screwed up.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Roland Scheidegger <rscheidegger_lists@hispeed.ch>
Cc: Bruce Schlobohm <bruce.schlobohm@intel.com>
Cc: Kevin Stanton <kevin.b.stanton@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>

Roland reported that his DELL T5810 sports a value add BIOS which
completely wreckages the TSC. The squirmware [(TM) Ingo Molnar] boots with
random negative TSC_ADJUST values, different on all CPUs. That renders the
TSC useless because the sycnchronization check fails.

Roland tested the new TSC_ADJUST mechanism. While it manages to readjust
the TSCs he needs to disable the TSC deadline timer, otherwise the machine
just stops booting.

Deeper investigation unearthed that the TSC deadline timer is sensitive to
the TSC_ADJUST value. Writing TSC_ADJUST to a negative value results in an
interrupt storm caused by the TSC deadline timer.

This does not make any sense and it's hard to imagine what kind of hardware
wreckage is behind that misfeature, but it's reliably reproducible on other
systems which have TSC_ADJUST and TSC deadline timer.

While it would be understandable that a big enough negative value which
moves the resulting TSC readout into the negative space could have the
described effect, this happens even with a adjust value of -1, which keeps
the TSC readout definitely in the positive space. The compare register for
the TSC deadline timer is set to a positive value larger than the TSC, but
despite not having reached the deadline the interrupt is raised
immediately. If this happens on the boot CPU, then the machine dies
silently because this setup happens before the NMI watchdog is armed.

Further experiments showed that any other adjustment of TSC_ADJUST works as
expected as long as it stays in the positive range. The direction of the
adjustment has no influence either. See the lkml link for further analysis.

Yet another proof for the theory that timers are designed by janitors and
the underlying (obviously undocumented) mechanisms which allow BIOSes to
wreckage them are considered a feature. Well done Intel - NOT!

To address this wreckage add the following sanity measures:

- If the TSC_ADJUST value on the boot cpu is not 0, set it to 0

- If the TSC_ADJUST value on any cpu is negative, set it to 0

- Prevent the cross package synchronization mechanism from setting negative
  TSC_ADJUST values.
Reported-and-tested-by: NRoland Scheidegger <rscheidegger_lists@hispeed.ch>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Bruce Schlobohm <bruce.schlobohm@intel.com>
Cc: Kevin Stanton <kevin.b.stanton@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Allen Hung <allen_hung@dell.com>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Some 'feature' BIOSes fiddle with the TSC_ADJUST register during
suspend/resume which renders the TSC unusable.

Add sanity checks into the resume path and restore the
original value if it was adjusted.
Reported-and-tested-by: NRoland Scheidegger <rscheidegger_lists@hispeed.ch>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Bruce Schlobohm <bruce.schlobohm@intel.com>
Cc: Kevin Stanton <kevin.b.stanton@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Allen Hung <allen_hung@dell.com>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161213131211.317654500@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

0-day testing encountered a NULL pointer dereference in a cpumask access
from tsc_store_and_check_tsc_adjust().

This happens when the function is called on the boot CPU and the topology
masks are not yet available due to CPUMASK_OFFSTACK=y.

Add a NULL pointer check for the mask pointer. If NULL it's safe to assume
that the CPU is the boot CPU and the first one in the package.

Fixes: 8b223bc7 ("x86/tsc: Store and check TSC ADJUST MSR")
Reported-by: Nkernel test robot <xiaolong.ye@intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Add the missing return statement to the inline stub
tsc_store_and_check_tsc_adjust() and add the other stubs to make a
SMP=y,TSC=n build happy.

While at it, remove the unused variable from the UP variant of
tsc_store_and_check_tsc_adjust().

Fixes: commit ba75fb646931 ("x86/tsc: Sync test only for the first cpu in a package")
Reported-by: Nkbuild test robot <fengguang.wu@intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

If the first CPU of a package comes online, it is necessary to test whether
the TSC is in sync with a CPU on some other package. When a deviation is
observed (time going backwards between the two CPUs) the TSC is marked
unstable, which is a problem on large machines as they have to fall back to
the HPET clocksource, which is insanely slow.

It has been attempted to compensate the TSC by adding the offset to the TSC
and writing it back some time ago, but this never was merged because it did
not turn out to be stable, especially not on older systems.

Modern systems have become more stable in that regard and the TSC_ADJUST
MSR allows us to compensate for the time deviation in a sane way. If it's
available allow up to three synchronization runs and if a time warp is
detected the starting CPU can compensate the time warp via the TSC_ADJUST
MSR and retry. If the third run still shows a deviation or when random time
warps are detected the test terminally fails.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134018.048237517@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

To allow TSC compensation cross nodes its necessary to know in which
direction the TSC warp was observed. Return the maximum observed value on
the calling CPU so the caller can determine the direction later.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.970859287@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Cleaning up the stop marker on the control CPU is wrong when we want to add
retry support. Move the cleanup to the starting CPU.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.892095627@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

If the TSC_ADJUST MSR is available all CPUs in a package are forced to the
same value. So TSCs cannot be out of sync when the first CPU in the package
was in sync.

That allows to skip the sync test for all CPUs except the first starting
CPU in a package.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.809901363@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

When entering idle, it's a good oportunity to verify that the TSC_ADJUST
MSR has not been tampered with (BIOS hiding SMM cycles). If tampering is
detected, emit a warning and restore it to the previous value.

This is especially important for machines, which mark the TSC reliable
because there is no watchdog clocksource available (SoCs).

This is not sufficient for HPC (NOHZ_FULL) situations where a CPU never
goes idle, but adding a timer to do the check periodically is not an option
either. On a machine, which has this issue, the check triggeres right
during boot, so there is a decent chance that the sysadmin will notice.

Rate limit the check to once per second and warn only once per cpu.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.732180441@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

The TSC_ADJUST MSR shows whether the TSC has been modified. This is helpful
in a two aspects:

1) It allows to detect BIOS wreckage, where SMM code tries to 'hide' the
   cycles spent by storing the TSC value at SMM entry and restoring it at
   SMM exit. On affected machines the TSCs run slowly out of sync up to the
   point where the clocksource watchdog (if available) detects it.

   The TSC_ADJUST MSR allows to detect the TSC modification before that and
   eventually restore it. This is also important for SoCs which have no
   watchdog clocksource and therefore TSC wreckage cannot be detected and
   acted upon.

2) All threads in a package are required to have the same TSC_ADJUST
   value. Broken BIOSes break that and as a result the TSC synchronization
   check fails.

   The TSC_ADJUST MSR allows to detect the deviation when a CPU comes
   online. If detected set it to the value of an already online CPU in the
   same package. This also allows to reduce the number of sync tests
   because with that in place the test is only required for the first CPU
   in a package.

   In principle all CPUs in a system should have the same TSC_ADJUST value
   even across packages, but with physical CPU hotplug this assumption is
   not true because the TSC starts with power on, so physical hotplug has
   to do some trickery to bring the TSC into sync with already running
   packages, which requires to use an TSC_ADJUST value different from CPUs
   which got powered earlier.

   A final enhancement is the opportunity to compensate for unsynced TSCs
   accross nodes at boot time and make the TSC usable that way. It won't
   help for TSCs which run apart due to frequency skew between packages,
   but this gets detected by the clocksource watchdog later.

The first step toward this is to store the TSC_ADJUST value of a starting
CPU and compare it with the value of an already online CPU in the same
package. If they differ, emit a warning and adjust it to the reference
value. The !SMP version just stores the boot value for later verification.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.655323776@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

If time warps can be observed then they should only ever be observed on one
CPU. If they are observed on both CPUs then the system is completely hosed.

Add a check for this condition and notify if it happens.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NIngo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/20161119134017.574838461@linutronix.deSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Using get_cycles was unnecessary: check_tsc_warp() is not called
on TSC-less systems. Replace rdtsc_barrier(); get_cycles() with
rdtsc_ordered().

While we're at it, make the somewhat more dangerous change of
removing barrier_before_rdtsc after RDTSC in the TSC warp check
code. This should be okay, though -- the vDSO TSC code doesn't
have that barrier, so, if removing the barrier from the warp
check would cause us to detect a warp that we otherwise wouldn't
detect, then we have a genuine bug.
Signed-off-by: NAndy Lutomirski <luto@kernel.org>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/387c4c3a75f875bcde6cd68cee013273a744f364.1434501121.git.luto@kernel.orgSigned-off-by: NIngo Molnar <mingo@kernel.org>

The former duplicate the functionalities of the latter but are
neither documented nor arch-independent.
Signed-off-by: NBartosz Golaszewski <bgolaszewski@baylibre.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Benoit Cousson <bcousson@baylibre.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jean Delvare <jdelvare@suse.de>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Drokin <oleg.drokin@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Link: http://lkml.kernel.org/r/1432645896-12588-9-git-send-email-bgolaszewski@baylibre.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

None of these files are actually using any __init type directives
and hence don't need to include <linux/init.h>.  Most are just a
left over from __devinit and __cpuinit removal, or simply due to
code getting copied from one driver to the next.

[ hpa: undid incorrect removal from arch/x86/kernel/head_32.S ]
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Link: http://lkml.kernel.org/r/1389054026-12947-1-git-send-email-paul.gortmaker@windriver.comSigned-off-by: NH. Peter Anvin <hpa@zytor.com>

The __cpuinit type of throwaway sections might have made sense
some time ago when RAM was more constrained, but now the savings
do not offset the cost and complications.  For example, the fix in
commit 5e427ec2 ("x86: Fix bit corruption at CPU resume time")
is a good example of the nasty type of bugs that can be created
with improper use of the various __init prefixes.

After a discussion on LKML[1] it was decided that cpuinit should go
the way of devinit and be phased out.  Once all the users are gone,
we can then finally remove the macros themselves from linux/init.h.

Note that some harmless section mismatch warnings may result, since
notify_cpu_starting() and cpu_up() are arch independent (kernel/cpu.c)
are flagged as __cpuinit  -- so if we remove the __cpuinit from
arch specific callers, we will also get section mismatch warnings.
As an intermediate step, we intend to turn the linux/init.h cpuinit
content into no-ops as early as possible, since that will get rid
of these warnings.  In any case, they are temporary and harmless.

This removes all the arch/x86 uses of the __cpuinit macros from
all C files.  x86 only had the one __CPUINIT used in assembly files,
and it wasn't paired off with a .previous or a __FINIT, so we can
delete it directly w/o any corresponding additional change there.

[1] https://lkml.org/lkml/2013/5/20/589

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Acked-by: NIngo Molnar <mingo@kernel.org>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NH. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>

For each logical CPU that is coming online, we spend 20msec for
checking the TSC synchronization. And as this is done
sequentially for each logical CPU boot, this time gets added up
depending on the number of logical CPU's supported by the
platform.

Minimize this by using the socket topology information.

If the target CPU coming online doesn't have any of its
core-siblings online, a timeout of 20msec will be used for the
TSC-warp measurement loop. Otherwise a smaller timeout of 2msec
will be used, as we have some information about this socket
already (and this information grows as we have more and more
logical-siblings in that socket).

Ideally we should be able to skip the TSC sync check on the
other core-siblings, if the first logical CPU in a socket passed
the sync test. But as the TSC is per-logical CPU and can
potentially be modified wrongly by the bios before the OS boot,
TSC sync test for smaller duration should be able to catch such
errors. Also this will catch the condition where all the cores
in the socket doesn't get reset at the same time.

For example, with this modification, time spent in TSC sync
checks on a 4 socket 10-core with HT system gets reduced from
1580msec to 212msec.
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: NArjan van de Ven <arjan@linux.intel.com>
Acked-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Jack Steiner <steiner@sgi.com>
Cc: venki@google.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1328581940.29790.20.camel@sbsiddha-desk.sc.intel.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

tsc=reliable boot parameter is supposed to skip all the TSC
stablility checks during boot time.

On a 8-socket system where we want to run an experiment with the
"tsc=reliable" boot option, TSC synchronization checks are not
getting skipped and marking the TSC as not stable.

Check for tsc_clocksource_reliable (which is set via
tsc=reliable or for platforms supporting synthetic TSC_RELIABLE
feature bit etc) and when set, skip the TSC synchronization
tests during boot.
Signed-off-by: NSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: NJohn Stultz <johnstul@us.ibm.com>
Tested-by: NSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1320446537.15071.14.camel@sbsiddha-desk.sc.intel.comSigned-off-by: NIngo Molnar <mingo@elte.hu>

Name space cleanup. No functional change.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: linux-arch@vger.kernel.org

Further name space cleanup. No functional change
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: linux-arch@vger.kernel.org

The raw_spin* namespace was taken by lockdep for the architecture
specific implementations. raw_spin_* would be the ideal name space for
the spinlocks which are not converted to sleeping locks in preempt-rt.

Linus suggested to convert the raw_ to arch_ locks and cleanup the
name space instead of using an artifical name like core_spin,
atomic_spin or whatever

No functional change.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Acked-by: NPeter Zijlstra <peterz@infradead.org>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Acked-by: NIngo Molnar <mingo@elte.hu>
Cc: linux-arch@vger.kernel.org

Limit the number of per cpu TSC sync messages by only printing
to the console if an error occurs, otherwise print as a DEBUG
message.

The info message "Skipping synchronization ..." is only printed
after the last cpu has booted.
Signed-off-by: NMike Travis <travis@sgi.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Roland Dreier <rdreier@cisco.com>
Cc: Randy Dunlap <rdunlap@xenotime.net>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <20091118002222.181053000@alcatraz.americas.sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

On modern systems, the kernel prints the message

    Skipping synchronization checks as TSC is reliable.

once for every non-boot CPU.

This gets kind of ridiculous on huge systems; for example, on a
64-thread system I was lucky enough to get:

    $ dmesg | grep 'TSC is reliable' | wc
         63     567    4221

There's no point to doing this for every CPU, since the code is
just checking the boot CPU anyway, so change this to a
printk_once() to make the message appears only once.
Signed-off-by: NRoland Dreier <rolandd@cisco.com>
LKML-Reference: <adazl8l2swc.fsf@cisco.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

 - remove unused define
 - make the lock variable definition stand out some more
 - convert KERN_* to pr_info() / pr_warning()

[ Impact: cleanup ]

LKML-Reference: <new-submission>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix incorrectly marked unstable TSC clock

Patch (commit 0d12cdd5 "sched: improve sched_clock() performance") has
a regression on one of the test systems here.

With the patch, I see:

 checking TSC synchronization [CPU#0 -> CPU#1]:
 Measured 28 cycles TSC warp between CPUs, turning off TSC clock.
 Marking TSC unstable due to check_tsc_sync_source failed

Whereas, without the patch syncs pass fine on all CPUs:

 checking TSC synchronization [CPU#0 -> CPU#1]: passed.

Due to this, TSC is marked unstable, when it is not actually unstable.
This is because syncs in check_tsc_wrap() goes away due to this commit.

As per the discussion on this thread, correct way to fix this is to add
explicit syncs as below?
Signed-off-by: NVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: Changes timebase calibration on Vmware.

Use the synthetic TSC_RELIABLE bit to workaround virtualization anomalies.

Virtual TSCs can be kept nearly in sync, but because the virtual TSC
offset is set by software, it's not perfect.  So, the TSC
synchronization test can fail. Even then the TSC can be used as a
clocksource since the VMware platform exports a reliable TSC to the
guest for timekeeping purposes. Use this bit to check if we need to
skip the TSC sync checks.

Along with this also set the CONSTANT_TSC bit when on VMware, since we
still want to use TSC as clocksource on VM running over hardware which
has unsynchronized TSC's (opteron's), since the hypervisor will take
care of providing consistent TSC to the guest.
Signed-off-by: NAlok N Kataria <akataria@vmware.com>
Signed-off-by: NDan Hecht <dhecht@vmware.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Use WARN() instead of a printk+WARN_ON() pair; this way the message
becomes part of the warning section for better reporting/collection.
This also allowed the folding of some if()'s into the WARN()
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Cc: akpm@linux-foundation.org
Signed-off-by: NIngo Molnar <mingo@elte.hu>

add warning to check_tsc_warp() - if get_cycles() does not progress.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

100 million max # of loops is a bit too much - reduce it to 10 million.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

rdtsc is now speculation-safe, so no need for the sync variants of
the APIs.

[ mingo@elte.hu: removed the nsec_barrier() complication. ]
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

s2ram recently became useful here, except for the kernel's annoying
habit of disabling my P4's perfectly good TSC.

[  107.894470] CPU 1 is now offline
[  107.894474] SMP alternatives: switching to UP code
[  107.895832] CPU0 attaching sched-domain:
[  107.895836]  domain 0: span 1
[  107.895838]   groups: 1
[  107.896097] CPU1 is down
[    3.726156] Intel machine check architecture supported.
[    3.726165] Intel machine check reporting enabled on CPU#0.
[    3.726167] CPU0: Intel P4/Xeon Extended MCE MSRs (12) available
[    3.726170] CPU0: Thermal monitoring enabled
[    3.726175] Back to C!
[    3.726708] Force enabled HPET at resume
[    3.726775] Enabling non-boot CPUs ...
[    3.727049] CPU0 attaching NULL sched-domain.
[    3.727165] SMP alternatives: switching to SMP code
[    3.727858] Booting processor 1/1 eip 3000
[    3.727862] CPU 1 irqstacks, hard=b042f000 soft=b042d000
[    3.738173] Initializing CPU#1
[    3.798912] Calibrating delay using timer specific routine.. 5986.12 BogoMIPS (lpj=2993061)
[    3.798920] CPU: After generic identify, caps: bfebfbff 00000000 00000000 00000000 00004400 00000000 00000000 00000000
[    3.798931] CPU: Trace cache: 12K uops, L1 D cache: 8K
[    3.798934] CPU: L2 cache: 512K
[    3.798936] CPU: Physical Processor ID: 0
[    3.798938] CPU: After all inits, caps: bfebfbff 00000000 00000000 0000b080 00004400 00000000 00000000 00000000
[    3.798946] Intel machine check architecture supported.
[    3.798952] Intel machine check reporting enabled on CPU#1.
[    3.798955] CPU1: Intel P4/Xeon Extended MCE MSRs (12) available
[    3.798959] CPU1: Thermal monitoring enabled
[    3.799161] CPU1: Intel(R) Pentium(R) 4 CPU 3.00GHz stepping 09
[    3.799187] checking TSC synchronization [CPU#0 -> CPU#1]:
[    3.819181] Measured 63588552840 cycles TSC warp between CPUs, turning off TSC clock.
[    3.819184] Marking TSC unstable due to: check_tsc_sync_source failed.

If check_tsc_warp() is called after initial boot, and the TSC has in the
meantime been set (BIOS, user, silicon, elves) to a value lower than the
last stored/stale value, we blame the TSC.  Reset to pristine condition
after every test.
Signed-off-by: NMike Galbraith <efault@gmx.de>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>