linux-stable.git/arch/x86/kernel/tsc_sync.c, branch v5.2

Merge branch 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-11-14T03:07:38+00:00

Pull x86 timer updates from Thomas Gleixner:
 "These updates are related to TSC handling:

   - Support platforms which have synchronized TSCs but the boot CPU has
     a non zero TSC_ADJUST value, which is considered a firmware bug on
     normal systems.

     This applies to HPE/SGI UV platforms where the platform firmware
     uses TSC_ADJUST to ensure TSC synchronization across a huge number
     of sockets, but due to power on timings the boot CPU cannot be
     guaranteed to have a zero TSC_ADJUST register value.

   - Fix the ordering of udelay calibration and kvmclock_init()

   - Cleanup the udelay and calibration code"

* 'x86-timers-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/tsc: Mark cyc2ns_init() and detect_art() __init
  x86/platform/UV: Mark tsc_check_sync as an init function
  x86/tsc: Make CONFIG_X86_TSC=n build work again
  x86/platform/UV: Add check of TSC state set by UV BIOS
  x86/tsc: Provide a means to disable TSC ART
  x86/tsc: Drastically reduce the number of firmware bug warnings
  x86/tsc: Skip TSC test and error messages if already unstable
  x86/tsc: Add option that TSC on Socket 0 being non-zero is valid
  x86/timers: Move simple_udelay_calibration() past kvmclock_init()
  x86/timers: Make recalibrate_cpu_khz() void
  x86/timers: Move the simple udelay calibration to tsc.h

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

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: Kate Stewart 
Reviewed-by: Philippe Ombredanne 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

x86/tsc: Drastically reduce the number of firmware bug warnings

2017-10-16T20:50:36+00:00

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: Mike Travis 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Dimitri Sivanich 
Reviewed-by: Russ Anderson 
Reviewed-by: Peter Zijlstra 
Cc: Prarit Bhargava 
Cc: Andrew Banman 
Cc: Bin Gao 
Link: https://lkml.kernel.org/r/20171012163202.175062400@stormcage.americas.sgi.com

x86/tsc: Skip TSC test and error messages if already unstable

2017-10-16T20:50:36+00:00

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: Mike Travis 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Dimitri Sivanich 
Reviewed-by: Russ Anderson 
Reviewed-by: Peter Zijlstra 
Cc: Prarit Bhargava 
Cc: Andrew Banman 
Cc: Bin Gao 
Link: https://lkml.kernel.org/r/20171012163202.060777495@stormcage.americas.sgi.com

x86/tsc: Add option that TSC on Socket 0 being non-zero is valid

2017-10-16T20:50:36+00:00

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: Mike Travis 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Dimitri Sivanich 
Reviewed-by: Russ Anderson 
Reviewed-by: Andrew Banman 
Reviewed-by: Peter Zijlstra 
Cc: Prarit Bhargava 
Cc: Andrew Banman 
Cc: Bin Gao 
Link: https://lkml.kernel.org/r/20171012163201.944370012@stormcage.americas.sgi.com

x86/tsc: Remove the TSC_ADJUST clamp

2017-06-04T19:55:53+00:00

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: Peter Zijlstra (Intel) 
Cc: kevin.b.stanton@intel.com
Link: http://lkml.kernel.org/r/20170531155306.100950003@infradead.org
Signed-off-by: Thomas Gleixner

x86/tsc: Make the TSC ADJUST sanitizing work for tsc_reliable

2017-02-10T08:47:17+00:00

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: Thomas Gleixner 
Cc: Peter Zijlstra 
Cc: Olof Johansson 
Link: http://lkml.kernel.org/r/20170209151231.491189912@linutronix.de
Signed-off-by: Thomas Gleixner

x86/tsc: Limit the adjust value further

2016-12-18T15:37:04+00:00

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: Thomas Gleixner 
Cc: Roland Scheidegger 
Cc: Bruce Schlobohm 
Cc: Kevin Stanton 
Cc: Peter Zijlstra 
Cc: Borislav Petkov

x86/tsc: Annotate printouts as firmware bug

2016-12-18T15:35:15+00:00

Make it more obvious that the BIOS is screwed up.

Signed-off-by: Thomas Gleixner 
Cc: Roland Scheidegger 
Cc: Bruce Schlobohm 
Cc: Kevin Stanton 
Cc: Peter Zijlstra 
Cc: Borislav Petkov

x86/tsc: Force TSC_ADJUST register to value >= zero

2016-12-15T10:44:29+00:00

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: Roland Scheidegger 
Signed-off-by: Thomas Gleixner 
Cc: Bruce Schlobohm 
Cc: Kevin Stanton 
Cc: Peter Zijlstra 
Cc: Allen Hung 
Cc: Borislav Petkov 
Link: http://lkml.kernel.org/r/20161213131211.397588033@linutronix.de
Signed-off-by: Thomas Gleixner