linux.git/arch/x86/kernel/cpu/proc.c, branch v5.6

x86/cpu: Print VMX flags in /proc/cpuinfo using VMX_FEATURES_*

2020-01-13T17:36:02+00:00

Add support for generating VMX feature names in capflags.c and use the
resulting x86_vmx_flags to print the VMX flags in /proc/cpuinfo.  Don't
print VMX flags if no bits are set in word 0, which holds Pin Controls.
Pin Control's INTR and NMI exiting are fundamental pillars of VMX, if
they are not supported then the CPU is broken, it does not actually
support VMX, or the kernel wasn't built with support for the target CPU.

Print the features in a dedicated "vmx flags" line to avoid polluting
the common "flags" and to avoid having to prefix all flags with "vmx_",
which results in horrendously long names.

Keep synthetic VMX flags in cpufeatures to preserve /proc/cpuinfo's ABI
for those flags.  This means that "flags" and "vmx flags" will have
duplicate entries for tpr_shadow (virtual_tpr), vnmi, ept, flexpriority,
vpid and ept_ad, but caps the pollution of "flags" at those six VMX
features.  The vendor-specific code that populates the synthetic flags
will be consolidated in a future patch to further minimize the lasting
damage.

Signed-off-by: Sean Christopherson 
Signed-off-by: Borislav Petkov 
Link: https://lkml.kernel.org/r/20191221044513.21680-12-sean.j.christopherson@intel.com

x86: Convert some slow-path static_cpu_has() callers to boot_cpu_has()

2019-04-08T10:13:34+00:00

Using static_cpu_has() is pointless on those paths, convert them to the
boot_cpu_has() variant.

No functional changes.

Reported-by: Nadav Amit 
Signed-off-by: Borislav Petkov 
Reviewed-by: Rik van Riel 
Reviewed-by: Juergen Gross  # for paravirt
Cc: Aubrey Li 
Cc: Dave Hansen 
Cc: Dominik Brodowski 
Cc: "H. Peter Anvin" 
Cc: Ingo Molnar 
Cc: Jann Horn 
Cc: Joerg Roedel 
Cc: "Kirill A. Shutemov" 
Cc: Konrad Rzeszutek Wilk 
Cc: Thomas Lendacky 
Cc: linux-edac@vger.kernel.org
Cc: Masami Hiramatsu 
Cc: Peter Zijlstra 
Cc: "Rafael J. Wysocki" 
Cc: Sebastian Andrzej Siewior 
Cc: Thomas Gleixner 
Cc: Tony Luck 
Cc: virtualization@lists.linux-foundation.org
Cc: x86@kernel.org
Link: https://lkml.kernel.org/r/20190330112022.28888-3-bp@alien8.de

x86/cpu: Change type of x86_cache_size variable to unsigned int

2018-02-15T00:15:53+00:00

Currently, x86_cache_size is of type int, which makes no sense as we
will never have a valid cache size equal or less than 0. So instead of
initializing this variable to -1, it can perfectly be initialized to 0
and use it as an unsigned variable instead.

Suggested-by: Thomas Gleixner 
Signed-off-by: Gustavo A. R. Silva 
Cc: Borislav Petkov 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Addresses-Coverity-ID: 1464429
Link: http://lkml.kernel.org/r/20180213192208.GA26414@embeddedor.com
Signed-off-by: Ingo Molnar

x86/cpu: Rename cpu_data.x86_mask to cpu_data.x86_stepping

2018-02-15T00:15:52+00:00

x86_mask is a confusing name which is hard to associate with the
processor's stepping.

Additionally, correct an indent issue in lib/cpu.c.

Signed-off-by: Jia Zhang 
[ Updated it to more recent kernels. ]
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: bp@alien8.de
Cc: tony.luck@intel.com
Link: http://lkml.kernel.org/r/1514771530-70829-1-git-send-email-qianyue.zj@alibaba-inc.com
Signed-off-by: Ingo Molnar

x86 / CPU: Always show current CPU frequency in /proc/cpuinfo

2017-11-15T18:46:50+00:00

After commit 890da9cf0983 (Revert "x86: do not use cpufreq_quick_get()
for /proc/cpuinfo "cpu MHz"") the "cpu MHz" number in /proc/cpuinfo
on x86 can be either the nominal CPU frequency (which is constant)
or the frequency most recently requested by a scaling governor in
cpufreq, depending on the cpufreq configuration.  That is somewhat
inconsistent and is different from what it was before 4.13, so in
order to restore the previous behavior, make it report the current
CPU frequency like the scaling_cur_freq sysfs file in cpufreq.

To that end, modify the /proc/cpuinfo implementation on x86 to use
aperfmperf_snapshot_khz() to snapshot the APERF and MPERF feedback
registers, if available, and use their values to compute the CPU
frequency to be reported as "cpu MHz".

However, do that carefully enough to avoid accumulating delays that
lead to unacceptable access times for /proc/cpuinfo on systems with
many CPUs.  Run aperfmperf_snapshot_khz() once on all CPUs
asynchronously at the /proc/cpuinfo open time, add a single delay
upfront (if necessary) at that point and simply compute the current
frequency while running show_cpuinfo() for each individual CPU.

Also, to avoid slowing down /proc/cpuinfo accesses too much, reduce
the default delay between consecutive APERF and MPERF reads to 10 ms,
which should be sufficient to get large enough numbers for the
frequency computation in all cases.

Fixes: 890da9cf0983 (Revert "x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"")
Signed-off-by: Rafael J. Wysocki 
Acked-by: Thomas Gleixner 
Tested-by: Thomas Gleixner 
Acked-by: Ingo Molnar

Revert "x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo"

2017-11-10T19:19:11+00:00

This reverts commit 941f5f0f6ef5338814145cf2b813cf1f98873e2f.

Sadly, it turns out that we really can't just do the cross-CPU IPI to
all CPU's to get their proper frequencies, because it's much too
expensive on systems with lots of cores.

So we'll have to revert this for now, and revisit it using a smarter
model (probably doing one system-wide IPI at open time, and doing all
the frequency calculations in parallel).

Reported-by: WANG Chao 
Reported-by: Ingo Molnar 
Cc: Rafael J Wysocki 
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds

x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo

2017-11-03T15:50:13+00:00

Commit 890da9cf0983 (Revert "x86: do not use cpufreq_quick_get() for
/proc/cpuinfo "cpu MHz"") is not sufficient to restore the previous
behavior of "cpu MHz" in /proc/cpuinfo on x86 due to some changes
made after the commit it has reverted.

To address this, make the code in question use arch_freq_get_on_cpu()
which also is used by cpufreq for reporting the current frequency of
CPUs and since that function doesn't really depend on cpufreq in any
way, drop the CONFIG_CPU_FREQ dependency for the object file
containing it.

Also refactor arch_freq_get_on_cpu() somewhat to avoid IPIs and
return cached values right away if it is called very often over a
short time (to prevent user space from triggering IPI storms through
it).

Fixes: 890da9cf0983 (Revert "x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"")
Cc: stable@kernel.org   # 4.13 - together with 890da9cf0983
Signed-off-by: Rafael J. Wysocki 
Signed-off-by: Linus Torvalds

Revert "x86: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz""

2017-11-02T21:06:32+00:00

This reverts commit 51204e0639c49ada02fd823782ad673b6326d748.

There wasn't really any good reason for it, and people are complaining
(rightly) that it broke existing practice.

Cc: Len Brown 
Cc: Thomas Gleixner 
Cc: Rafael J. Wysocki 
Signed-off-by: Linus Torvalds

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: do not use cpufreq_quick_get() for /proc/cpuinfo "cpu MHz"

2017-06-23T23:45:47+00:00

cpufreq_quick_get() allows cpufreq drivers to over-ride cpu_khz
that is otherwise reported in x86 /proc/cpuinfo "cpu MHz".

There are four problems with this scheme,
any of them is sufficient justification to delete it.

 1. Depending on which cpufreq driver is loaded, the behavior
    of this field is different.

 2. Distros complain that they have to explain to users
    why and how this field changes.  Distros have requested a constant.

 3. The two major providers of this information, acpi_cpufreq
    and intel_pstate, both "get it wrong" in different ways.

    acpi_cpufreq lies to the user by telling them that
    they are running at whatever frequency was last
    requested by software.

    intel_pstate lies to the user by telling them that
    they are running at the average frequency computed
    over an undefined measurement.  But an average computed
    over an undefined interval, is itself, undefined...

 4. On modern processors, user space utilities, such as
    turbostat(1), are more accurate and more precise, while
    supporing concurrent measurement over arbitrary intervals.

Users who have been consulting /proc/cpuinfo to
track changing CPU frequency will be dissapointed that
it no longer wiggles -- perhaps being unaware of the
limitations of the information they have been consuming.

Yes, they can change their scripts to look in sysfs
cpufreq/scaling_cur_frequency.  Here they will find the same
data of dubious quality here removed from /proc/cpuinfo.
The value in sysfs will be addressed in a subsequent patch
to address issues 1-3, above.

Issue 4 will remain -- users that really care about
accurate frequency information should not be using either
proc or sysfs kernel interfaces.
They should be using using turbostat(8), or a similar
purpose-built analysis tool.

Signed-off-by: Len Brown 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Rafael J. Wysocki