linux-toradex.git/include/linux/context_tracking.h, branch v5.1-rc1

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

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

2016-08-02T20:11:27+00:00

Pull KVM updates from Paolo Bonzini:

 - ARM: GICv3 ITS emulation and various fixes.  Removal of the
   old VGIC implementation.

 - s390: support for trapping software breakpoints, nested
   virtualization (vSIE), the STHYI opcode, initial extensions
   for CPU model support.

 - MIPS: support for MIPS64 hosts (32-bit guests only) and lots
   of cleanups, preliminary to this and the upcoming support for
   hardware virtualization extensions.

 - x86: support for execute-only mappings in nested EPT; reduced
   vmexit latency for TSC deadline timer (by about 30%) on Intel
   hosts; support for more than 255 vCPUs.

 - PPC: bugfixes.

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (302 commits)
  KVM: PPC: Introduce KVM_CAP_PPC_HTM
  MIPS: Select HAVE_KVM for MIPS64_R{2,6}
  MIPS: KVM: Reset CP0_PageMask during host TLB flush
  MIPS: KVM: Fix ptr->int cast via KVM_GUEST_KSEGX()
  MIPS: KVM: Sign extend MFC0/RDHWR results
  MIPS: KVM: Fix 64-bit big endian dynamic translation
  MIPS: KVM: Fail if ebase doesn't fit in CP0_EBase
  MIPS: KVM: Use 64-bit CP0_EBase when appropriate
  MIPS: KVM: Set CP0_Status.KX on MIPS64
  MIPS: KVM: Make entry code MIPS64 friendly
  MIPS: KVM: Use kmap instead of CKSEG0ADDR()
  MIPS: KVM: Use virt_to_phys() to get commpage PFN
  MIPS: Fix definition of KSEGX() for 64-bit
  KVM: VMX: Add VMCS to CPU's loaded VMCSs before VMPTRLD
  kvm: x86: nVMX: maintain internal copy of current VMCS
  KVM: PPC: Book3S HV: Save/restore TM state in H_CEDE
  KVM: PPC: Book3S HV: Pull out TM state save/restore into separate procedures
  KVM: arm64: vgic-its: Simplify MAPI error handling
  KVM: arm64: vgic-its: Make vgic_its_cmd_handle_mapi similar to other handlers
  KVM: arm64: vgic-its: Turn device_id validation into generic ID validation
  ...

x86/entry: Avoid interrupt flag save and restore

2016-07-10T11:33:02+00:00

Thanks to all the work that was done by Andy Lutomirski and others,
enter_from_user_mode() and prepare_exit_to_usermode() are now called only with
interrupts disabled.  Let's provide them a version of user_enter()/user_exit()
that skips saving and restoring the interrupt flag.

On an AMD-based machine I tested this patch on, with force-enabled
context tracking, the speed-up in system calls was 90 clock cycles or 6%,
measured with the following simple benchmark:

    #include 
    #include 
    #include 
    #include 

    unsigned long rdtsc()
    {
        unsigned long result;
        asm volatile("rdtsc; shl $32, %%rdx; mov %%eax, %%eax\n"
                     "or %%rdx, %%rax" : "=a" (result) : : "rdx");
        return result;
    }

    int main()
    {
        unsigned long tsc1, tsc2;
        int pid = getpid();
        int i;

        tsc1 = rdtsc();
        for (i = 0; i < 100000000; i++)
            kill(pid, SIGWINCH);
        tsc2 = rdtsc();

        printf("%ld\n", tsc2 - tsc1);
    }

Signed-off-by: Paolo Bonzini 
Reviewed-by: Rik van Riel 
Reviewed-by: Andy Lutomirski 
Acked-by: Paolo Bonzini 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: H. Peter Anvin 
Cc: Josh Poimboeuf 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Cc: kvm@vger.kernel.org
Link: http://lkml.kernel.org/r/1466434712-31440-2-git-send-email-pbonzini@redhat.com
Signed-off-by: Ingo Molnar

context_tracking: move rcu_virt_note_context_switch out of kvm_host.h

2016-06-28T12:15:25+00:00

Make kvm_guest_{enter,exit} and __kvm_guest_{enter,exit} trivial wrappers
around the code in context_tracking.h.  Name the context_tracking.h functions
consistently with what those for kernel<->user switch.

Cc: Andy Lutomirski 
Cc: Peter Zijlstra 
Cc: H. Peter Anvin 
Cc: Ingo Molnar 
Cc: Thomas Gleixner 
Reviewed-by: Rik van Riel 
Signed-off-by: Paolo Bonzini

sched/cputime: Rename vtime_accounting_enabled() to vtime_accounting_cpu_enabled()

2015-12-04T09:34:45+00:00

vtime_accounting_enabled() checks if vtime is running on the current CPU
and is as such a misnomer. Lets rename it to a function that reflect its
locality. We are going to need the current name for a function that tells
if vtime runs at all on some CPU.

Signed-off-by: Frederic Weisbecker 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Chris Metcalf 
Cc: Christoph Lameter 
Cc: Hiroshi Shimamoto 
Cc: Linus Torvalds 
Cc: Luiz Capitulino 
Cc: Mike Galbraith 
Cc: Paul E . McKenney 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1447948054-28668-6-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

context_tracking: avoid irq_save/irq_restore on guest entry and exit

2015-11-10T11:06:23+00:00

guest_enter and guest_exit must be called with interrupts disabled,
since they take the vtime_seqlock with write_seq{lock,unlock}.
Therefore, it is not necessary to check for exceptions, nor to
save/restore the IRQ state, when context tracking functions are
called by guest_enter and guest_exit.

Split the body of context_tracking_entry and context_tracking_exit
out to __-prefixed functions, and use them from KVM.

Rik van Riel has measured this to speed up a tight vmentry/vmexit
loop by about 2%.

Cc: Andy Lutomirski 
Cc: Frederic Weisbecker 
Cc: Paul McKenney 
Reviewed-by: Rik van Riel 
Tested-by: Rik van Riel 
Signed-off-by: Paolo Bonzini

context_tracking: remove duplicate enabled check

2015-11-10T11:06:22+00:00

All calls to context_tracking_enter and context_tracking_exit
are already checking context_tracking_is_enabled, except the
context_tracking_user_enter and context_tracking_user_exit
functions left in for the benefit of assembly calls.

Pull the check up to those functions, by making them simple
wrappers around the user_enter and user_exit inline functions.

Cc: Frederic Weisbecker 
Cc: Paul McKenney 
Reviewed-by: Rik van Riel 
Tested-by: Rik van Riel 
Acked-by: Andy Lutomirski 
Signed-off-by: Paolo Bonzini

context_tracking: Add ct_state() and CT_WARN_ON()

2015-07-07T08:59:04+00:00

This will let us sprinkle sanity checks around the kernel
without making too much of a mess.

Signed-off-by: Andy Lutomirski 
Cc: Andy Lutomirski 
Cc: Borislav Petkov 
Cc: Brian Gerst 
Cc: Denys Vlasenko 
Cc: Denys Vlasenko 
Cc: Frederic Weisbecker 
Cc: H. Peter Anvin 
Cc: Kees Cook 
Cc: Linus Torvalds 
Cc: Oleg Nesterov 
Cc: Peter Zijlstra 
Cc: Rik van Riel 
Cc: Thomas Gleixner 
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/5da41fb2ceb29eac671f427c67040401ba2a1fa0.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar

context_tracking: Inherit TIF_NOHZ through forks instead of context switches

2015-05-07T10:02:51+00:00

TIF_NOHZ is used by context_tracking to force syscall slow-path
on every task in order to track userspace roundtrips. As such,
it must be set on all running tasks.

It's currently explicitly inherited through context switches.
There is no need to do it in this fast-path though. The flag
could simply be set once for all on all tasks, whether they are
running or not.

Lets do this by setting the flag for the init task on early boot,
and let it propagate through fork inheritance.

While at it, mark context_tracking_cpu_set() as init code, we
only need it at early boot time.

Suggested-by: Oleg Nesterov 
Signed-off-by: Frederic Weisbecker 
Reviewed-by: Rik van Riel 
Cc: Borislav Petkov 
Cc: Chris Metcalf 
Cc: Dave Jones 
Cc: H. Peter Anvin 
Cc: Martin Schwidefsky 
Cc: Mike Galbraith 
Cc: Paul E . McKenney 
Cc: Paul E. McKenney 
Cc: Peter Zijlstra 
Cc: Rafael J . Wysocki 
Cc: Thomas Gleixner 
Link: http://lkml.kernel.org/r/1430928266-24888-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar

kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest

2015-03-09T14:43:03+00:00

The host kernel is not doing anything while the CPU is executing
a KVM guest VCPU, so it can be marked as being in an extended
quiescent state, identical to that used when running user space
code.

The only exception to that rule is when the host handles an
interrupt, which is already handled by the irq code, which
calls rcu_irq_enter and rcu_irq_exit.

The guest_enter and guest_exit functions already switch vtime
accounting independent of context tracking. Leave those calls
where they are, instead of moving them into the context tracking
code.

Reviewed-by: Paul E. McKenney 
Signed-off-by: Rik van Riel 
Cc: Paul E. McKenney 
Cc: Andy Lutomirski 
Cc: Will deacon 
Cc: Marcelo Tosatti 
Cc: Christian Borntraeger 
Cc: Luiz Capitulino 
Cc: Paolo Bonzini 
Signed-off-by: Frederic Weisbecker