[GIT PULL] ring-buffer: Updates for v7.1

[Steven Rostedt <rostedt@goodmis.org>]

Linus,

ring-buffer updates for 7.1:

- Add remote buffers for pKVM

  pKVM has a hypervisor component that is used to protect the guest from the
  host kernel. This hypervisor is a black box to the kernel as the kernel is
  to user space. The remote buffers are used to have a memory mapping
  between the hypervisor and the kernel where kernel may send commands to
  enable tracing within the hypervisor. Then the kernel will read this
  memory mapping just like user space can read the memory mapped ring buffer
  of the kernel tracing system.

  Since the hypervisor only has a single context, it doesn't need to worry
  about races between normal context, interrupt context and NMIs like the
  kernel does. The ring buffer it uses doesn't need to be as complex. The
  remote buffers are a simple version of the ring buffer that works in a
  single context. They are still per-CPU and use sub buffers. The data
  layout is the same as the kernel's ring buffer to share the same parsing.

  Currently, only ARM64 implements pKVM, but there's work to implement it
  also in x86. The remote buffer code is separated out from the ARM
  implementation so that it can be used in the future by x86.

  The ARM64 updates for pKVM is in the ARM/KVM tree and it merged in the
  remote buffers of this tree.

- Merge commit f35dbac69421 ("ring-buffer: Fix to update per-subbuf entries of persistent ring buffer")`

  A fix was merged upstream that some new changes depended on. The upstream
  commit was merged into the ring buffer branch to fulfil the dependency.

- Make the backup instance non reusable

  The backup instance is a copy of the persistent ring buffer so that the
  persistent ring buffer could start recording again without using the data
  from the previous boot. The backup isn't for normal tracing. It is made
  read-only, and after it is consumed, it is automatically removed.

- Have backup copy persistent instance before it starts recording

  To allow the persistent ring buffer to start recording from the kernel
  command line commands, move the copy of the backup instance to before the
  the command line options start recording.

- Report header_page overwrite field as "char" and not "int'

  The rust parser of the header_page file was triggering a warning when it
  defined the overwrite variable as "int" but it was only a single byte in
  size.

- Fix memory barriers for the trace_buffer CPU mask

  When a CPU comes online, the bit is set to allow readers to know that the
  CPU buffer is allocated. The bit is set after the allocation is done, and
  a smp_wmb() is performed after the allocation and before the setting of
  the bit. But instead of adding a smp_rmb() to all readers, since once a
  buffer is created for a CPU it is not deleted if that CPU goes offline, so
  this allocation is almost always done at boot up before any readers exist.

  If for the unlikely case where a CPU comes online for the first time after
  the system boot has finished, send an IPI to all CPUs to force the
  smp_rmb() for each CPU.

- Show clock function being used in debugging ring buffer data

  When the ring buffer checks are enabled and the ring buffer detects an
  inconsistency in the times of the invents, print out the clock being used
  when the error occurred. There was a very hard to hit bug that would
  happen every so often and it ended up being only triggered when the jiffies
  clock was being used. If the bug showed the clock being used, it would
  have been much easier to find the problem (which was an internal function
  was being traced which caused the clock accounting to go off).


Please pull the latest trace-ringbuffer-v7.1 tree, which can be found at:


  git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git
trace-ringbuffer-v7.1

Tag SHA1: 908796a5b4d184750601b6cb227604427fa8fb80
Head SHA1: 6170922f137231b98fc568571befef63e1edff3f


Cao Ruichuang (1):
      ring-buffer: Report header_page overwrite as char

Masami Hiramatsu (Google) (3):
      tracing: Make the backup instance non-reusable
      tracing: Remove the backup instance automatically after read
      tracing/Documentation: Add a section about backup instance

Steven Rostedt (3):
      Merge commit 'f35dbac6942171dc4ce9398d1d216a59224590a9' into trace/ring-buffer/core
      ring-buffer: Show what clock function is used on timestamp errors
      tracing: Allow backup to save persistent ring buffer before it starts

Vincent Donnefort (20):
      ring-buffer: Add page statistics to the meta-page
      ring-buffer: Store bpage pointers into subbuf_ids
      ring-buffer: Introduce ring-buffer remotes
      ring-buffer: Add non-consuming read for ring-buffer remotes
      tracing: Introduce trace remotes
      tracing: Add reset to trace remotes
      tracing: Add non-consuming read to trace remotes
      tracing: Add init callback to trace remotes
      tracing: Add events to trace remotes
      tracing: Add events/ root files to trace remotes
      tracing: Add helpers to create trace remote events
      ring-buffer: Export buffer_data_page and macros
      tracing: Introduce simple_ring_buffer
      tracing: Add a trace remote module for testing
      tracing: selftests: Add trace remote tests
      Documentation: tracing: Add tracing remotes
      tracing: load/unload page callbacks for simple_ring_buffer
      tracing: Check for undefined symbols in simple_ring_buffer
      ring-buffer: Enforce read ordering of trace_buffer cpumask and buffers
      ring-buffer: Prevent off-by-one array access in ring_buffer_desc_page()

----
 Documentation/trace/debugging.rst                  |   19 +
 Documentation/trace/index.rst                      |   11 +
 Documentation/trace/remotes.rst                    |   66 +
 fs/tracefs/inode.c                                 |    1 +
 include/linux/ring_buffer.h                        |   58 +
 include/linux/ring_buffer_types.h                  |   41 +
 include/linux/simple_ring_buffer.h                 |   65 +
 include/linux/trace_remote.h                       |   48 +
 include/linux/trace_remote_event.h                 |   33 +
 include/trace/define_remote_events.h               |   73 ++
 include/uapi/linux/trace_mmap.h                    |    8 +-
 kernel/trace/Kconfig                               |   14 +
 kernel/trace/Makefile                              |   20 +
 kernel/trace/remote_test.c                         |  261 ++++
 kernel/trace/remote_test_events.h                  |   10 +
 kernel/trace/ring_buffer.c                         |  387 +++++-
 kernel/trace/simple_ring_buffer.c                  |  517 ++++++++
 kernel/trace/trace.c                               |  186 ++-
 kernel/trace/trace.h                               |   25 +-
 kernel/trace/trace_boot.c                          |    5 +-
 kernel/trace/trace_events.c                        |   76 +-
 kernel/trace/trace_remote.c                        | 1368 ++++++++++++++++++++
 .../selftests/ftrace/test.d/remotes/buffer_size.tc |   25 +
 .../selftests/ftrace/test.d/remotes/functions      |   88 ++
 .../selftests/ftrace/test.d/remotes/reset.tc       |   90 ++
 .../selftests/ftrace/test.d/remotes/trace.tc       |  127 ++
 .../selftests/ftrace/test.d/remotes/trace_pipe.tc  |  127 ++
 .../selftests/ftrace/test.d/remotes/unloading.tc   |   41 +
 28 files changed, 3654 insertions(+), 136 deletions(-)
 create mode 100644 Documentation/trace/remotes.rst
 create mode 100644 include/linux/ring_buffer_types.h
 create mode 100644 include/linux/simple_ring_buffer.h
 create mode 100644 include/linux/trace_remote.h
 create mode 100644 include/linux/trace_remote_event.h
 create mode 100644 include/trace/define_remote_events.h
 create mode 100644 kernel/trace/remote_test.c
 create mode 100644 kernel/trace/remote_test_events.h
 create mode 100644 kernel/trace/simple_ring_buffer.c
 create mode 100644 kernel/trace/trace_remote.c
 create mode 100644 tools/testing/selftests/ftrace/test.d/remotes/buffer_size.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/remotes/functions
 create mode 100644 tools/testing/selftests/ftrace/test.d/remotes/reset.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/remotes/trace.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/remotes/trace_pipe.tc
 create mode 100644 tools/testing/selftests/ftrace/test.d/remotes/unloading.tc
---------------------------