selftests/powerpc/dscr: Improve DSCR explicit random test case

The tests currently have a single writer thread updating the system
DSCR with a 1/1000 chance looped only 100 times. So only around one in
10 runs actually do anything.

* Add multiple threads to the dscr_explicit_random_test case.
* Use a barrier to make all the threads start work as simultaneously as
possible.
* Use a rwlock and make all threads have a reasonable chance to write to
the DSCR on each iteration.
PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP is used to prevent
writers from starving while all the other threads keep reading.
Logging the reads/writes shows a decent mix across the whole test.
* Allow all threads a chance to write.
* Make the chance of writing more likely.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230406043320.125138-6-bgray@linux.ibm.com

selftests/powerpc: Add {read,write}_{long,ulong}

Add helper functions to read and write (unsigned) long values directly
from/to files. One of the kernel interfaces uses hex strings, so we need
to allow passing a base too.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230203003947.38033-5-bgray@linux.ibm.com

selftests/powerpc: Add generic read/write file util

File read/write is reimplemented in about 5 different ways in the
various PowerPC selftests. This indicates it should be a common util.

Add a common read_file / write_file implementation and convert users
to it where (easily) possible.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230203003947.38033-2-bgray@linux.ibm.com

selftests/powerpc: Use mfspr/mtspr macros

No need to write inline asm for mtspr/mfspr, we have macros for this
in reg.h

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221128041948.58339-2-bgray@linux.ibm.com

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

Based on 2 normalized pattern(s):

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation

this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

locking/atomics, selftests/powerpc: Convert ACCESS_ONCE() to READ_ONCE()/WRITE_ONCE()

For several reasons, it is desirable to use {READ,WRITE}_ONCE() in
preference to ACCESS_ONCE(), and new code is expected to use one of the
former. So far, there's been no reason to change most existing uses of
ACCESS_ONCE(), as these aren't currently harmful.

However, for some features it is necessary to instrument reads and
writes separately, which is not possible with ACCESS_ONCE(). This
distinction is critical to correct operation.

The bulk of the kernel code can be transformed via Coccinelle to use
{READ,WRITE}_ONCE(), though this only modifies users of ACCESS_ONCE(),
and not the implementation itself. As such, it has the potential to
break homebrew ACCESS_ONCE() macros seen in some user code in the kernel
tree (e.g. the virtio code, as fixed in commit ea9156fb3b71d9f7).

To avoid fragility if/when that transformation occurs, and to align with
the preferred usage of {READ,WRITE}_ONCE(), this patch updates the DSCR
selftest code to use READ_ONCE() rather than ACCESS_ONCE(). There should
be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: davem@davemloft.net
Cc: linux-arch@vger.kernel.org
Cc: snitzer@redhat.com
Cc: thor.thayer@linux.intel.com
Cc: tj@kernel.org
Cc: viro@zeniv.linux.org.uk
Cc: will.deacon@arm.com
Link: http://lkml.kernel.org/r/1508792849-3115-11-git-send-email-paulmck@linux.vnet.ibm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

selftests/powerpc: Add more SPR numbers, TM & VMX instructions to 'reg.h'/'instructions.h'

This patch adds SPR number for TAR, PPR, DSCR special
purpose registers. It also adds TM, VSX, VMX related
instructions which will then be used by patches later
in the series.

Now that the new DSCR register definitions (SPRN_DSCR_PRIV and
SPRN_DSCR) are defined outside this directory, use them instead.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Simon Guo <wei.guo.simon@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

selftests/powerpc: Add test for system wide DSCR default

This patch adds a test case for the system wide DSCR default value,
which when changed through it's sysfs interface must be visible to all
threads reading DSCR either through the privilege state SPR or the
problem state SPR. The DSCR value change should be immediate as well.

Acked-by: Shuah Khan <shuahkh@osg.samsung.com>
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>