__kernel_read has a bunch of additional sanity checks, and this moves
the set_fs out of non-core code.
Signed-off-by: Christoph Hellwig <hch@lst.de>

This is the counterpart to __kernel_write, and skip the rw_verify_area
call compared to kernel_read.
Signed-off-by: Christoph Hellwig <hch@lst.de>

Fold it into the two callers.
Signed-off-by: Christoph Hellwig <hch@lst.de>

Consolidate the two in-kernel write helpers to make upcoming changes
easier.  The only difference are the missing call to rw_verify_area
in kernel_write, and an access_ok check that doesn't make sense for
kernel buffers to start with.
Signed-off-by: Christoph Hellwig <hch@lst.de>

Add a WARN_ON_ONCE if the file isn't actually open for write.  This
matches the check done in vfs_write, but actually warn warns as a
kernel user calling write on a file not opened for writing is a pretty
obvious programming error.
Signed-off-by: Christoph Hellwig <hch@lst.de>

This is a very special interface that skips sb_writes protection, and not
used by modules anymore.
Signed-off-by: Christoph Hellwig <hch@lst.de>

While pipes don't really need sb_writers projection, __kernel_write is an
interface better kept private, and the additional rw_verify_area does not
hurt here.
Signed-off-by: Christoph Hellwig <hch@lst.de>

While pipes don't really need sb_writers projection, __kernel_write is an
interface better kept private, and the additional rw_verify_area does not
hurt here.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Ian Kent <raven@themaw.net>

__kernel_write doesn't take a sb_writers references, which we need here.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Howells <dhowells@redhat.com>

Pull perf tooling fixes from Arnaldo Carvalho de Melo:

 - Intel PT fixes for PEBS-via-PT with registers

 - Fixes for Intel PT python based GUI

 - Avoid duplicated sideband events with Intel PT in system wide tracing

 - Remove needless 'dummy' event from TUI menu, used when synthesizing
   meta data events for pre-existing processes

 - Fix corner case segfault when pressing enter in a screen without
   entries in the TUI for report/top

 - Fixes for time stamp handling in libtraceevent

 - Explicitly set utf-8 encoding in perf flamegraph

 - Update arch/x86/lib/memcpy_64.S copy used in 'perf bench mem memcpy',
   silencing perf build warning

* tag 'perf-tools-fixes-2020-07-07' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux:
  perf report TUI: Remove needless 'dummy' event from menu
  perf intel-pt: Fix PEBS sample for XMM registers
  perf intel-pt: Fix displaying PEBS-via-PT with registers
  perf intel-pt: Fix recording PEBS-via-PT with registers
  perf report TUI: Fix segmentation fault in perf_evsel__hists_browse()
  tools lib traceevent: Add proper KBUFFER_TYPE_TIME_STAMP handling
  tools lib traceevent: Add API to read time information from kbuffer
  perf scripts python: exported-sql-viewer.py: Fix time chart call tree
  perf scripts python: exported-sql-viewer.py: Fix zero id in call tree 'Find' result
  perf scripts python: exported-sql-viewer.py: Fix zero id in call graph 'Find' result
  perf scripts python: exported-sql-viewer.py: Fix unexpanded 'Find' result
  perf record: Fix duplicated sideband events with Intel PT system wide tracing
  perf scripts python: export-to-postgresql.py: Fix struct.pack() int argument
  tools arch: Update arch/x86/lib/memcpy_64.S copy used in 'perf bench mem memcpy'
  perf flamegraph: Explicitly set utf-8 encoding

Pull MTD fixes from Miquel Raynal:
 "MTD:
   - Set a missing master partition panic write flag

  Raw NAND:
   - Fix build issue in the xway driver
   - Fix a wrong return code"

* tag 'mtd/fixes-for-5.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/mtd/linux:
  mtd: rawnand: xway: Fix build issue
  mtd: set master partition panic write flag
  nandsim: Fix return code testing of ns_find_operation()

Pull btrfs fixes from David Sterba:

 - regression fix of a leak in global block reserve accounting

 - fix a (hard to hit) race of readahead vs releasepage that could lead
   to crash

 - convert all remaining uses of comment fall through annotations to the
   pseudo keyword

 - fix crash when mounting a fuzzed image with -o recovery

* tag 'for-5.8-rc4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: reset tree root pointer after error in init_tree_roots
  btrfs: fix reclaim_size counter leak after stealing from global reserve
  btrfs: fix fatal extent_buffer readahead vs releasepage race
  btrfs: convert comments to fallthrough annotations

Pull ARC fixes from Vineet Gupta:

 - User build systems to pass -mcpu

 - Fix potential EFA clobber in syscall handler

 - Fix ARCompact 2 levels of interrupts build

 - Detect newer HS CPU releases

 - misc other fixes

* tag 'arc-5.8-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARCv2: support loop buffer (LPB) disabling
  ARC: build: remove deprecated toggle for arc700 builds
  ARC: build: allow users to specify -mcpu
  ARCv2: boot log: detect newer/upconing HS3x/HS4x releases
  ARC: elf: use right ELF_ARCH
  ARC: [arcompact] fix bitrot with 2 levels of interrupt
  ARC: entry: fix potential EFA clobber when TIF_SYSCALL_TRACE

Pull tpm fix from Jarkko Sakkinen:
 "Revert commit e918e570 ("tpm_tis: Remove the HID IFX0102").

  Removing IFX0102 from tpm_tis was not a right move because both
  tpm_tis and tpm_infineon use the same device ID.

  A real fix requires quirks added to both drivers. It can probably wait
  until v5.9 as the bug has existed since 2006"

* tag 'tpmdd-next-v5.8-rc5' of git://git.infradead.org/users/jjs/linux-tpmdd:
  Revert commit e918e570 ("tpm_tis: Remove the HID IFX0102")

This MIPS driver does not support COMPILE_TEST yet and failed to build
under my radar.

Replace 'mtd' chich is not defined in the scope of xway_nand_remove()
by nand_to_mtd(chip). The mistake has been added in the long series
dropping nand_release().

Tested with a 7.3.0 MIPS GCC toolchain built with Buildroot.

Fixes: 9fdd78f7 ("mtd: rawnand: xway: Stop using nand_release()")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200626065511.16424-1-miquel.raynal@bootlin.com

Removing IFX0102 from tpm_tis was not a right move because both tpm_tis
and tpm_infineon use the same device ID. Revert the commit and add a
remark about a bug caused by commit 93e1b7d4 ("[PATCH] tpm: add HID
module parameter").

Fixes: e918e570 ("tpm_tis: Remove the HID IFX0102")
Reported-by: Peter Huewe <peterhuewe@gmx.de>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

Pull kvm fixes from Paolo Bonzini:
 "Bugfixes and a one-liner patch to silence a sparse warning"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  KVM: arm64: Stop clobbering x0 for HVC_SOFT_RESTART
  KVM: arm64: PMU: Fix per-CPU access in preemptible context
  KVM: VMX: Use KVM_POSSIBLE_CR*_GUEST_BITS to initialize guest/host masks
  KVM: x86: Mark CR4.TSD as being possibly owned by the guest
  KVM: x86: Inject #GP if guest attempts to toggle CR4.LA57 in 64-bit mode
  kvm: use more precise cast and do not drop __user
  KVM: x86: bit 8 of non-leaf PDPEs is not reserved
  KVM: X86: Fix async pf caused null-ptr-deref
  KVM: arm64: vgic-v4: Plug race between non-residency and v4.1 doorbell
  KVM: arm64: pvtime: Ensure task delay accounting is enabled
  KVM: arm64: Fix kvm_reset_vcpu() return code being incorrect with SVE
  KVM: arm64: Annotate hyp NMI-related functions as __always_inline
  KVM: s390: reduce number of IO pins to 1

Pull s390 fixes from Heiko Carstens:

 - Initialize jump labels before early command line parsing in order to
   make init_on_alloc and init_on_free options work

 - Fix vfio-ccw build error due to missing include

 - Prevent callchain data collection with hardware sampling, since the
   callchains simply do not exist

 - Prevent multiple registrations of the same zPCI function

 - Update defconfigs

* tag 's390-5.8-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux:
  vfio-ccw: Fix a build error due to missing include of linux/slab.h
  s390: update defconfigs
  s390/cpum_sf: prohibit callchain data collection
  s390/setup: init jump labels before command line parsing
  s390/maccess: add no DAT mode to kernel_write
  s390/pci: fix enabling a reserved PCI function

Merge tag 'kvmarm-fixes-5.8-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-master

KVM/arm fixes for 5.8, take #3

- Disable preemption on context-switching PMU EL0 state happening
  on system register trap
- Don't clobber X0 when tearing down KVM via a soft reset (kexec)

Fixing the common case of:

  perf record
  perf report

And getting just the cycles events.

We now have a 'dummy' event to get perf metadata events that take place
while we synthesize metadata records for pre-existing processes by
traversing procfs, so we always have this extra 'dummy' evsel, but we
don't have to offer it as there will be no samples on it, remove this
distraction.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/lkml/20200706115452.GA2772@redhat.com/Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

The condition to add XMM registers was missing, the regs array needed to
be in the outer scope, and the size of the regs array was too small.

Fixes: 143d34a6 ("perf intel-pt: Add XMM registers to synthesized PEBS sample")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Luwei Kang <luwei.kang@intel.com>
Link: http://lore.kernel.org/lkml/20200630133935.11150-4-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

After recording PEBS-via-PT, perf script will not accept 'iregs' field e.g.

 # perf record -c 10000 -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -I -- ls -l
 ...
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.062 MB perf.data ]
 # ./perf script --itrace=eop -F+iregs
 Samples for 'dummy:u' event do not have IREGS attribute set. Cannot print 'iregs' field.

Fix by using allow_user_set, which is true when recording AUX area data.

Fixes: 9e64cefe ("perf intel-pt: Process options for PEBS event synthesis")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Luwei Kang <luwei.kang@intel.com>
Link: http://lore.kernel.org/lkml/20200630133935.11150-3-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

When recording PEBS-via-PT, the kernel will not accept the intel_pt
event with register sampling e.g.

 # perf record --kcore -c 10000 -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -I -- ls -l
 Error:
 intel_pt/branch=0/: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'

Fix by suppressing register sampling on the intel_pt evsel.

Committer notes:

Adrian informed that this is only available from Tremont onwards, so on
older processors the error continues the same as before.

Fixes: 9e64cefe ("perf intel-pt: Process options for PEBS event synthesis")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Luwei Kang <luwei.kang@intel.com>
Link: http://lore.kernel.org/lkml/20200630133935.11150-2-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

The segmentation fault can be reproduced as following steps:

1) Executing perf report in tui.

2) Typing '/xxxxx' to filter the symbol to get nothing matched.

3) Pressing enter with no entry selected.

Then it will report a segmentation fault.

It is caused by the lack of check of browser->he_selection when
accessing it's member res_samples in perf_evsel__hists_browse().

These processes are meaningful for specified samples, so we can skip
these when nothing is selected.

Fixes: 4968ac8f ("perf report: Implement browsing of individual samples")
Signed-off-by: Wei Li <liwei391@huawei.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Hanjun Guo <guohanjun@huawei.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: http://lore.kernel.org/lkml/20200612094322.39565-1-liwei391@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

HVC_SOFT_RESTART is given values for x0-2 that it should installed
before exiting to the new address so should not set x0 to stub HVC
success or failure code.

Fixes: af42f204 ("arm64: hyp-stub: Zero x0 on successful stub handling")
Cc: stable@vger.kernel.org
Signed-off-by: Andrew Scull <ascull@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200706095259.1338221-1-ascull@google.com

Commit 07da1ffa ("KVM: arm64: Remove host_cpu_context
member from vcpu structure") has, by removing the host CPU
context pointer, exposed that kvm_vcpu_pmu_restore_guest
is called in preemptible contexts:

[  266.932442] BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-aar/779
[  266.939721] caller is debug_smp_processor_id+0x20/0x30
[  266.944157] CPU: 2 PID: 779 Comm: qemu-system-aar Tainted: G            E     5.8.0-rc3-00015-g8d4aa58b2fe3 #1374
[  266.954268] Hardware name: amlogic w400/w400, BIOS 2020.04 05/22/2020
[  266.960640] Call trace:
[  266.963064]  dump_backtrace+0x0/0x1e0
[  266.966679]  show_stack+0x20/0x30
[  266.969959]  dump_stack+0xe4/0x154
[  266.973338]  check_preemption_disabled+0xf8/0x108
[  266.977978]  debug_smp_processor_id+0x20/0x30
[  266.982307]  kvm_vcpu_pmu_restore_guest+0x2c/0x68
[  266.986949]  access_pmcr+0xf8/0x128
[  266.990399]  perform_access+0x8c/0x250
[  266.994108]  kvm_handle_sys_reg+0x10c/0x2f8
[  266.998247]  handle_exit+0x78/0x200
[  267.001697]  kvm_arch_vcpu_ioctl_run+0x2ac/0xab8

Note that the bug was always there, it is only the switch to
using percpu accessors that made it obvious.
The fix is to wrap these accesses in a preempt-disabled section,
so that we sample a coherent context on trap from the guest.

Fixes: 435e53fb ("arm64: KVM: Enable VHE support for :G/:H perf event modifiers")
Cc:: Andrew Murray <amurray@thegoodpenguin.co.uk>
Signed-off-by: Marc Zyngier <maz@kernel.org>

Using a mutex for "print this warning only once" is so overdesigned as
to be actively offensive to my sensitive stomach.

Just use "pr_info_once()" that already does this, although in a
(harmlessly) racy manner that can in theory cause the message to be
printed twice if more than one CPU races on that "is this the first
time" test.

[ If somebody really cares about that harmless data race (which sounds
  very unlikely indeed), that person can trivially fix printk_once() by
  using a simple atomic access, preferably with an optimistic non-atomic
  test first before even bothering to treat the pointless "make sure it
  is _really_ just once" case.

  A mutex is most definitely never the right primitive to use for
  something like this. ]

Yes, this is a small and meaningless detail in a code path that hardly
matters.  But let's keep some code quality standards here, and not
accept outrageously bad code.

Link: https://lore.kernel.org/lkml/CAHk-=wgV9toS7GU3KmNpj8hCS9SeF+A0voHS8F275_mgLhL4Lw@mail.gmail.com/
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull x86 fixes from Thomas Gleixner:
 "A series of fixes for x86:

   - Reset MXCSR in kernel_fpu_begin() to prevent using a stale user
     space value.

   - Prevent writing MSR_TEST_CTRL on CPUs which are not explicitly
     whitelisted for split lock detection. Some CPUs which do not
     support it crash even when the MSR is written to 0 which is the
     default value.

   - Fix the XEN PV fallout of the entry code rework

   - Fix the 32bit fallout of the entry code rework

   - Add more selftests to ensure that these entry problems don't come
     back.

   - Disable 16 bit segments on XEN PV. It's not supported because XEN
     PV does not implement ESPFIX64"

* tag 'x86-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/ldt: Disable 16-bit segments on Xen PV
  x86/entry/32: Fix #MC and #DB wiring on x86_32
  x86/entry/xen: Route #DB correctly on Xen PV
  x86/entry, selftests: Further improve user entry sanity checks
  x86/entry/compat: Clear RAX high bits on Xen PV SYSENTER
  selftests/x86: Consolidate and fix get/set_eflags() helpers
  selftests/x86/syscall_nt: Clear weird flags after each test
  selftests/x86/syscall_nt: Add more flag combinations
  x86/entry/64/compat: Fix Xen PV SYSENTER frame setup
  x86/entry: Move SYSENTER's regs->sp and regs->flags fixups into C
  x86/entry: Assert that syscalls are on the right stack
  x86/split_lock: Don't write MSR_TEST_CTRL on CPUs that aren't whitelisted
  x86/fpu: Reset MXCSR to default in kernel_fpu_begin()

Pull irq fixes from Thomas Gleixner:
 "A set of interrupt chip driver fixes:

   - Ensure the atomicity of affinity updates in the GIC driver

   - Don't try to sleep in atomic context when waiting for the GICv4.1
     to respond. Use polling instead.

   - Typo fixes in Kconfig and warnings"

* tag 'irq-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/gic: Atomically update affinity
  irqchip/riscv-intc: Fix a typo in a pr_warn()
  irqchip/gic-v4.1: Use readx_poll_timeout_atomic() to fix sleep in atomic
  irqchip/loongson-pci-msi: Fix a typo in Kconfig

Pull rcu fixlet from Thomas Gleixner:
 "A single fix for a printk format warning in RCU"

* tag 'core-urgent-2020-07-05' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  rcuperf: Fix printk format warning

Merge tag 'kbuild-fixes-v5.8-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes frin Masahiro Yamada:

 - fix various bugs in xconfig

 - fix some issues in cross-compilation using Clang

 - fix documentation

* tag 'kbuild-fixes-v5.8-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  .gitignore: Do not track `defconfig` from `make savedefconfig`
  kbuild: make Clang build userprogs for target architecture
  kbuild: fix CONFIG_CC_CAN_LINK(_STATIC) for cross-compilation with Clang
  kconfig: qconf: parse newer types at debug info
  kconfig: qconf: navigate menus on hyperlinks
  kconfig: qconf: don't show goback button on splitMode
  kconfig: qconf: simplify the goBack() logic
  kconfig: qconf: re-implement setSelected()
  kconfig: qconf: make debug links work again
  kconfig: qconf: make search fully work again on split mode
  kconfig: qconf: cleanup includes
  docs: kbuild: fix ReST formatting
  gcc-plugins: fix gcc-plugins directory path in documentation

Pull SCSI fixes from James Bottomley:
 "Four small fixes in three drivers.

  The mptfusion one has actually caused user visible issues in certain
  kernel configurations"

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  scsi: mptfusion: Don't use GFP_ATOMIC for larger DMA allocations
  scsi: libfc: Skip additional kref updating work event
  scsi: libfc: Handling of extra kref
  scsi: qla2xxx: Fix a condition in qla2x00_find_all_fabric_devs()

Pull block fixes from Jens Axboe:

 - NVMe fixes from Christoph:
    - Fix crash in multi-path disk add (Christoph)
    - Fix ignore of identify error (Sagi)

 - Fix a compiler complaint that a function should be static (Wei)

* tag 'block-5.8-2020-07-05' of git://git.kernel.dk/linux-block:
  block: make function __bio_integrity_free() static
  nvme: fix a crash in nvme_mpath_add_disk
  nvme: fix identify error status silent ignore

Pull io_uring fix from Jens Axboe:
 "Andres reported a regression with the fix that was merged earlier this
  week, where his setup of using signals to interrupt io_uring CQ waits
  no longer worked correctly.

  Fix this, and also limit our use of TWA_SIGNAL to the case where we
  need it, and continue using TWA_RESUME for task_work as before.

  Since the original is marked for 5.7 stable, let's flush this one out
  early"

* tag 'io_uring-5.8-2020-07-05' of git://git.kernel.dk/linux-block:
  io_uring: fix regression with always ignoring signals in io_cqring_wait()

Pull i2c fixes from Wolfram Sang:
 "The usual driver fixes and documentation updates"

* 'i2c/for-current' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: mlxcpld: check correct size of maximum RECV_LEN packet
  i2c: add Kconfig help text for slave mode
  i2c: slave-eeprom: update documentation
  i2c: eg20t: Load module automatically if ID matches
  i2c: designware: platdrv: Set class based on DMI
  i2c: algo-pca: Add 0x78 as SCL stuck low status for PCA9665

Pull MIPS fixes from Thomas Bogendoerfer:

 - fix for missing hazard barrier

 - DT fix for ingenic

 - DT fix of GPHY names for lantiq

 - fix usage of smp_processor_id() while preemption is enabled

* tag 'mips_fixes_5.8_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux:
  MIPS: Do not use smp_processor_id() in preemptible code
  MIPS: Add missing EHB in mtc0 -> mfc0 sequence for DSPen
  MIPS: ingenic: gcw0: Fix HP detection GPIO.
  MIPS: lantiq: xway: sysctrl: fix the GPHY clock alias names

Use preempt_disable() to fix the following bug under CONFIG_DEBUG_PREEMPT.

[   21.915305] BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-mip/1056
[   21.923996] caller is do_ri+0x1d4/0x690
[   21.927921] CPU: 0 PID: 1056 Comm: qemu-system-mip Not tainted 5.8.0-rc2 #3
[   21.934913] Stack : 0000000000000001 ffffffff81370000 ffffffff8071cd60 a80f926d5ac95694
[   21.942984]         a80f926d5ac95694 0000000000000000 98000007f0043c88 ffffffff80f2fe40
[   21.951054]         0000000000000000 0000000000000000 0000000000000001 0000000000000000
[   21.959123]         ffffffff802d60cc 98000007f0043dd8 ffffffff81f4b1e8 ffffffff81f60000
[   21.967192]         ffffffff81f60000 ffffffff80fe0000 ffff000000000000 0000000000000000
[   21.975261]         fffffffff500cce1 0000000000000001 0000000000000002 0000000000000000
[   21.983331]         ffffffff80fe1a40 0000000000000006 ffffffff8077f940 0000000000000000
[   21.991401]         ffffffff81460000 98000007f0040000 98000007f0043c80 000000fffba8cf20
[   21.999471]         ffffffff8071cd60 0000000000000000 0000000000000000 0000000000000000
[   22.007541]         0000000000000000 0000000000000000 ffffffff80212ab4 a80f926d5ac95694
[   22.015610]         ...
[   22.018086] Call Trace:
[   22.020562] [<ffffffff80212ab4>] show_stack+0xa4/0x138
[   22.025732] [<ffffffff8071cd60>] dump_stack+0xf0/0x150
[   22.030903] [<ffffffff80c73f5c>] check_preemption_disabled+0xf4/0x100
[   22.037375] [<ffffffff80213b84>] do_ri+0x1d4/0x690
[   22.042198] [<ffffffff8020b828>] handle_ri_int+0x44/0x5c
[   24.359386] BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-mip/1072
[   24.368204] caller is do_ri+0x1a8/0x690
[   24.372169] CPU: 4 PID: 1072 Comm: qemu-system-mip Not tainted 5.8.0-rc2 #3
[   24.379170] Stack : 0000000000000001 ffffffff81370000 ffffffff8071cd60 a80f926d5ac95694
[   24.387246]         a80f926d5ac95694 0000000000000000 98001007ef06bc88 ffffffff80f2fe40
[   24.395318]         0000000000000000 0000000000000000 0000000000000001 0000000000000000
[   24.403389]         ffffffff802d60cc 98001007ef06bdd8 ffffffff81f4b818 ffffffff81f60000
[   24.411461]         ffffffff81f60000 ffffffff80fe0000 ffff000000000000 0000000000000000
[   24.419533]         fffffffff500cce1 0000000000000001 0000000000000002 0000000000000000
[   24.427603]         ffffffff80fe0000 0000000000000006 ffffffff8077f940 0000000000000020
[   24.435673]         ffffffff81460020 98001007ef068000 98001007ef06bc80 000000fffbbbb370
[   24.443745]         ffffffff8071cd60 0000000000000000 0000000000000000 0000000000000000
[   24.451816]         0000000000000000 0000000000000000 ffffffff80212ab4 a80f926d5ac95694
[   24.459887]         ...
[   24.462367] Call Trace:
[   24.464846] [<ffffffff80212ab4>] show_stack+0xa4/0x138
[   24.470029] [<ffffffff8071cd60>] dump_stack+0xf0/0x150
[   24.475208] [<ffffffff80c73f5c>] check_preemption_disabled+0xf4/0x100
[   24.481682] [<ffffffff80213b58>] do_ri+0x1a8/0x690
[   24.486509] [<ffffffff8020b828>] handle_ri_int+0x44/0x5c
Signed-off-by: Xingxing Su <suxingxing@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

This resolves the hazard between the mtc0 in the change_c0_status() and
the mfc0 in configure_exception_vector(). Without resolving this hazard
configure_exception_vector() could read an old value and would restore
this old value again. This would revert the changes change_c0_status()
did. I checked this by printing out the read_c0_status() at the end of
per_cpu_trap_init() and the ST0_MX is not set without this patch.

The hazard is documented in the MIPS Architecture Reference Manual Vol.
III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev
6.03 table 8.1 which includes:

   Producer | Consumer | Hazard
  ----------|----------|----------------------------
   mtc0     | mfc0     | any coprocessor 0 register

I saw this hazard on an Atheros AR9344 rev 2 SoC with a MIPS 74Kc CPU.
There the change_c0_status() function would activate the DSPen by
setting ST0_MX in the c0_status register. This was reverted and then the
system got a DSP exception when the DSP registers were saved in
save_dsp() in the first process switch. The crash looks like this:

[    0.089999] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.097796] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear)
[    0.107070] Kernel panic - not syncing: Unexpected DSP exception
[    0.113470] Rebooting in 1 seconds..

We saw this problem in OpenWrt only on the MIPS 74Kc based Atheros SoCs,
not on the 24Kc based SoCs. We only saw it with kernel 5.4 not with
kernel 4.19, in addition we had to use GCC 8.4 or 9.X, with GCC 8.3 it
did not happen.

In the kernel I bisected this problem to commit 9012d011 ("compiler:
allow all arches to enable CONFIG_OPTIMIZE_INLINING"), but when this was
reverted it also happened after commit 172dcd93 ("MIPS: Always
allocate exception vector for MIPSr2+").

Commit 0b24cae4 ("MIPS: Add missing EHB in mtc0 -> mfc0 sequence.")
does similar changes to a different file. I am not sure if there are
more places affected by this problem.
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: <stable@vger.kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Running `make savedefconfig` creates by default `defconfig`, which is,
currently, on git’s radar, for example, `git status` lists this file as
untracked.

So, add the file to `.gitignore`, so it’s ignored by git.
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>