Just when I had decided that flush_cache_range() was always called with
a valid context, Helge reported two cases where the
"BUG_ON(!vma->vm_mm->context);" was hit on the phantom buildd:

 kernel BUG at /mnt/sdb6/linux/linux-4.15.4/arch/parisc/kernel/cache.c:587!
 CPU: 1 PID: 3254 Comm: kworker/1:2 Tainted: G D 4.15.0-1-parisc64-smp #1 Debian 4.15.4-1+b1
 Workqueue: events free_ioctx
  IAOQ[0]: flush_cache_range+0x164/0x168
  IAOQ[1]: flush_cache_page+0x0/0x1c8
  RP(r2): unmap_page_range+0xae8/0xb88
 Backtrace:
  [<00000000404a6980>] unmap_page_range+0xae8/0xb88
  [<00000000404a6ae0>] unmap_single_vma+0xc0/0x188
  [<00000000404a6cdc>] zap_page_range_single+0x134/0x1f8
  [<00000000404a702c>] unmap_mapping_range+0x1cc/0x208
  [<0000000040461518>] truncate_pagecache+0x98/0x108
  [<0000000040461624>] truncate_setsize+0x9c/0xb8
  [<00000000405d7f30>] put_aio_ring_file+0x80/0x100
  [<00000000405d803c>] aio_free_ring+0x8c/0x290
  [<00000000405d82c0>] free_ioctx+0x80/0x180
  [<0000000040284e6c>] process_one_work+0x21c/0x668
  [<00000000402854c4>] worker_thread+0x20c/0x778
  [<0000000040291d44>] kthread+0x2d4/0x2e0
  [<0000000040204020>] end_fault_vector+0x20/0xc0

This indicates that we need to handle the no context case in
flush_cache_range() as we do in flush_cache_mm().

In thinking about this, I realized that we don't need to flush the TLB
when there is no context.  So, I added context checks to the large flush
cases in flush_cache_mm() and flush_cache_range().  The large flush case
occurs frequently in flush_cache_mm() and the change should improve fork
performance.

The v2 version of this change removes the BUG_ON from flush_cache_page()
by skipping the TLB flush when there is no context.  I also added code
to flush the TLB in flush_cache_mm() and flush_cache_range() when we
have a context that's not current.  Now all three routines handle TLB
flushes in a similar manner.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.9+
Signed-off-by: Helge Deller <deller@gmx.de>

Pull parisc fixes from Helge Deller:

 - a patch to change the ordering of cache and TLB flushes to hopefully
   fix the random segfaults we very rarely face (by Dave Anglin).

 - a patch to hide the virtual kernel memory layout due to security
   reasons.

 - two small patches to make the kernel run more smoothly under qemu.

* 'parisc-4.16-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: Reduce irq overhead when run in qemu
  parisc: Use cr16 interval timers unconditionally on qemu
  parisc: Check if secondary CPUs want own PDC calls
  parisc: Hide virtual kernel memory layout
  parisc: Fix ordering of cache and TLB flushes

When run under QEMU, calling mfctl(16) creates some overhead because the
qemu timer has to be scaled and moved into the register. This patch
reduces the number of calls to mfctl(16) by moving the calls out of the
loops.

Additionally, increase the minimal time interval to 8000 cycles instead
of 500 to compensate possible QEMU delays when delivering interrupts.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # 4.14+

When running on qemu we know that the (emulated) cr16 cpu-internal
clocks are syncronized. So let's use them unconditionally on qemu.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org # 4.14+

The architecture specification says (for 64-bit systems): PDC is a per
processor resource, and operating system software must be prepared to
manage separate pointers to PDCE_PROC for each processor.  The address
of PDCE_PROC for the monarch processor is stored in the Page Zero
location MEM_PDC. The address of PDCE_PROC for each non-monarch
processor is passed in gr26 when PDCE_RESET invokes OS_RENDEZ.

Currently we still use one PDC for all CPUs, but in case we face a
machine which is following the specification let's warn about it.

Signed-off-by: Helge Deller <deller@gmx.de>

For security reasons do not expose the virtual kernel memory layout to
userspace.

Signed-off-by: Helge Deller <deller@gmx.de>
Suggested-by: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org # 4.15
Reviewed-by: Kees Cook <keescook@chromium.org>

The change to flush_kernel_vmap_range() wasn't sufficient to avoid the
SMP stalls.  The problem is some drivers call these routines with
interrupts disabled.  Interrupts need to be enabled for flush_tlb_all()
and flush_cache_all() to work.  This version adds checks to ensure
interrupts are not disabled before calling routines that need IPI
interrupts.  When interrupts are disabled, we now drop into slower code.

The attached change fixes the ordering of cache and TLB flushes in
several cases.  When we flush the cache using the existing PTE/TLB
entries, we need to flush the TLB after doing the cache flush.  We don't
need to do this when we flush the entire instruction and data caches as
these flushes don't use the existing TLB entries.  The same is true for
tmpalias region flushes.

The flush_kernel_vmap_range() and invalidate_kernel_vmap_range()
routines have been updated.

Secondly, we added a new purge_kernel_dcache_range_asm() routine to
pacache.S and use it in invalidate_kernel_vmap_range().  Nominally,
purges are faster than flushes as the cache lines don't have to be
written back to memory.

Hopefully, this is sufficient to resolve the remaining problems due to
cache speculation.  So far, testing indicates that this is the case.  I
did work up a patch using tmpalias flushes, but there is a performance
hit because we need the physical address for each page, and we also need
to sequence access to the tmpalias flush code.  This increases the
probability of stalls.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Cc: stable@vger.kernel.org # 4.9+
Signed-off-by: Helge Deller <deller@gmx.de>

Pull clk updates from Stephen Boyd:
 "The core framework has a handful of patches this time around, mostly
  due to the clk rate protection support added by Jerome Brunet.

  This feature will allow consumers to lock in a certain rate on the
  output of a clk so that things like audio playback don't hear pops
  when the clk frequency changes due to shared parent clks changing
  rates. Currently the clk API doesn't guarantee the rate of a clk stays
  at the rate you request after clk_set_rate() is called, so this new
  API will allow drivers to express that requirement.

  Beyond this, the core got some debugfs pretty printing patches and a
  couple minor non-critical fixes.

  Looking outside of the core framework diff we have some new driver
  additions and the removal of a legacy TI clk driver. Both of these hit
  high in the dirstat. Also, the removal of the asm-generic/clkdev.h
  file causes small one-liners in all the architecture Kbuild files.

  Overall, the driver diff seems to be the normal stuff that comes all
  the time to fix little problems here and there and to support new
  hardware.

  Summary:

  Core:
   - Clk rate protection
   - Symbolic clk flags in debugfs output
   - Clk registration enabled clks while doing bookkeeping updates

  New Drivers:
   - Spreadtrum SC9860
   - HiSilicon hi3660 stub
   - Qualcomm A53 PLL, SPMI clkdiv, and MSM8916 APCS
   - Amlogic Meson-AXG
   - ASPEED BMC

  Removed Drivers:
   - TI OMAP 3xxx legacy clk (non-DT) support
   - asm*/clkdev.h got removed (not really a driver)

  Updates:
   - Renesas FDP1-0 module clock on R-Car M3-W
   - Renesas LVDS module clock on R-Car V3M
   - Misc fixes to pr_err() prints
   - Qualcomm MSM8916 audio fixes
   - Qualcomm IPQ8074 rounded out support for more peripherals
   - Qualcomm Alpha PLL variants
   - Divider code was using container_of() on bad pointers
   - Allwinner DE2 clks on H3
   - Amlogic minor data fixes and dropping of CLK_IGNORE_UNUSED
   - Mediatek clk driver compile test support
   - AT91 PMC clk suspend/resume restoration support
   - PLL issues fixed on si5351
   - Broadcom IProc PLL calculation updates
   - DVFS support for Armada mvebu CPU clks
   - Allwinner fixed post-divider support
   - TI clkctrl fixes and support for newer SoCs"

* tag 'clk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux: (125 commits)
  clk: aspeed: Handle inverse polarity of USB port 1 clock gate
  clk: aspeed: Fix return value check in aspeed_cc_init()
  clk: aspeed: Add reset controller
  clk: aspeed: Register gated clocks
  clk: aspeed: Add platform driver and register PLLs
  clk: aspeed: Register core clocks
  clk: Add clock driver for ASPEED BMC SoCs
  clk: mediatek: adjust dependency of reset.c to avoid unexpectedly being built
  clk: fix reentrancy of clk_enable() on UP systems
  clk: meson-axg: fix potential NULL dereference in axg_clkc_probe()
  clk: Simplify debugfs registration
  clk: Fix debugfs_create_*() usage
  clk: Show symbolic clock flags in debugfs
  clk: renesas: r8a7796: Add FDP clock
  clk: Move __clk_{get,put}() into private clk.h API
  clk: sunxi: Use CLK_IS_CRITICAL flag for critical clks
  clk: Improve flags doc for of_clk_detect_critical()
  arch: Remove clkdev.h asm-generic from Kbuild
  clk: sunxi-ng: a83t: Add M divider to TCON1 clock
  clk: Prepare to remove asm-generic/clkdev.h
  ...

Pull printk updates from Petr Mladek:

 - Add a console_msg_format command line option:

     The value "default" keeps the old "[time stamp] text\n" format. The
     value "syslog" allows to see the syslog-like "<log
     level>[timestamp] text" format.

     This feature was requested by people doing regression tests, for
     example, 0day robot. They want to have both filtered and full logs
     at hands.

 - Reduce the risk of softlockup:

     Pass the console owner in a busy loop.

     This is a new approach to the old problem. It was first proposed by
     Steven Rostedt on Kernel Summit 2017. It marks a context in which
     the console_lock owner calls console drivers and could not sleep.
     On the other side, printk() callers could detect this state and use
     a busy wait instead of a simple console_trylock(). Finally, the
     console_lock owner checks if there is a busy waiter at the end of
     the special context and eventually passes the console_lock to the
     waiter.

     The hand-off works surprisingly well and helps in many situations.
     Well, there is still a possibility of the softlockup, for example,
     when the flood of messages stops and the last owner still has too
     much to flush.

     There is increasing number of people having problems with
     printk-related softlockups. We might eventually need to get better
     solution. Anyway, this looks like a good start and promising
     direction.

 - Do not allow to schedule in console_unlock() called from printk():

     This reverts an older controversial commit. The reschedule helped
     to avoid softlockups. But it also slowed down the console output.
     This patch is obsoleted by the new console waiter logic described
     above. In fact, the reschedule made the hand-off less effective.

 - Deprecate "%pf" and "%pF" format specifier:

     It was needed on ia64, ppc64 and parisc64 to dereference function
     descriptors and show the real function address. It is done
     transparently by "%ps" and "pS" format specifier now.

     Sergey Senozhatsky found that all the function descriptors were in
     a special elf section and could be easily detected.

 - Remove printk_symbol() API:

     It has been obsoleted by "%pS" format specifier, and this change
     helped to remove few continuous lines and a less intuitive old API.

 - Remove redundant memsets:

     Sergey removed unnecessary memset when processing printk.devkmsg
     command line option.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (27 commits)
  printk: drop redundant devkmsg_log_str memsets
  printk: Never set console_may_schedule in console_trylock()
  printk: Hide console waiter logic into helpers
  printk: Add console owner and waiter logic to load balance console writes
  kallsyms: remove print_symbol() function
  checkpatch: add pF/pf deprecation warning
  symbol lookup: introduce dereference_symbol_descriptor()
  parisc64: Add .opd based function descriptor dereference
  powerpc64: Add .opd based function descriptor dereference
  ia64: Add .opd based function descriptor dereference
  sections: split dereference_function_descriptor()
  openrisc: Fix conflicting types for _exext and _stext
  lib: do not use print_symbol()
  irq debug: do not use print_symbol()
  sysfs: do not use print_symbol()
  drivers: do not use print_symbol()
  x86: do not use print_symbol()
  unicore32: do not use print_symbol()
  sh: do not use print_symbol()
  mn10300: do not use print_symbol()
  ...

Pull dma mapping updates from Christoph Hellwig:
 "Except for a runtime warning fix from Christian this is all about
  consolidation of the generic no-IOMMU code, a well as the glue code
  for swiotlb.

  All the code is based on the x86 implementation with hooks to allow
  all architectures that aren't cache coherent to use it.

  The x86 conversion itself has been deferred because the x86
  maintainers were a little busy in the last months"

* tag 'dma-mapping-4.16' of git://git.infradead.org/users/hch/dma-mapping: (57 commits)
  MAINTAINERS: add the iommu list for swiotlb and xen-swiotlb
  arm64: use swiotlb_alloc and swiotlb_free
  arm64: replace ZONE_DMA with ZONE_DMA32
  mips: use swiotlb_{alloc,free}
  mips/netlogic: remove swiotlb support
  tile: use generic swiotlb_ops
  tile: replace ZONE_DMA with ZONE_DMA32
  unicore32: use generic swiotlb_ops
  ia64: remove an ifdef around the content of pci-dma.c
  ia64: clean up swiotlb support
  ia64: use generic swiotlb_ops
  ia64: replace ZONE_DMA with ZONE_DMA32
  swiotlb: remove various exports
  swiotlb: refactor coherent buffer allocation
  swiotlb: refactor coherent buffer freeing
  swiotlb: wire up ->dma_supported in swiotlb_dma_ops
  swiotlb: add common swiotlb_map_ops
  swiotlb: rename swiotlb_free to swiotlb_exit
  x86: rename swiotlb_dma_ops
  powerpc: rename swiotlb_dma_ops
  ...