We currently try to shrink a single zone when removing memory.  We use
the zone of the first page of the memory we are removing.  If that
memmap was never initialized (e.g., memory was never onlined), we will
read garbage and can trigger kernel BUGs (due to a stale pointer):

    BUG: unable to handle page fault for address: 000000000000353d
    #PF: supervisor write access in kernel mode
    #PF: error_code(0x0002) - not-present page
    PGD 0 P4D 0
    Oops: 0002 [#1] SMP PTI
    CPU: 1 PID: 7 Comm: kworker/u8:0 Not tainted 5.3.0-rc5-next-20190820+ #317
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.4
    Workqueue: kacpi_hotplug acpi_hotplug_work_fn
    RIP: 0010:clear_zone_contiguous+0x5/0x10
    Code: 48 89 c6 48 89 c3 e8 2a fe ff ff 48 85 c0 75 cf 5b 5d c3 c6 85 fd 05 00 00 01 5b 5d c3 0f 1f 840
    RSP: 0018:ffffad2400043c98 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: 0000000200000000 RCX: 0000000000000000
    RDX: 0000000000200000 RSI: 0000000000140000 RDI: 0000000000002f40
    RBP: 0000000140000000 R08: 0000000000000000 R09: 0000000000000001
    R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000140000
    R13: 0000000000140000 R14: 0000000000002f40 R15: ffff9e3e7aff3680
    FS:  0000000000000000(0000) GS:ffff9e3e7bb00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 000000000000353d CR3: 0000000058610000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     __remove_pages+0x4b/0x640
     arch_remove_memory+0x63/0x8d
     try_remove_memory+0xdb/0x130
     __remove_memory+0xa/0x11
     acpi_memory_device_remove+0x70/0x100
     acpi_bus_trim+0x55/0x90
     acpi_device_hotplug+0x227/0x3a0
     acpi_hotplug_work_fn+0x1a/0x30
     process_one_work+0x221/0x550
     worker_thread+0x50/0x3b0
     kthread+0x105/0x140
     ret_from_fork+0x3a/0x50
    Modules linked in:
    CR2: 000000000000353d

Instead, shrink the zones when offlining memory or when onlining failed.
Introduce and use remove_pfn_range_from_zone(() for that.  We now
properly shrink the zones, even if we have DIMMs whereby

 - Some memory blocks fall into no zone (never onlined)

 - Some memory blocks fall into multiple zones (offlined+re-onlined)

 - Multiple memory blocks that fall into different zones

Drop the zone parameter (with a potential dubious value) from
__remove_pages() and __remove_section().

Link: http://lkml.kernel.org/r/20191006085646.5768-6-david@redhat.com
Fixes: f1dd2cd13c4b ("mm, memory_hotplug: do not associate hotadded memory to zones until online")	[visible after d0dc12e86b319]
Signed-off-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Logan Gunthorpe <logang@deltatee.com>
Cc: <stable@vger.kernel.org>	[5.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Pull more drm updates from Dave Airlie:
 "Rob pointed out I missed his pull request for msm-next, it's been in
  next for a while outside of my tree so shouldn't cause any unexpected
  issues, it has some OCMEM support in drivers/soc that is acked by
  other maintainers as it's outside my tree.

  Otherwise it's a usual fixes pull, i915, amdgpu, the main ones, with
  some tegra, omap, mgag200 and one core fix.

  Summary:

  msm-next:
   - OCMEM support for a3xx and a4xx GPUs.
   - a510 support + display support

  core:
   - mst payload deletion fix

  i915:
   - uapi alignment fix
   - fix for power usage regression due to security fixes
   - change default preemption timeout to 640ms from 100ms
   - EHL voltage level display fixes
   - TGL DGL PHY fix
   - gvt - MI_ATOMIC cmd parser fix, CFL non-priv warning
   - CI spotted deadlock fix
   - EHL port D programming fix

  amdgpu:
   - VRAM lost fixes on BACO for CI/VI
   - navi14 DC fixes
   - misc SR-IOV, gfx10 fixes
   - XGMI fixes for arcturus
   - SRIOV fixes

  amdkfd:
   - KFD on ppc64le enabled
   - page table optimisations

  radeon:
   - fix for r1xx/2xx register checker.

  tegra:
   - displayport regression fixes
   - DMA API regression fixes

  mgag200:
   - fix devices that can't scanout except at 0 addr

  omap:
   - fix dma_addr refcounting"

* tag 'drm-next-2019-12-06' of git://anongit.freedesktop.org/drm/drm: (100 commits)
  drm/dp_mst: Correct the bug in drm_dp_update_payload_part1()
  drm/omap: fix dma_addr refcounting
  drm/tegra: Run hub cleanup on ->remove()
  drm/tegra: sor: Make the +5V HDMI supply optional
  drm/tegra: Silence expected errors on IOMMU attach
  drm/tegra: vic: Export module device table
  drm/tegra: sor: Implement system suspend/resume
  drm/tegra: Use proper IOVA address for cursor image
  drm/tegra: gem: Remove premature import restrictions
  drm/tegra: gem: Properly pin imported buffers
  drm/tegra: hub: Remove bogus connection mutex check
  ia64: agp: Replace empty define with do while
  agp: Add bridge parameter documentation
  agp: remove unused variable num_segments
  agp: move AGPGART_MINOR to include/linux/miscdevice.h
  agp: remove unused variable size in agp_generic_create_gatt_table
  drm/dp_mst: Fix build on systems with STACKTRACE_SUPPORT=n
  drm/radeon: fix r1xx/r2xx register checker for POT textures
  drm/amdgpu: fix GFX10 missing CSIB set(v3)
  drm/amdgpu: should stop GFX ring in hw_fini
  ...

Pull ia64 update from Tony Luck:
 "Cleanup some leftover para-virtualization pieces"

* tag 'please-pull-misc-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux:
  ia64: remove stale paravirt leftovers

It's dangerous to use empty code define.
Furthermore it lead to the following warning:
drivers/char/agp/generic.c: In function « agp_generic_destroy_page »:
drivers/char/agp/generic.c:1266:28: attention : suggest braces around empty body in an « if » statement [-Wempty-body]

So let's replace emptyness by "do {} while(0)"

Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1574324085-4338-6-git-send-email-clabbe@baylibre.com

Pull Kbuild updates from Masahiro Yamada:

 - remove unneeded asm headers from hexagon, ia64

 - add 'dir-pkg' target, which works like 'tar-pkg' but skips archiving

 - add 'helpnewconfig' target, which shows help for new CONFIG options

 - support 'make nsdeps' for external modules

 - make rebuilds faster by deleting $(wildcard $^) checks

 - remove compile tests for kernel-space headers

 - refactor modpost to simplify modversion handling

 - make single target builds faster

 - optimize and clean up scripts/kallsyms.c

 - refactor various Makefiles and scripts

* tag 'kbuild-v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (59 commits)
  MAINTAINERS: update Kbuild/Kconfig maintainer's email address
  scripts/kallsyms: remove redundant initializers
  scripts/kallsyms: put check_symbol_range() calls close together
  scripts/kallsyms: make check_symbol_range() void function
  scripts/kallsyms: move ignored symbol types to is_ignored_symbol()
  scripts/kallsyms: move more patterns to the ignored_prefixes array
  scripts/kallsyms: skip ignored symbols very early
  scripts/kallsyms: add const qualifiers where possible
  scripts/kallsyms: make find_token() return (unsigned char *)
  scripts/kallsyms: replace prefix_underscores_count() with strspn()
  scripts/kallsyms: add sym_name() to mitigate cast ugliness
  scripts/kallsyms: remove unneeded length check for prefix matching
  scripts/kallsyms: remove redundant is_arm_mapping_symbol()
  scripts/kallsyms: set relative_base more effectively
  scripts/kallsyms: shrink table before sorting it
  scripts/kallsyms: fix definitely-lost memory leak
  scripts/kallsyms: remove unneeded #ifndef ARRAY_SIZE
  kbuild: make single target builds even faster
  modpost: respect the previous export when 'exported twice' is warned
  modpost: do not set ->preloaded for symbols from Module.symvers
  ...

Remove the last leftovers from IA64 Xen pv-guest support.

PARAVIRT is long gone from IA64 Kconfig and Xen IA64 support, too.

Due to lack of infrastructure no testing done.

Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lore.kernel.org/r/20191021100415.7642-1-jgross@suse.com

Pull iommu updates from Joerg Roedel:

 - Conversion of the AMD IOMMU driver to use the dma-iommu code for
   imlementing the DMA-API. This gets rid of quite some code in the
   driver itself, but also has some potential for regressions (non are
   known at the moment).

 - Support for the Qualcomm SMMUv2 implementation in the SDM845 SoC.
   This also includes some firmware interface changes, but those are
   acked by the respective maintainers.

 - Preparatory work to support two distinct page-tables per domain in
   the ARM-SMMU driver

 - Power management improvements for the ARM SMMUv2

 - Custom PASID allocator support

 - Multiple PCI DMA alias support for the AMD IOMMU driver

 - Adaption of the Mediatek driver to the changed IO/TLB flush interface
   of the IOMMU core code.

 - Preparatory patches for the Renesas IOMMU driver to support future
   hardware.

* tag 'iommu-updates-v5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu: (62 commits)
  iommu/rockchip: Don't provoke WARN for harmless IRQs
  iommu/vt-d: Turn off translations at shutdown
  iommu/vt-d: Check VT-d RMRR region in BIOS is reported as reserved
  iommu/arm-smmu: Remove duplicate error message
  iommu/arm-smmu-v3: Don't display an error when IRQ lines are missing
  iommu/ipmmu-vmsa: Add utlb_offset_base
  iommu/ipmmu-vmsa: Add helper functions for "uTLB" registers
  iommu/ipmmu-vmsa: Calculate context registers' offset instead of a macro
  iommu/ipmmu-vmsa: Add helper functions for MMU "context" registers
  iommu/ipmmu-vmsa: tidyup register definitions
  iommu/ipmmu-vmsa: Remove all unused register definitions
  iommu/mediatek: Reduce the tlb flush timeout value
  iommu/mediatek: Get rid of the pgtlock
  iommu/mediatek: Move the tlb_sync into tlb_flush
  iommu/mediatek: Delete the leaf in the tlb_flush
  iommu/mediatek: Use gather to achieve the tlb range flush
  iommu/mediatek: Add a new tlb_lock for tlb_flush
  iommu/mediatek: Correct the flush_iotlb_all callback
  iommu/io-pgtable-arm: Rename IOMMU_QCOM_SYS_CACHE and improve doc
  iommu/io-pgtable-arm: Rationalise MAIR handling
  ...

Pull y2038 cleanups from Arnd Bergmann:
 "y2038 syscall implementation cleanups

  This is a series of cleanups for the y2038 work, mostly intended for
  namespace cleaning: the kernel defines the traditional time_t, timeval
  and timespec types that often lead to y2038-unsafe code. Even though
  the unsafe usage is mostly gone from the kernel, having the types and
  associated functions around means that we can still grow new users,
  and that we may be missing conversions to safe types that actually
  matter.

  There are still a number of driver specific patches needed to get the
  last users of these types removed, those have been submitted to the
  respective maintainers"

Link: https://lore.kernel.org/lkml/20191108210236.1296047-1-arnd@arndb.de/

* tag 'y2038-cleanups-5.5' of git://git.kernel.org:/pub/scm/linux/kernel/git/arnd/playground: (26 commits)
  y2038: alarm: fix half-second cut-off
  y2038: ipc: fix x32 ABI breakage
  y2038: fix typo in powerpc vdso "LOPART"
  y2038: allow disabling time32 system calls
  y2038: itimer: change implementation to timespec64
  y2038: move itimer reset into itimer.c
  y2038: use compat_{get,set}_itimer on alpha
  y2038: itimer: compat handling to itimer.c
  y2038: time: avoid timespec usage in settimeofday()
  y2038: timerfd: Use timespec64 internally
  y2038: elfcore: Use __kernel_old_timeval for process times
  y2038: make ns_to_compat_timeval use __kernel_old_timeval
  y2038: socket: use __kernel_old_timespec instead of timespec
  y2038: socket: remove timespec reference in timestamping
  y2038: syscalls: change remaining timeval to __kernel_old_timeval
  y2038: rusage: use __kernel_old_timeval
  y2038: uapi: change __kernel_time_t to __kernel_old_time_t
  y2038: stat: avoid 'time_t' in 'struct stat'
  y2038: ipc: remove __kernel_time_t reference from headers
  y2038: vdso: powerpc: avoid timespec references
  ...

Pull dma-mapping updates from Christoph Hellwig:

 - improve dma-debug scalability (Eric Dumazet)

 - tiny dma-debug cleanup (Dan Carpenter)

 - check for vmap memory in dma_map_single (Kees Cook)

 - check for dma_addr_t overflows in dma-direct when using DMA offsets
   (Nicolas Saenz Julienne)

 - switch the x86 sta2x11 SOC to use more generic DMA code (Nicolas
   Saenz Julienne)

 - fix arm-nommu dma-ranges handling (Vladimir Murzin)

 - use __initdata in CMA (Shyam Saini)

 - replace the bus dma mask with a limit (Nicolas Saenz Julienne)

 - merge the remapping helpers into the main dma-direct flow (me)

 - switch xtensa to the generic dma remap handling (me)

 - various cleanups around dma_capable (me)

 - remove unused dev arguments to various dma-noncoherent helpers (me)

* 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux:

* tag 'dma-mapping-5.5' of git://git.infradead.org/users/hch/dma-mapping: (22 commits)
  dma-mapping: treat dev->bus_dma_mask as a DMA limit
  dma-direct: exclude dma_direct_map_resource from the min_low_pfn check
  dma-direct: don't check swiotlb=force in dma_direct_map_resource
  dma-debug: clean up put_hash_bucket()
  powerpc: remove support for NULL dev in __phys_to_dma / __dma_to_phys
  dma-direct: avoid a forward declaration for phys_to_dma
  dma-direct: unify the dma_capable definitions
  dma-mapping: drop the dev argument to arch_sync_dma_for_*
  x86/PCI: sta2x11: use default DMA address translation
  dma-direct: check for overflows on 32 bit DMA addresses
  dma-debug: increase HASH_SIZE
  dma-debug: reorder struct dma_debug_entry fields
  xtensa: use the generic uncached segment support
  dma-mapping: merge the generic remapping helpers into dma-direct
  dma-direct: provide mmap and get_sgtable method overrides
  dma-direct: remove the dma_handle argument to __dma_direct_alloc_pages
  dma-direct: remove __dma_direct_free_pages
  usb: core: Remove redundant vmap checks
  kernel: dma-contiguous: mark CMA parameters __initdata/__initconst
  dma-debug: add a schedule point in debug_dma_dump_mappings()
  ...

Pull generic ioremap support from Christoph Hellwig:
 "This adds the remaining bits for an entirely generic ioremap and
  iounmap to lib/ioremap.c. To facilitate that, it cleans up the giant
  mess of weird ioremap variants we had with no users outside the arch
  code.

  For now just the three newest ports use the code, but there is more
  than a handful others that can be converted without too much work.

  Summary:

   - clean up various obsolete ioremap and iounmap variants

   - add a new generic ioremap implementation and switch csky, nds32 and
     riscv over to it"

* tag 'ioremap-5.5' of git://git.infradead.org/users/hch/ioremap: (21 commits)
  nds32: use generic ioremap
  csky: use generic ioremap
  csky: remove ioremap_cache
  riscv: use the generic ioremap code
  lib: provide a simple generic ioremap implementation
  sh: remove __iounmap
  nios2: remove __iounmap
  hexagon: remove __iounmap
  m68k: rename __iounmap and mark it static
  arch: rely on asm-generic/io.h for default ioremap_* definitions
  asm-generic: don't provide ioremap for CONFIG_MMU
  asm-generic: ioremap_uc should behave the same with and without MMU
  xtensa: clean up ioremap
  x86: Clean up ioremap()
  parisc: remove __ioremap
  nios2: remove __ioremap
  alpha: remove the unused __ioremap wrapper
  hexagon: clean up ioremap
  ia64: rename ioremap_nocache to ioremap_uc
  unicore32: remove ioremap_cached
  ...