linux-toradex.git/arch/powerpc/include/asm/pgtable.h, branch v4.4.65

powerpc/mm: Differentiate between hugetlb and THP during page walk

2015-10-12T04:30:09+00:00

We need to properly identify whether a hugepage is an explicit or
a transparent hugepage in follow_huge_addr(). We used to depend
on hugepage shift argument to do that. But in some case that can
result in wrong results. For ex:

On finding a transparent hugepage we set hugepage shift to PMD_SHIFT.
But we can end up clearing the thp pte, via pmdp_huge_get_and_clear.
We do prevent reusing the pfn page via the usage of
kick_all_cpus_sync(). But that happens after we updated the pte to 0.
Hence in follow_huge_addr() we can find hugepage shift set, but transparent
huge page check fail for a thp pte.

NOTE: We fixed a variant of this race against thp split in commit
691e95fd7396905a38d98919e9c150dbc3ea21a3
("powerpc/mm/thp: Make page table walk safe against thp split/collapse")

Without this patch, we may hit the BUG_ON(flags & FOLL_GET) in
follow_page_mask occasionally.

In the long term, we may want to switch ppc64 64k page size config to
enable CONFIG_ARCH_WANT_GENERAL_HUGETLB

Reported-by: David Gibson 
Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Michael Ellerman

powerpc/booke64: Move mb() to __set_pte_at() with kernel-addr test

2015-08-08T04:00:01+00:00

map_kernel() doesn't catch all places that create kernel PTEs.  In
particular, vmalloc() calls set_pte_at() directly.  This causes a
crash when booting a non-SMP kernel on e6500.

Move the sync to __set_pte(), to be executed only for kernel addresses.

Signed-off-by: Scott Wood

powerpc/mm/thp: Make page table walk safe against thp split/collapse

2015-04-17T01:23:39+00:00

We can disable a THP split or a hugepage collapse by disabling irq.
We do send IPI to all the cpus in the early part of split/collapse,
and disabling local irq ensure we don't make progress with
split/collapse. If the THP is getting split we return NULL from
find_linux_pte_or_hugepte(). For all the current callers it should be ok.
We need to be careful if we want to use returned pte_t pointer outside
the irq disabled region. W.r.t to THP split, the pfn remains the same,
but then a hugepage collapse will result in a pfn change. There are
few steps we can take to avoid a hugepage collapse.One way is to take page
reference inside the irq disable region. Other option is to take
mmap_sem so that a parallel collapse will not happen. We can also
disable collapse by taking pmd_lock. Another method used by kvm
subsystem is to check whether we had a mmu_notifer update in between
using mmu_notifier_retry().

Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Michael Ellerman

KVM: PPC: Remove page table walk helpers

2015-04-17T01:23:24+00:00

This patch remove helpers which we had used only once in the code.
Limiting page table walk variants help in ensuring that we won't
end up with code walking page table with wrong assumptions.

Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Michael Ellerman

powerpc: drop _PAGE_FILE and pte_file()-related helpers

2015-02-17T01:56:05+00:00

We've replaced remap_file_pages(2) implementation with emulation.  Nobody
creates non-linear mapping anymore.

Signed-off-by: Kirill A. Shutemov 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Michael Ellerman 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: remove remaining references to NUMA hinting bits and helpers

2015-02-13T02:54:08+00:00

This patch removes the NUMA PTE bits and associated helpers.  As a
side-effect it increases the maximum possible swap space on x86-64.

One potential source of problems is races between the marking of PTEs
PROT_NONE, NUMA hinting faults and migration.  It must be guaranteed that
a PTE being protected is not faulted in parallel, seen as a pte_none and
corrupting memory.  The base case is safe but transhuge has problems in
the past due to an different migration mechanism and a dependance on page
lock to serialise migrations and warrants a closer look.

task_work hinting update			parallel fault
------------------------			--------------
change_pmd_range
  change_huge_pmd
    __pmd_trans_huge_lock
      pmdp_get_and_clear
						__handle_mm_fault
						pmd_none
						  do_huge_pmd_anonymous_page
						  read? pmd_lock blocks until hinting complete, fail !pmd_none test
						  write? __do_huge_pmd_anonymous_page acquires pmd_lock, checks pmd_none
      pmd_modify
      set_pmd_at

task_work hinting update			parallel migration
------------------------			------------------
change_pmd_range
  change_huge_pmd
    __pmd_trans_huge_lock
      pmdp_get_and_clear
						__handle_mm_fault
						  do_huge_pmd_numa_page
						    migrate_misplaced_transhuge_page
						    pmd_lock waits for updates to complete, recheck pmd_same
      pmd_modify
      set_pmd_at

Both of those are safe and the case where a transhuge page is inserted
during a protection update is unchanged.  The case where two processes try
migrating at the same time is unchanged by this series so should still be
ok.  I could not find a case where we are accidentally depending on the
PTE not being cleared and flushed.  If one is missed, it'll manifest as
corruption problems that start triggering shortly after this series is
merged and only happen when NUMA balancing is enabled.

Signed-off-by: Mel Gorman 
Tested-by: Sasha Levin 
Cc: Aneesh Kumar K.V 
Cc: Benjamin Herrenschmidt 
Cc: Dave Jones 
Cc: Hugh Dickins 
Cc: Ingo Molnar 
Cc: Kirill Shutemov 
Cc: Linus Torvalds 
Cc: Paul Mackerras 
Cc: Rik van Riel 
Cc: Mark Brown 
Cc: Stephen Rothwell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm: add p[te|md] protnone helpers for use by NUMA balancing

2015-02-13T02:54:08+00:00

This is a preparatory patch that introduces protnone helpers for automatic
NUMA balancing.

Signed-off-by: Mel Gorman 
Acked-by: Linus Torvalds 
Acked-by: Aneesh Kumar K.V 
Tested-by: Sasha Levin 
Cc: Benjamin Herrenschmidt 
Cc: Dave Jones 
Cc: Hugh Dickins 
Cc: Ingo Molnar 
Cc: Kirill Shutemov 
Cc: Paul Mackerras 
Cc: Rik van Riel 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

powerpc32: adds handling of _PAGE_RO

2015-01-30T02:11:51+00:00

Some powerpc like the 8xx don't have a RW bit in PTE bits but a RO
(Read Only) bit.  This patch implements the handling of a _PAGE_RO flag
to be used in place of _PAGE_RW

Signed-off-by: Christophe Leroy 
[scottwood@freescale.com: fix whitespace]
Signed-off-by: Scott Wood

powerpc/mm: Switch to generic RCU get_user_pages_fast

2014-11-14T06:24:21+00:00

This patch switch the ppc arch to use the generic RCU based
gup implementation.

Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Michael Ellerman

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux

2014-10-12T00:34:00+00:00

Pull powerpc updates from Michael Ellerman:
 "Here's a first pull request for powerpc updates for 3.18.

  The bulk of the additions are for the "cxl" driver, for IBM's Coherent
  Accelerator Processor Interface (CAPI).  Most of it's in drivers/misc,
  which Greg & Arnd maintain, Greg said he was happy for us to take it
  through our tree.

  There's the usual minor cleanups and fixes, including a bit of noise
  in drivers from some of those.  A bunch of updates to our EEH code,
  which has been getting more testing.  Several nice speedups from
  Anton, including 20% in clear_page().

  And a bunch of updates for freescale from Scott"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux: (130 commits)
  cxl: Fix afu_read() not doing finish_wait() on signal or non-blocking
  cxl: Add documentation for userspace APIs
  cxl: Add driver to Kbuild and Makefiles
  cxl: Add userspace header file
  cxl: Driver code for powernv PCIe based cards for userspace access
  cxl: Add base builtin support
  powerpc/mm: Add hooks for cxl
  powerpc/opal: Add PHB to cxl mode call
  powerpc/mm: Add new hash_page_mm()
  powerpc/powerpc: Add new PCIe functions for allocating cxl interrupts
  cxl: Add new header for call backs and structs
  powerpc/powernv: Split out set MSI IRQ chip code
  powerpc/mm: Export mmu_kernel_ssize and mmu_linear_psize
  powerpc/msi: Improve IRQ bitmap allocator
  powerpc/cell: Make spu_flush_all_slbs() generic
  powerpc/cell: Move data segment faulting code out of cell platform
  powerpc/cell: Move spu_handle_mm_fault() out of cell platform
  powerpc/pseries: Use new defines when calling H_SET_MODE
  powerpc: Update contact info in Documentation files
  powerpc/perf/hv-24x7: Simplify catalog_read()
  ...