linux-stable.git/arch/powerpc/include/asm/pgtable.h, branch linux-4.7.y

arch: fix has_transparent_hugepage()

2016-05-20T02:12:14+00:00

I've just discovered that the useful-sounding has_transparent_hugepage()
is actually an architecture-dependent minefield: on some arches it only
builds if CONFIG_TRANSPARENT_HUGEPAGE=y, on others it's also there when
not, but on some of those (arm and arm64) it then gives the wrong
answer; and on mips alone it's marked __init, which would crash if
called later (but so far it has not been called later).

Straighten this out: make it available to all configs, with a sensible
default in asm-generic/pgtable.h, removing its definitions from those
arches (arc, arm, arm64, sparc, tile) which are served by the default,
adding #define has_transparent_hugepage has_transparent_hugepage to
those (mips, powerpc, s390, x86) which need to override the default at
runtime, and removing the __init from mips (but maybe that kind of code
should be avoided after init: set a static variable the first time it's
called).

Signed-off-by: Hugh Dickins 
Cc: "Kirill A. Shutemov" 
Cc: Andrea Arcangeli 
Cc: Andres Lagar-Cavilla 
Cc: Yang Shi 
Cc: Ning Qu 
Cc: Mel Gorman 
Cc: Konstantin Khlebnikov 
Acked-by: David S. Miller 
Acked-by: Vineet Gupta 		[arch/arc]
Acked-by: Gerald Schaefer 	[arch/s390]
Acked-by: Ingo Molnar 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

powerpc: Make vmalloc_to_phys() public

2016-02-16T02:44:26+00:00

This makes vmalloc_to_phys() public as there will be another user
(KVM in-kernel VFIO acceleration) for it soon. As this new user
can be compiled as a module, this exports the symbol.

As a little optimization, this changes the helper to call
vmalloc_to_pfn() instead of vmalloc_to_page() as the size of the
struct page may not be power-of-two aligned which will make gcc use
multiply instructions instead of shifts.

Signed-off-by: Alexey Kardashevskiy 
Acked-by: Michael Ellerman 
Reviewed-by: David Gibson 
Signed-off-by: Paul Mackerras

powerpc/booke: Move nohash headers

2015-12-14T04:19:09+00:00

Move the booke related headers below booke/32 or booke/64

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

powerpc/mm: Move hash64 PTE bits from book3s/64/pgtable.h to hash.h

2015-12-14T04:19:08+00:00

This enables us to keep hash64 related bits together, and makes it easy
to follow.

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

powerpc/mm: Don't have generic headers introduce functions touching pte bits

2015-12-14T04:19:06+00:00

We are going to drop pte_common.h in the later patch. The idea is to
enable hash code not require to define all PTE bits. Having PTE bits
defined in pte_common.h made the code unnecessarily complex.

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

powerpc/mm: make a separate copy for book3s

2015-12-14T04:19:05+00:00

In this patch we do:
cp pgtable-ppc32.h book3s/32/pgtable.h
cp pgtable-ppc64.h book3s/64/pgtable.h

This enable us to do further changes to hash specific config.
We will change the page table format for 64bit hash in later patches.

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

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