linux-toradex.git/arch/powerpc/mm, branch v3.10.92

vm: add VM_FAULT_SIGSEGV handling support

2015-04-29T08:34:00+00:00

commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream.

The core VM already knows about VM_FAULT_SIGBUS, but cannot return a
"you should SIGSEGV" error, because the SIGSEGV case was generally
handled by the caller - usually the architecture fault handler.

That results in lots of duplication - all the architecture fault
handlers end up doing very similar "look up vma, check permissions, do
retries etc" - but it generally works.  However, there are cases where
the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV.

In particular, when accessing the stack guard page, libsigsegv expects a
SIGSEGV.  And it usually got one, because the stack growth is handled by
that duplicated architecture fault handler.

However, when the generic VM layer started propagating the error return
from the stack expansion in commit fee7e49d4514 ("mm: propagate error
from stack expansion even for guard page"), that now exposed the
existing VM_FAULT_SIGBUS result to user space.  And user space really
expected SIGSEGV, not SIGBUS.

To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those
duplicate architecture fault handlers about it.  They all already have
the code to handle SIGSEGV, so it's about just tying that new return
value to the existing code, but it's all a bit annoying.

This is the mindless minimal patch to do this.  A more extensive patch
would be to try to gather up the mostly shared fault handling logic into
one generic helper routine, and long-term we really should do that
cleanup.

Just from this patch, you can generally see that most architectures just
copied (directly or indirectly) the old x86 way of doing things, but in
the meantime that original x86 model has been improved to hold the VM
semaphore for shorter times etc and to handle VM_FAULT_RETRY and other
"newer" things, so it would be a good idea to bring all those
improvements to the generic case and teach other architectures about
them too.

Reported-and-tested-by: Takashi Iwai 
Tested-by: Jan Engelhardt 
Acked-by: Heiko Carstens  # "s390 still compiles and boots"
Cc: linux-arch@vger.kernel.org
Signed-off-by: Linus Torvalds 
[shengyong: Backport to 3.10
 - adjust context
 - ignore modification for arch nios2, because 3.10 does not support it
 - ignore modification for driver lustre, because 3.10 does not support it
 - ignore VM_FAULT_FALLBACK in VM_FAULT_ERROR, becase 3.10 does not support
   this flag
 - add SIGSEGV handling to powerpc/cell spu_fault.c, because 3.10 does not
   separate it to copro_fault.c
 - add SIGSEGV handling in mm/memory.c, because 3.10 does not separate it
   to gup.c
]
Signed-off-by: Sheng Yong 
Signed-off-by: Greg Kroah-Hartman

arch: mm: pass userspace fault flag to generic fault handler

2014-11-21T17:22:56+00:00

commit 759496ba6407c6994d6a5ce3a5e74937d7816208 upstream.

Unlike global OOM handling, memory cgroup code will invoke the OOM killer
in any OOM situation because it has no way of telling faults occuring in
kernel context - which could be handled more gracefully - from
user-triggered faults.

Pass a flag that identifies faults originating in user space from the
architecture-specific fault handlers to generic code so that memcg OOM
handling can be improved.

Signed-off-by: Johannes Weiner 
Reviewed-by: Michal Hocko 
Cc: David Rientjes 
Cc: KAMEZAWA Hiroyuki 
Cc: azurIt 
Cc: KOSAKI Motohiro 
Signed-off-by: Andrew Morton 
Signed-off-by: Cong Wang 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

powerpc/mm/numa: Fix break placement

2014-09-17T16:03:57+00:00

commit b00fc6ec1f24f9d7af9b8988b6a198186eb3408c upstream.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=81631
Reported-by: David Binderman 
Signed-off-by: Andrey Utkin 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: Fix the setup of CPU-to-Node mappings during CPU online

2014-02-06T19:08:18+00:00

commit d4edc5b6c480a0917e61d93d55531d7efa6230be upstream.

On POWER platforms, the hypervisor can notify the guest kernel about dynamic
changes in the cpu-numa associativity (VPHN topology update). Hence the
cpu-to-node mappings that we got from the firmware during boot, may no longer
be valid after such updates. This is handled using the arch_update_cpu_topology()
hook in the scheduler, and the sched-domains are rebuilt according to the new
mappings.

But unfortunately, at the moment, CPU hotplug ignores these updated mappings
and instead queries the firmware for the cpu-to-numa relationships and uses
them during CPU online. So the kernel can end up assigning wrong NUMA nodes
to CPUs during subsequent CPU hotplug online operations (after booting).

Further, a particularly problematic scenario can result from this bug:
On POWER platforms, the SMT mode can be switched between 1, 2, 4 (and even 8)
threads per core. The switch to Single-Threaded (ST) mode is performed by
offlining all except the first CPU thread in each core. Switching back to
SMT mode involves onlining those other threads back, in each core.

Now consider this scenario:

1. During boot, the kernel gets the cpu-to-node mappings from the firmware
   and assigns the CPUs to NUMA nodes appropriately, during CPU online.

2. Later on, the hypervisor updates the cpu-to-node mappings dynamically and
   communicates this update to the kernel. The kernel in turn updates its
   cpu-to-node associations and rebuilds its sched domains. Everything is
   fine so far.

3. Now, the user switches the machine from SMT to ST mode (say, by running
   ppc64_cpu --smt=1). This involves offlining all except 1 thread in each
   core.

4. The user then tries to switch back from ST to SMT mode (say, by running
   ppc64_cpu --smt=4), and this involves onlining those threads back. Since
   CPU hotplug ignores the new mappings, it queries the firmware and tries to
   associate the newly onlined sibling threads to the old NUMA nodes. This
   results in sibling threads within the same core getting associated with
   different NUMA nodes, which is incorrect.

   The scheduler's build-sched-domains code gets thoroughly confused with this
   and enters an infinite loop and causes soft-lockups, as explained in detail
   in commit 3be7db6ab (powerpc: VPHN topology change updates all siblings).

So to fix this, use the numa_cpu_lookup_table to remember the updated
cpu-to-node mappings, and use them during CPU hotplug online operations.
Further, we also need to ensure that all threads in a core are assigned to a
common NUMA node, irrespective of whether all those threads were online during
the topology update. To achieve this, we take care not to use cpu_sibling_mask()
since it is not hotplug invariant. Instead, we use cpu_first_sibling_thread()
and set up the mappings manually using the 'threads_per_core' value for that
particular platform. This helps us ensure that we don't hit this bug with any
combination of CPU hotplug and SMT mode switching.

Signed-off-by: Srivatsa S. Bhat 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: ppc64 address space capped at 32TB, mmap randomisation disabled

2013-11-29T19:11:51+00:00

commit 5a049f14902982c26538250bdc8d54156d357252 upstream.

Commit fba2369e6ceb (mm: use vm_unmapped_area() on powerpc architecture)
has a bug in slice_scan_available() where we compare an unsigned long
(high_slices) against a shifted int. As a result, comparisons against
the top 32 bits of high_slices (representing the top 32TB) always
returns 0 and the top of our mmap region is clamped at 32TB

This also breaks mmap randomisation since the randomised address is
always up near the top of the address space and it gets clamped down
to 32TB.

Signed-off-by: Anton Blanchard 
Acked-by: Michel Lespinasse 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: VPHN topology change updates all siblings

2013-08-12T01:35:20+00:00

commit 3be7db6ab45b21345386d1a466da133b19cde5e4 upstream.

When an associativity level change is found for one thread, the
siblings threads need to be updated as well.  This is done today
for PRRN in stage_topology_update() but is missing for VPHN in
update_cpu_associativity_changes_mask().  This patch will correctly
update all thread siblings during a topology change.

Without this patch a topology update can result in a CPU in
init_sched_groups_power() getting stuck indefinitely in a loop.

This loop is built in build_sched_groups(). As a result of the thread
moving to a node separate from its siblings the struct sched_group will
have its next pointer set to point to itself rather than the sched_group
struct of the next thread.  This happens because we have a domain without
the SD_OVERLAP flag, which is correct, and a topology that doesn't conform
with reality (threads on the same core assigned to different numa nodes).
When this list is traversed by init_sched_groups_power() it will reach
the thread's sched_group structure and loop indefinitely; the cpu will
be stuck at this point.

The bug was exposed when VPHN was enabled in commit b7abef0 (v3.9).

Reported-by: Jan Stancek 
Signed-off-by: Robert Jennings 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc/numa: Do not update sysfs cpu registration from invalid context

2013-07-25T21:07:22+00:00

commit dd023217e17e72b46fb4d49c7734c426938c3dba upstream.

The topology update code that updates the cpu node registration in sysfs
should not be called while in stop_machine(). The register/unregister
calls take a lock and may sleep.

This patch moves these calls outside of the call to stop_machine().

Signed-off-by: Nathan Fontenot 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc: Fix bad pmd error with book3E config

2013-06-20T05:25:21+00:00

Book3E uses the hugepd at PMD level and don't encode pte directly
at the pmd level. So it will find the lower bits of pmd set
and the pmd_bad check throws error. Infact the current code
will never take the free_hugepd_range call at all because it will
clear the pmd if it find a hugepd pointer. Fix this by clearing
bad pmd only if it is not a hugepd pointer.

This is regression introduced by e2b3d202d1dba8f3546ed28224ce485bc50010be
"powerpc: Switch 16GB and 16MB explicit hugepages to a different page table format"

Reported-by: Scott Wood 
Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Benjamin Herrenschmidt

powerpc/mm: Always invalidate tlb on hpte invalidate and update

2013-05-31T22:29:26+00:00

If a hash bucket gets full, we "evict" a more/less random entry from it.
When we do that we don't invalidate the TLB (hpte_remove) because we assume
the old translation is still technically "valid". This implies that when
we are invalidating or updating pte, even if HPTE entry is not valid
we should do a tlb invalidate.

This was a regression introduced by b1022fbd293564de91596b8775340cf41ad5214c

Signed-off-by: Aneesh Kumar K.V 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Exception hooks for context tracking subsystem

2013-05-14T06:00:19+00:00

This is the exception hooks for context tracking subsystem, including
data access, program check, single step, instruction breakpoint, machine check,
alignment, fp unavailable, altivec assist, unknown exception, whose handlers
might use RCU.

This patch corresponds to
[PATCH] x86: Exception hooks for userspace RCU extended QS
  commit 6ba3c97a38803883c2eee489505796cb0a727122

But after the exception handling moved to generic code, and some changes in
following two commits:
56dd9470d7c8734f055da2a6bac553caf4a468eb
  context_tracking: Move exception handling to generic code
6c1e0256fad84a843d915414e4b5973b7443d48d
  context_tracking: Restore correct previous context state on exception exit

it is able for exception hooks to use the generic code above instead of a
redundant arch implementation.

Signed-off-by: Li Zhong 
Signed-off-by: Benjamin Herrenschmidt