At the moment we run through the arm64_features capability list for
each CPU and set the capability if one of the CPU supports it. This
could be problematic in a heterogeneous system with differing capabilities.
Delay the CPU feature checks until all the enabled CPUs are up(i.e,
smp_cpus_done(), so that we can make better decisions based on the
overall system capability. Once we decide and advertise the capabilities
the alternatives can be applied. From this state, we cannot roll back
a feature to disabled based on the values from a new hotplugged CPU,
due to the runtime patching and other reasons. So, for all new CPUs,
we need to make sure that they have the established system capabilities.
Failing which, we bring the CPU down, preventing it from turning online.
Once the capabilities are decided, any new CPU booting up goes through
verification to ensure that it has all the enabled capabilities and also
invokes the respective enable() method on the CPU.

The CPU errata checks are not delayed and is still executed per-CPU
to detect the respective capabilities. If we ever come across a non-errata
capability that needs to be checked on each-CPU, we could introduce them via
a new capability table(or introduce a flag), which can be processed per CPU.

The next patch will make the feature checks use the system wide
safe value of a feature register.

NOTE: The enable() methods associated with the capability is scheduled
on all the CPUs (which is the only use case at the moment). If we need
a different type of 'enable()' which only needs to be run once on any CPU,
we should be able to handle that when needed.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
[catalin.marinas@arm.com: static variable and coding style fixes]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

check_cpu_capabilities runs through a given list of caps and
checks if the system has the cap, updates the system capability
bitmap and also runs any enable() methods associated with them.
All of this is not quite obvious from the name 'check'. This
patch splits the check_cpu_capabilities into two parts :

1) update_cpu_capabilities
 => Runs through the given list and updates the system
    wide capability map.
2) enable_cpu_capabilities
 => Runs through the given list and invokes enable() (if any)
    for the caps enabled on the system.

Cc: Andre Przywara <andre.przywara@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Suggested-by: Catalin Marinas <catalin.marinsa@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Make use of the system wide safe register to decide the support
for mixed endian.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Add an API for reading the safe CPUID value across the
system from the new infrastructure.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch consolidates the CPU Sanity check to the new infrastructure.

Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch adds an infrastructure to keep track of the CPU feature
registers on the system. For each register, the infrastructure keeps
track of the system wide safe value of the feature bits. Also, tracks
the which fields of a register should be matched strictly across all
the CPUs on the system for the SANITY check infrastructure.

The feature bits are classified into following 3 types depending on
the implication of the possible values. This information is used to
decide the safe value for a feature.

LOWER_SAFE  - The smaller value is safer
HIGHER_SAFE - The bigger value is safer
EXACT       - We can't decide between the two, so a predefined safe_value is used.

This infrastructure will be later used to make better decisions for:

 - Kernel features (e.g, KVM, Debug)
 - SANITY Check
 - CPU capability
 - ELF HWCAP
 - Exposing CPU Feature register to userspace.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
[catalin.marinas@arm.com: whitespace fix]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Introduce a helper to extract cpuid feature for any given
width.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch moves the /proc/cpuinfo handling code:

arch/arm64/kernel/{setup.c to cpuinfo.c}

No functional changes
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Move the mixed endian support detection code to cpufeature.c
from cpuinfo.c. This also moves the update_cpu_features()
used by mixed endian detection code, which will get more
functionality.

Also moves the ID register field shifts to asm/sysreg.h,
where all the useful definitions will end up in later patches.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch moves the CPU feature detection code from
 arch/arm64/kernel/{setup.c to cpufeature.c}

The plan is to consolidate all the CPU feature handling
in cpufeature.c.

Apart from changing pr_fmt from "alternatives" to "cpu features",
there are no functional changes.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

At the moment the boot CPU stores the cpuinfo long before the
PERCPU areas are initialised by the kernel. This could be problematic
as the non-boot CPU data structures might get copied with the data
from the boot CPU, giving us no chance to detect if a particular CPU
updated its cpuinfo. This patch delays the boot cpu store to
smp_prepare_boot_cpu().

Also kills the setup_processor() which no longer does meaningful
work.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Delay the ELF HWCAP initialisation until all the (enabled) CPUs are
up, i.e, smp_cpus_done(). This is in preparation for detecting the
common features across the CPUS and creating a consistent ELF HWCAP
for the system.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

At early boot, we print the CPU version/revision. On a heterogeneous
system, we could have different types of CPUs. Print the CPU info for
all active cpus. Also, the secondary CPUs prints the message only when
they turn online.

Also, remove the redundant 'revision' information which doesn't
make any sense without the 'variant' field.
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Tested-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Commit 21539939 (arm64: 36 bit VA) introduced 36-bit VA support for
the arm64 kernel when the 16KB page configuration is enabled. While this
is a valid hardware configuration, it's not something we want to
encourage since it reduces the memory (and I/O) range that the kernel
can access. Make this depend on EXPERT to avoid complaints of Linux not
mapping the whole RAM, especially on platforms following the ARM
recommended memory map.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Unlike perf callchain relying on walk_stackframe(), dump_backtrace()
has its own backtrace logic. A major difference between them is the
moment a symbol is recorded. Perf writes down a symbol *before*
calling unwind_frame(), but dump_backtrace() prints it out *after*
unwind_frame(). As a result, the last valid symbol cannot be hooked
in case of dump_backtrace(). This patch addresses the issue as
synchronising dump_backtrace() with perf callchain.

A simple test and its results are as follows:

- crash trigger

 $ sudo echo c > /proc/sysrq-trigger

- current status

 Call trace:
 [<fffffe00003dc738>] sysrq_handle_crash+0x24/0x30
 [<fffffe00003dd2ac>] __handle_sysrq+0x128/0x19c
 [<fffffe00003dd730>] write_sysrq_trigger+0x60/0x74
 [<fffffe0000249fc4>] proc_reg_write+0x84/0xc0
 [<fffffe00001f2638>] __vfs_write+0x44/0x104
 [<fffffe00001f2e60>] vfs_write+0x98/0x1a8
 [<fffffe00001f3730>] SyS_write+0x50/0xb0

- with this change

 Call trace:
 [<fffffe00003dc738>] sysrq_handle_crash+0x24/0x30
 [<fffffe00003dd2ac>] __handle_sysrq+0x128/0x19c
 [<fffffe00003dd730>] write_sysrq_trigger+0x60/0x74
 [<fffffe0000249fc4>] proc_reg_write+0x84/0xc0
 [<fffffe00001f2638>] __vfs_write+0x44/0x104
 [<fffffe00001f2e60>] vfs_write+0x98/0x1a8
 [<fffffe00001f3730>] SyS_write+0x50/0xb0
 [<fffffe00000939ec>] el0_svc_naked+0x20/0x28

Note that this patch does not cover a case where MMU is disabled. The
last stack frame of swapper, for example, has PC in a form of physical
address. Unfortunately, a simple conversion using phys_to_virt() cannot
cover all scenarios since PC is retrieved from LR - 4, not LR. It is
a big tradeoff to change both head.S and unwind_frame() for only a few
of symbols in *.S. Thus, this hunk does not take care of the case.

Cc: AKASHI Takahiro <takahiro.akashi@linaro.org>
Cc: James Morse <james.morse@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jungseok Lee <jungseoklee85@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Currently, if cpuidle is disabled or not supported, powertop reports
zero wakeups and zero events. This is due to the cpu_idle tracepoints
are missing.

This patch is to make cpu_idle tracepoints always available even if
cpuidle is disabled or not supported.
Signed-off-by: Jisheng Zhang <jszhang@marvell.com>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

36bit VA lets us use 2 level page tables while limiting the
available address space to 64GB.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Steve Capper <steve.capper@linaro.org>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch turns on the 16K page support in the kernel. We
support 48bit VA (4 level page tables) and 47bit VA (3 level
page tables).

With 16K we can map 128 entries using contiguous bit hint
at level 3 to map 2M using single TLB entry.

TODO: 16K supports 32 contiguous entries at level 2 to get us
1G(which is not yet supported by the infrastructure). That should
be a separate patch altogether.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Jeremy Linton <jeremy.linton@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Christoffer Dall <christoffer.dall@linaro.org>
Cc: Steve Capper <steve.capper@linaro.org>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch adds the page size to the arm64 kernel image header
so that one can infer the PAGESIZE used by the kernel. This will
be helpful to diagnose failures to boot the kernel with page size
not supported by the CPU.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Ensure that the selected page size is supported by the CPU(s). If it doesn't
park it.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Update the help text for ARM64_64K_PAGES to reflect the reality
about AArch32 support.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

We choose NR_FIX_BTMAPS such that each slot (NR_FIX_BTMAPS * PAGE_SIZE)
can address 256K.

Use division to derive NR_FIX_BTMAPS rather than defining it for each
page size.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

We use !CONFIG_ARM64_64K_PAGES for CONFIG_ARM64_4K_PAGES
(and vice versa) in code. It all worked well, so far since
we only had two options. Now, with the introduction of 16K,
these cases will break. This patch cleans up the code to
use the required CONFIG symbol expression without the assumption
that !64K => 4K (and vice versa)

Cc: Will Deacon <will.deacon@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

At the moment, we only support maximum of 3-level page table for
swapper. With 48bit VA, 64K has only 3 levels and 4K uses section
mapping. Add support for 4-level page table for swapper, needed
by 16K pages.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Now that we can calculate the number of levels required for
mapping a va width, reserve exact number of pages that would
be required to cover the idmap. The idmap should be able to handle
the maximum physical address size supported.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Introduce helpers for finding the number of page table
levels required for a given VA width, shift for a particular
page table level.

Convert the existing users to the new helpers. More users
to follow.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

We use section maps with 4K page size to create the swapper/idmaps.
So far we have used !64K or 4K checks to handle the case where we
use the section maps.
This patch adds a new symbol, ARM64_SWAPPER_USES_SECTION_MAPS, to
handle cases where we use section maps, instead of using the page size
symbols.

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Move the kernel pagetable (both swapper and idmap) definitions
from the generic asm/page.h to a new file, asm/kernel-pgtable.h.

This is mostly a cosmetic change, to clean up the asm/page.h to
get rid of the arch specific details which are not needed by the
generic code.

Also renames the symbols to prevent conflicts. e.g,
 	BLOCK_SHIFT => SWAPPER_BLOCK_SHIFT

Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Fix handers to handlers.
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

ARMv7 does not have a PC alignment exception. ARMv8 AArch32
user space however can produce a PC alignment exception. Add
handler so that we do not dump an unexpected stack trace in
the logs.
Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

These were introduced by commit 03875ad5 (arm64: add
kc_offset_to_vaddr and kc_vaddr_to_offset macro).
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This reverts commit 1b6d7f87.

This patch would conflict with Dan Williams' "tree-wide convert to
memremap()" series (ioremap_cache replaced by arch_memremap)
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch add kc_offset_to_vaddr() and kc_vaddr_to_offset(),
the default version doesn't work on arm64, because arm64 kernel address
is below the PAGE_OFFSET, like module address and vmemmap address are
all below PAGE_OFFSET address.
Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Add ioremap_cache macro, because some code will test if this macro
is defined or not, and will generate a generric version if not defined,
for example, memremap.c do like this.
Signed-off-by: yalin wang <yalin.wang2010@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Sparse reports some new issues introduced by the kasan patches:

  arch/arm64/mm/kasan_init.c:91:13: warning: no previous prototype for
  'kasan_early_init' [-Wmissing-prototypes] void __init kasan_early_init(void)
             ^
  arch/arm64/mm/kasan_init.c:91:13: warning: symbol 'kasan_early_init'
  was not declared. Should it be static? [sparse]

This patch resolves the problem by adding a prototype for
kasan_early_init and marking the function as asmlinkage, since it's only
called from head.S.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This prints out the virtual memory assigned to KASan in the
boot crawl along with other memory assignments, if and only
if KASan is activated.

Example dmesg from the Juno Development board:

Memory: 1691156K/2080768K available (5465K kernel code, 444K rwdata,
2160K rodata, 340K init, 217K bss, 373228K reserved, 16384K cma-reserved)
Virtual kernel memory layout:
    kasan   : 0xffffff8000000000 - 0xffffff9000000000   (    64 GB)
    vmalloc : 0xffffff9000000000 - 0xffffffbdbfff0000   (   182 GB)
    vmemmap : 0xffffffbdc0000000 - 0xffffffbfc0000000   (     8 GB maximum)
              0xffffffbdc2000000 - 0xffffffbdc3fc0000   (    31 MB actual)
    fixed   : 0xffffffbffabfd000 - 0xffffffbffac00000   (    12 KB)
    PCI I/O : 0xffffffbffae00000 - 0xffffffbffbe00000   (    16 MB)
    modules : 0xffffffbffc000000 - 0xffffffc000000000   (    64 MB)
    memory  : 0xffffffc000000000 - 0xffffffc07f000000   (  2032 MB)
      .init : 0xffffffc0007f5000 - 0xffffffc00084a000   (   340 KB)
      .text : 0xffffffc000080000 - 0xffffffc0007f45b4   (  7634 KB)
      .data : 0xffffffc000850000 - 0xffffffc0008bf200   (   445 KB)
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This patch adds arch specific code for kernel address sanitizer
(see Documentation/kasan.txt).

1/8 of kernel addresses reserved for shadow memory. There was no
big enough hole for this, so virtual addresses for shadow were
stolen from vmalloc area.

At early boot stage the whole shadow region populated with just
one physical page (kasan_zero_page). Later, this page reused
as readonly zero shadow for some memory that KASan currently
don't track (vmalloc).
After mapping the physical memory, pages for shadow memory are
allocated and mapped.

Functions like memset/memmove/memcpy do a lot of memory accesses.
If bad pointer passed to one of these function it is important
to catch this. Compiler's instrumentation cannot do this since
these functions are written in assembly.
KASan replaces memory functions with manually instrumented variants.
Original functions declared as weak symbols so strong definitions
in mm/kasan/kasan.c could replace them. Original functions have aliases
with '__' prefix in name, so we could call non-instrumented variant
if needed.
Some files built without kasan instrumentation (e.g. mm/slub.c).
Original mem* function replaced (via #define) with prefixed variants
to disable memory access checks for such files.
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

This will be used by KASAN latter.
Signed-off-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

Commit 654672d4 ("locking/atomics: Add _{acquire|release|relaxed}()
variants of some atomic operation") introduced a relaxed atomic API to
Linux that maps nicely onto the arm64 memory model, including the new
ARMv8.1 atomic instructions.

This patch hooks up the API to our relaxed atomic instructions, rather
than have them all expand to the full-barrier variants as they do
currently.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>