linux-stable.git/tools/arch/arm64/include, branch v5.5

tools headers kvm: Sync kvm headers with the kernel sources

2019-12-02T15:54:13+00:00

To pick up the changes from:

  14edff88315a Merge tag 'kvmarm-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD
  a4b28f5c6798 Merge remote-tracking branch 'kvmarm/kvm-arm64/stolen-time' into kvmarm-master/next
  58772e9a3db7 ("KVM: arm64: Provide VCPU attributes for stolen time")
  da345174ceca ("KVM: arm/arm64: Allow user injection of external data aborts")
  c726200dd106 ("KVM: arm/arm64: Allow reporting non-ISV data aborts to userspace")
  efe5ddcae496 ("KVM: PPC: Book3S HV: XIVE: Allow userspace to set the # of VPs")

No tools changes are caused by this, as the only defines so far used
from these files are for syscall arg pretty printing are:

  $ grep KVM tools/perf/trace/beauty/*.sh
  tools/perf/trace/beauty/kvm_ioctl.sh:regex='^#[[:space:]]*define[[:space:]]+KVM_(\w+)[[:space:]]+_IO[RW]*\([[:space:]]*KVMIO[[:space:]]*,[[:space:]]*(0x[[:xdigit:]]+).*'
  $

Some are also include by:

  tools/perf/arch/x86/util/kvm-stat.c
  tools/perf/arch/powerpc/util/kvm-stat.c

This addresses these tools/perf build warnings:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/kvm.h' differs from latest version at 'include/uapi/linux/kvm.h'
  diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h
  Warning: Kernel ABI header at 'tools/arch/powerpc/include/uapi/asm/kvm.h' differs from latest version at 'arch/powerpc/include/uapi/asm/kvm.h'
  diff -u tools/arch/powerpc/include/uapi/asm/kvm.h arch/powerpc/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm/include/uapi/asm/kvm.h arch/arm/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm64/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm64/include/uapi/asm/kvm.h arch/arm64/include/uapi/asm/kvm.h

Cc: Adrian Hunter 
Cc: Christoffer Dall 
Cc: Fabiano Rosas 
Cc: Greg Kurz 
Cc: Jiri Olsa 
Cc: Marc Zyngier 
Cc: Namhyung Kim 
Cc: Paul Mackerras 
Cc: Steven Price 
Link: https://lkml.kernel.org/n/tip-qrjdudhq25mk5bfnhveofbm4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools headers kvm: Sync kvm headers with the kernel sources

2019-09-30T20:29:30+00:00

To pick the changes in:

  200824f55eef ("KVM: s390: Disallow invalid bits in kvm_valid_regs and kvm_dirty_regs")
  4a53d99dd0c2 ("KVM: VMX: Introduce exit reason for receiving INIT signal on guest-mode")
  7396d337cfad ("KVM: x86: Return to userspace with internal error on unexpected exit reason")
  92f35b751c71 ("KVM: arm/arm64: vgic: Allow more than 256 vcpus for KVM_IRQ_LINE")

None of them trigger any changes in tooling, this time this is just to silence
these perf build warnings:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/kvm.h' differs from latest version at 'include/uapi/linux/kvm.h'
  diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h
  Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/vmx.h' differs from latest version at 'arch/x86/include/uapi/asm/vmx.h'
  diff -u tools/arch/x86/include/uapi/asm/vmx.h arch/x86/include/uapi/asm/vmx.h
  Warning: Kernel ABI header at 'tools/arch/s390/include/uapi/asm/kvm.h' differs from latest version at 'arch/s390/include/uapi/asm/kvm.h'
  diff -u tools/arch/s390/include/uapi/asm/kvm.h arch/s390/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm/include/uapi/asm/kvm.h arch/arm/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm64/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm64/include/uapi/asm/kvm.h arch/arm64/include/uapi/asm/kvm.h

Cc: Adrian Hunter 
Cc: Janosch Frank 
Cc: Jiri Olsa 
Cc: Liran Alon 
Cc: Marc Zyngier 
Cc: Namhyung Kim 
Cc: Paolo Bonzini 
Cc: Thomas Huth 
Link: https://lkml.kernel.org/n/tip-akuugvvjxte26kzv23zp5d2z@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools headers UAPI: Update tools's copy of kvm.h headers

2019-07-26T15:43:23+00:00

Picking the changes from:

  66bb8a065f5a ("KVM: x86: PMU Event Filter")
  f087a02941fe ("KVM: nVMX: Stash L1's CR3 in vmcs01.GUEST_CR3 on nested entry w/o EPT")
  99adb567632b ("KVM: arm/arm64: Add save/restore support for firmware workaround state")

Silencing this perf build warning:

  Warning: Kernel ABI header at 'tools/arch/arm/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm/include/uapi/asm/kvm.h arch/arm/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm64/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm64/include/uapi/asm/kvm.h arch/arm64/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/vmx.h' differs from latest version at 'arch/x86/include/uapi/asm/vmx.h'
  diff -u tools/arch/x86/include/uapi/asm/vmx.h arch/x86/include/uapi/asm/vmx.h
  Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/kvm.h' differs from latest version at 'arch/x86/include/uapi/asm/kvm.h'
  diff -u tools/arch/x86/include/uapi/asm/kvm.h arch/x86/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/include/uapi/linux/kvm.h' differs from latest version at 'include/uapi/linux/kvm.h'
  diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h

Now 'perf trace' and other code that might use the tools/perf/trace/beauty autogenerated
tables will be able to translate this new ioctl code into a string:

  $ tools/perf/trace/beauty/kvm_ioctl.sh > before
  $
  $ cp include/uapi/linux/kvm.h tools/include/uapi/linux/kvm.h
  $ tools/perf/trace/beauty/kvm_ioctl.sh > after
  $ diff -u before after
  --- before 2019-07-26 12:32:47.959220236 -0300
  +++ after 2019-07-26 12:33:05.766464871 -0300
  @@ -79,6 +79,7 @@
        [0xac] = "SET_ONE_REG",
        [0xad] = "KVMCLOCK_CTRL",
        [0xb0] = "GET_REG_LIST",
  +     [0xb2] = "SET_PMU_EVENT_FILTER",
        [0xb7] = "SMI",
        [0xba] = "MEMORY_ENCRYPT_OP",
        [0xbb] = "MEMORY_ENCRYPT_REG_REGION",
  $

Cc: Adrian Hunter 
Cc: Andre Przywara 
Cc: Brendan Gregg 
Cc: Eric Hankland 
Cc: Jiri Olsa 
Cc: Luis Cláudio Gonçalves 
Cc: Marc Zyngier 
Cc: Namhyung Kim 
Cc: Paolo Bonzini 
Cc: Sean Christopherson 
Link: https://lkml.kernel.org/n/tip-py1gcmt6rboehlwg6zvagfg2@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools arch kvm: Sync kvm headers with the kernel sources

2019-07-06T17:26:40+00:00

To pick up the changes from:

  41040cf7c5f0 ("arm64/sve: Fix missing SVE/FPSIMD endianness conversions")
  6ca00dfafda7 ("KVM: x86: Modify struct kvm_nested_state to have explicit fields for data")

None entail changes in tooling.

This silences these tools/perf build warnings:

  Warning: Kernel ABI header at 'tools/arch/x86/include/uapi/asm/kvm.h' differs from latest version at 'arch/x86/include/uapi/asm/kvm.h'
  diff -u tools/arch/x86/include/uapi/asm/kvm.h arch/x86/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm64/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm64/include/uapi/asm/kvm.h arch/arm64/include/uapi/asm/kvm.h

Cc: Adrian Hunter 
Cc: Dave Martin 
Cc: Jiri Olsa 
Cc: Liran Alon 
Cc: Namhyung Kim 
Cc: Paolo Bonzini 
Cc: Will Deacon 
Link: https://lkml.kernel.org/n/tip-1cdbq5ulr4d6cx3iv2ye5wdv@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools headers UAPI: Sync kvm.h headers with the kernel sources

2019-05-28T12:52:23+00:00

  dd53f6102c30 ("Merge tag 'kvmarm-for-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into HEAD")
  59c5c58c5b93 ("Merge tag 'kvm-ppc-next-5.2-2' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc into HEAD")
  d7547c55cbe7 ("KVM: Introduce KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2")
  6520ca64cde7 ("KVM: PPC: Book3S HV: XIVE: Add a mapping for the source ESB pages")
  39e9af3de5ca ("KVM: PPC: Book3S HV: XIVE: Add a TIMA mapping")
  e4945b9da52b ("KVM: PPC: Book3S HV: XIVE: Add get/set accessors for the VP XIVE state")
  e6714bd1671d ("KVM: PPC: Book3S HV: XIVE: Add a control to dirty the XIVE EQ pages")
  7b46b6169ab8 ("KVM: PPC: Book3S HV: XIVE: Add a control to sync the sources")
  5ca806474859 ("KVM: PPC: Book3S HV: XIVE: Add a global reset control")
  13ce3297c576 ("KVM: PPC: Book3S HV: XIVE: Add controls for the EQ configuration")
  e8676ce50e22 ("KVM: PPC: Book3S HV: XIVE: Add a control to configure a source")
  4131f83c3d64 ("KVM: PPC: Book3S HV: XIVE: add a control to initialize a source")
  eacc56bb9de3 ("KVM: PPC: Book3S HV: XIVE: Introduce a new capability KVM_CAP_PPC_IRQ_XIVE")
  90c73795afa2 ("KVM: PPC: Book3S HV: Add a new KVM device for the XIVE native exploitation mode")
  4f45b90e1c03 ("KVM: s390: add deflate conversion facilty to cpu model")
  a243c16d18be ("KVM: arm64: Add capability to advertise ptrauth for guest")
  a22fa321d13b ("KVM: arm64: Add userspace flag to enable pointer authentication")
  4bd774e57b29 ("KVM: arm64/sve: Simplify KVM_REG_ARM64_SVE_VLS array sizing")
  8ae6efdde451 ("KVM: arm64/sve: Clean up UAPI register ID definitions")
  173aec2d5a9f ("KVM: s390: add enhanced sort facilty to cpu model")
  555f3d03e7fb ("KVM: arm64: Add a capability to advertise SVE support")
  9033bba4b535 ("KVM: arm64/sve: Add pseudo-register for the guest's vector lengths")
  7dd32a0d0103 ("KVM: arm/arm64: Add KVM_ARM_VCPU_FINALIZE ioctl")
  e1c9c98345b3 ("KVM: arm64/sve: Add SVE support to register access ioctl interface")
  2b953ea34812 ("KVM: Allow 2048-bit register access via ioctl interface")

None entails changes in tooling, the closest to that were some new arch
specific ioctls, that are still not handled by the tools/perf/trace/beauty/
library, that needs to create per-arch tables to convert ioctl cmd->string (and
back).

From a quick look the arch specific kvm-stat.c files at:

  $ ls -1 tools/perf/arch/*/util/kvm-stat.c
  tools/perf/arch/powerpc/util/kvm-stat.c
  tools/perf/arch/s390/util/kvm-stat.c
  tools/perf/arch/x86/util/kvm-stat.c
  $

Are not affected.

This silences these perf building warnings:

  Warning: Kernel ABI header at 'tools/include/uapi/linux/kvm.h' differs from latest version at 'include/uapi/linux/kvm.h'
  diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h
  Warning: Kernel ABI header at 'tools/arch/powerpc/include/uapi/asm/kvm.h' differs from latest version at 'arch/powerpc/include/uapi/asm/kvm.h'
  diff -u tools/arch/powerpc/include/uapi/asm/kvm.h arch/powerpc/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/s390/include/uapi/asm/kvm.h' differs from latest version at 'arch/s390/include/uapi/asm/kvm.h'
  diff -u tools/arch/s390/include/uapi/asm/kvm.h arch/s390/include/uapi/asm/kvm.h
  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/kvm.h' differs from latest version at 'arch/arm64/include/uapi/asm/kvm.h'
  diff -u tools/arch/arm64/include/uapi/asm/kvm.h arch/arm64/include/uapi/asm/kvm.h

Cc: Adrian Hunter 
Cc: Amit Daniel Kachhap 
Cc: Brendan Gregg 
Cc: Cédric Le Goater 
Cc: Christian Borntraeger 
Cc: Dave Martin 
Cc: Jiri Olsa 
Cc: Luis Cláudio Gonçalves 
Cc: Marc Zyngier 
Cc: Namhyung Kim 
Cc: Paolo Bonzini 
Cc: Paul Mackerras 
Cc: Peter Xu 
Link: https://lkml.kernel.org/n/tip-3msmqjenlmb7eygcdnmlqaq1@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools: add smp_* barrier variants to include infrastructure

2019-04-11T21:45:50+00:00

Add the definition for smp_rmb(), smp_wmb(), and smp_mb() to the
tools include infrastructure: this patch adds the implementation
for x86-64 and arm64, and have it fall back as currently is for
other archs which do not have it implemented at this point. The
x86-64 one uses lock + add combination for smp_mb() with address
below red zone.

This is on top of 09d62154f613 ("tools, perf: add and use optimized
ring_buffer_{read_head, write_tail} helpers"), which didn't touch
smp_* barrier implementations. Magnus recently rightfully reported
however that the latter on x86-64 still wrongly falls back to sfence,
lfence and mfence respectively, thus fix that for applications under
tools making use of these to avoid such ugly surprises. The main
header under tools (include/asm/barrier.h) will in that case not
select the fallback implementation.

Reported-by: Magnus Karlsson 
Signed-off-by: Daniel Borkmann 
Cc: Arnaldo Carvalho de Melo 
Signed-off-by: Alexei Starovoitov

tools headers uapi: Sync copy of asm-generic/unistd.h with the kernel sources

2019-03-11T19:13:04+00:00

To get the changes in:

  c8ce48f06503 ("asm-generic: Make time32 syscall numbers optional")

Silencing these tools/perf build warnings:

  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/unistd.h' differs from latest version at 'arch/arm64/include/uapi/asm/unistd.h'
  diff -u tools/arch/arm64/include/uapi/asm/unistd.h arch/arm64/include/uapi/asm/unistd.h
  Warning: Kernel ABI header at 'tools/include/uapi/asm-generic/unistd.h' differs from latest version at 'include/uapi/asm-generic/unistd.h'
  diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h

Test built it under the ubuntu:14.04.4-x-linaro-arm64 cross build
environment and looked at the syscall table at
/tmp/build/perf/arch/arm64/include/generated/asm/syscalls.c, looks ok.

Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Arnd Bergmann 
Cc: Hendrik Brueckner 
Cc: Jiri Olsa 
Cc: Kim Phillips 
Cc: Michael Ellerman 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Cc: Ravi Bangoria 
Cc: Thomas Richter 
Link: https://lkml.kernel.org/n/tip-e4w7ngsmkq48bd6st52ty2kb@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools headers barrier: Fix arm64 tools build failure wrt smp_load_{acquire,release}

2018-11-01T13:07:43+00:00

Cheers for reporting this. I managed to reproduce the build failure with
gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1).

The code in question is the arm64 versions of smp_load_acquire() and
smp_store_release(). Unlike other architectures, these are not built
around READ_ONCE() and WRITE_ONCE() since we have instructions we can
use instead of fences. Bringing our macros up-to-date with those (i.e.
tweaking the union initialisation and using the special "uXX_alias_t"
types) appears to fix the issue for me.

Committer notes:

Testing it in the systems previously failing:

  # time dm android-ndk:r12b-arm \
         android-ndk:r15c-arm \
         debian:experimental-x-arm64 \
         ubuntu:14.04.4-x-linaro-arm64 \
         ubuntu:16.04-x-arm \
         ubuntu:16.04-x-arm64 \
         ubuntu:18.04-x-arm \
         ubuntu:18.04-x-arm64
    1 android-ndk:r12b-arm          : Ok   arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
    2 android-ndk:r15c-arm          : Ok   arm-linux-androideabi-gcc (GCC) 4.9.x 20150123 (prerelease)
    3 debian:experimental-x-arm64   : Ok   aarch64-linux-gnu-gcc (Debian 8.2.0-7) 8.2.0
    4 ubuntu:14.04.4-x-linaro-arm64 : Ok   aarch64-linux-gnu-gcc (Linaro GCC 5.5-2017.10) 5.5.0
    5 ubuntu:16.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
    6 ubuntu:16.04-x-arm64          : Ok   aarch64-linux-gnu-gcc (Ubuntu/Linaro 5.4.0-6ubuntu1~16.04.9) 5.4.0 20160609
    7 ubuntu:18.04-x-arm            : Ok   arm-linux-gnueabihf-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0
    8 ubuntu:18.04-x-arm64          : Ok   aarch64-linux-gnu-gcc (Ubuntu/Linaro 7.3.0-27ubuntu1~18.04) 7.3.0

Reported-by: Arnaldo Carvalho de Melo 
Signed-off-by: Will Deacon 
Tested-by: Arnaldo Carvalho de Melo 
Tested-by: Daniel Borkmann 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20181031174408.GA27871@arm.com
Signed-off-by: Arnaldo Carvalho de Melo

tools arch uapi: Update asm-generic/unistd.h and arm64 unistd.h copies

2018-10-31T12:57:51+00:00

To get the changes in:

  82b355d161c9 ("y2038: Remove newstat family from default syscall set")

Which will make the syscall table used by 'perf trace' for arm64 to be
updated from the changes in that patch.

This silences these perf build warnings:

  Warning: Kernel ABI header at 'tools/arch/arm64/include/uapi/asm/unistd.h' differs from latest version at 'arch/arm64/include/uapi/asm/unistd.h'
  diff -u tools/arch/arm64/include/uapi/asm/unistd.h arch/arm64/include/uapi/asm/unistd.h
  Warning: Kernel ABI header at 'tools/include/uapi/asm-generic/unistd.h' differs from latest version at 'include/uapi/asm-generic/unistd.h'
  diff -u tools/include/uapi/asm-generic/unistd.h include/uapi/asm-generic/unistd.h

Cc: Kim Phillips 
Cc: Arnd Bergmann 
Cc: Geert Uytterhoeven 
Cc: Jiri Olsa 
Cc: Namhyung Kim 
Link: https://lkml.kernel.org/n/tip-3euy7c4yy5mvnp5bm16t9vqg@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo

tools, perf: add and use optimized ring_buffer_{read_head, write_tail} helpers

2018-10-19T20:43:08+00:00

Currently, on x86-64, perf uses LFENCE and MFENCE (rmb() and mb(),
respectively) when processing events from the perf ring buffer which
is unnecessarily expensive as we can do more lightweight in particular
given this is critical fast-path in perf.

According to Peter rmb()/mb() were added back then via a94d342b9cb0
("tools/perf: Add required memory barriers") at a time where kernel
still supported chips that needed it, but nowadays support for these
has been ditched completely, therefore we can fix them up as well.

While for x86-64, replacing rmb() and mb() with smp_*() variants would
result in just a compiler barrier for the former and LOCK + ADD for
the latter (__sync_synchronize() uses slower MFENCE by the way), Peter
suggested we can use smp_{load_acquire,store_release}() instead for
architectures where its implementation doesn't resolve in slower smp_mb().
Thus, e.g. in x86-64 we would be able to avoid CPU barrier entirely due
to TSO. For architectures where the latter needs to use smp_mb() e.g.
on arm, we stick to cheaper smp_rmb() variant for fetching the head.

This work adds helpers ring_buffer_read_head() and ring_buffer_write_tail()
for tools infrastructure that either switches to smp_load_acquire() for
architectures where it is cheaper or uses READ_ONCE() + smp_rmb() barrier
for those where it's not in order to fetch the data_head from the perf
control page, and it uses smp_store_release() to write the data_tail.
Latter is smp_mb() + WRITE_ONCE() combination or a cheaper variant if
architecture allows for it. Those that rely on smp_rmb() and smp_mb() can
further improve performance in a follow up step by implementing the two
under tools/arch/*/include/asm/barrier.h such that they don't have to
fallback to rmb() and mb() in tools/include/asm/barrier.h.

Switch perf to use ring_buffer_read_head() and ring_buffer_write_tail()
so it can make use of the optimizations. Later, we convert libbpf as
well to use the same helpers.

Side note [0]: the topic has been raised of whether one could simply use
the C11 gcc builtins [1] for the smp_load_acquire() and smp_store_release()
instead:

  __atomic_load_n(ptr, __ATOMIC_ACQUIRE);
  __atomic_store_n(ptr, val, __ATOMIC_RELEASE);

Kernel and (presumably) tooling shipped along with the kernel has a
minimum requirement of being able to build with gcc-4.6 and the latter
does not have C11 builtins. While generally the C11 memory models don't
align with the kernel's, the C11 load-acquire and store-release alone
/could/ suffice, however. Issue is that this is implementation dependent
on how the load-acquire and store-release is done by the compiler and
the mapping of supported compilers must align to be compatible with the
kernel's implementation, and thus needs to be verified/tracked on a
case by case basis whether they match (unless an architecture uses them
also from kernel side). The implementations for smp_load_acquire() and
smp_store_release() in this patch have been adapted from the kernel side
ones to have a concrete and compatible mapping in place.

  [0] http://patchwork.ozlabs.org/patch/985422/
  [1] https://gcc.gnu.org/onlinedocs/gcc/_005f_005fatomic-Builtins.html

Signed-off-by: Daniel Borkmann 
Acked-by: Peter Zijlstra (Intel) 
Cc: "Paul E. McKenney" 
Cc: Will Deacon 
Cc: Arnaldo Carvalho de Melo 
Signed-off-by: Alexei Starovoitov