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Date: Fri, 2 Dec 2022 19:23:13 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>,
Yury Norov <yury.norov@...il.com>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Marc Zyngier <maz@...nel.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>,
Namhyung Kim <namhyung@...nel.org>,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Oliver Upton <oliver.upton@...ux.dev>,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org
Subject: Re: [PATCH 0/9] tools: Make {clear,set}_bit() atomic for reals
On 11/19/22 02:34, Sean Christopherson wrote:
> For obvious reasons I'd like to route the this through Paolo's tree.
> In theory, taking just patch 5 through tip would work, but creating a
> topic branch seems like the way to go, though maybe I'm being overly
> paranoid. The current tip/perf/core doesn't have any conflicts, nor does
> it have new set_bit() or clear_bit() users.
>
>
> Code sitting in kvm/queue for 6.2 adds functionality that relies on
> clear_bit() being an atomic operation. Unfortunately, despite being
> implemented in atomic.h (among other strong hits that they should be
> atomic), clear_bit() and set_bit() aren't actually atomic (and of course
> I realized this _just_ after everything got queued up).
>
> Move current tools/ users of clear_bit() and set_bit() to the
> double-underscore versions (which tools/ already provides and documents
> as being non-atomic), and then implement clear_bit() and set_bit() as
> actual atomics to fix the KVM selftests bug.
>
> Perf and KVM are the only affected users. NVDIMM also has test code
> in tools/, but that builds against the kernel proper. The KVM code is
> well tested and fully audited. The perf code is lightly tested; if I
> understand the build system, it's probably not even fully compile tested.
>
> Patches 1 and 2 are completely unrelated and are fixes for patches
> sitting in kvm/queue. Paolo, they can be squashed if you want to rewrite
> history.
>
> Patch 3 fixes a hilarious collision in a KVM ARM selftest that will arise
> when clear_bit() is converted to an atomic.
>
> Patch 4 changes clear_bit() and set_bit() to take an "unsigned long"
> instead of an "int" so that patches 5-6 aren't accompanied by functional
> changes. I.e. if something in perf is somehow relying on "bit" being a
> signed int, failures will bisect to patch 4 and not to the
> supposed-to-be-a-nop conversion to __clear_bit() and __set_bit().
>
> Patch 5-9 switch perf+KVM and complete the conversion.
>
> Applies on:
>
> git://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
Queued, thanks Namhyung for the ACK!
Paolo
>
> Sean Christopherson (9):
> KVM: selftests: Add rdmsr_from_l2() implementation in Hyper-V eVMCS
> test
> KVM: selftests: Remove unused "vcpu" param to fix build error
> KVM: arm64: selftests: Enable single-step without a "full" ucall()
> tools: Take @bit as an "unsigned long" in {clear,set}_bit() helpers
> perf tools: Use dedicated non-atomic clear/set bit helpers
> KVM: selftests: Use non-atomic clear/set bit helpers in KVM tests
> tools: Drop conflicting non-atomic test_and_{clear,set}_bit() helpers
> tools: Drop "atomic_" prefix from atomic test_and_set_bit()
> tools: KVM: selftests: Convert clear/set_bit() to actual atomics
>
> tools/arch/x86/include/asm/atomic.h | 6 +++-
> tools/include/asm-generic/atomic-gcc.h | 13 ++++++-
> tools/include/asm-generic/bitops/atomic.h | 15 ++++----
> tools/include/linux/bitmap.h | 34 -------------------
> tools/perf/bench/find-bit-bench.c | 2 +-
> tools/perf/builtin-c2c.c | 6 ++--
> tools/perf/builtin-kwork.c | 6 ++--
> tools/perf/builtin-record.c | 6 ++--
> tools/perf/builtin-sched.c | 2 +-
> tools/perf/tests/bitmap.c | 2 +-
> tools/perf/tests/mem2node.c | 2 +-
> tools/perf/util/affinity.c | 4 +--
> tools/perf/util/header.c | 8 ++---
> tools/perf/util/mmap.c | 6 ++--
> tools/perf/util/pmu.c | 2 +-
> .../util/scripting-engines/trace-event-perl.c | 2 +-
> .../scripting-engines/trace-event-python.c | 2 +-
> tools/perf/util/session.c | 2 +-
> tools/perf/util/svghelper.c | 2 +-
> .../selftests/kvm/aarch64/arch_timer.c | 2 +-
> .../selftests/kvm/aarch64/debug-exceptions.c | 21 ++++++------
> tools/testing/selftests/kvm/dirty_log_test.c | 34 +++++++++----------
> .../selftests/kvm/include/ucall_common.h | 8 +++++
> .../testing/selftests/kvm/lib/ucall_common.c | 2 +-
> .../selftests/kvm/x86_64/hyperv_evmcs.c | 13 +++++--
> .../selftests/kvm/x86_64/hyperv_svm_test.c | 4 +--
> .../selftests/kvm/x86_64/hyperv_tlb_flush.c | 2 +-
> 27 files changed, 102 insertions(+), 106 deletions(-)
>
>
> base-commit: 3321eef4acb51c303f0598d8a8493ca58528a054
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