linux-kernel - [PATCH v3 00/18] clocksource/arch_timer: Errata workaround infrastructure rework

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Date:   Tue,  4 Apr 2017 18:18:08 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Will Deacon <will.deacon@....com>,
        Scott Wood <oss@...error.net>,
        Hanjun Guo <hanjun.guo@...aro.org>,
        Ding Tianhong <dingtianhong@...wei.com>,
        dann frazier <dann.frazier@...onical.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v3 00/18] clocksource/arch_timer: Errata workaround infrastructure rework

It has recently become obvious that a number of arm64 systems have
been blessed with a set of timers that are slightly less than perfect,
and require a bit of hand-holding. We already have a bunch of
errata-specific code to deal with this, but as we're adding more
potential detection methods (DT, ACPI, capability), things are getting
a bit out of hands.

Instead of adding more ad-hoc fixes to an already difficult code base,
let's give ourselves a bit of an infrastructure that can deal with
this and hide most of the uggliness behind semi-frendly accessors.

The series is roughly structured as such:

- A bunch of arm64 specific patches that allow the rest of the
  workaround infrastructure to be built upon (such as being able to
  trap userspace access to the virtual counter). These are now
  separate in order to allow the creation of a shared branch between
  the arm64 and clocksource trees.

- The following patches rework the existing workarounds, allowing
  errata to be matched using a given detection method (DT, ACPI or
  core specific)

- Another set of patches allowing a workaround to affect a subset of
  the CPUs, and not the whole system

- We then work around a Cortex-A73 erratum, whose counter can return a
  wrong value if read while crossing a 32bit boundary. Yup.

- Finally, we add some ACPI-specific workarounds for HiSilicon
  platforms that have the HISILICON_ERRATUM_161010101 defect.

Note that so far, we only deal with arm64. Once the infrastructure is
agreed upon, we can look at generalizing it (to some extent) to 32bit
ARM (typical use case would be a 32bit guest running on an affected
host).

This has been tested on an ls2085 platform (with the
"fsl,erratum-a008585" erratum) and a set of models configured to
simulate various configurations of affected/unaffected CPUs, both as
hosts and as KVM guests.

* From v2:
  - Dropped the "global capability" detection method, which was
    currently unused, simplifying the code a bit
  - Turned saved_cntkctl into a per-CPU variable, allowing a mix of
    affected/unaffected CPUs to retrieve their own configuration
    (new patch)
  - Fixed a bug that could leave cntvct_el0 untrapped if reset with
    the user access bit set
  - Added default clause to the match_id switch
  - Added Daniel's Acks on the relevant patches
  - Rebased on 4.11-rc5

* From v1:
  - Addressed Hanjun and Mark review comments
  - Moved arm64 specific patches to the beginning of the series,
    leaving the clocksource patches at the end, resulting in an extra
    patch.
  - Added RBs, TBs, and Acks.

Marc Zyngier (18):
  arm64: Allow checking of a CPU-local erratum
  arm64: Add CNTVCT_EL0 trap handler
  arm64: Define Cortex-A73 MIDR
  arm64: cpu_errata: Allow an erratum to be match for all revisions of a
    core
  arm64: cpu_errata: Add capability to advertise Cortex-A73 erratum
    858921
  arm64: arch_timer: Add infrastructure for multiple erratum detection
    methods
  arm64: arch_timer: Add erratum handler for CPU-specific capability
  arm64: arch_timer: Move arch_timer_reg_read/write around
  arm64: arch_timer: Get rid of erratum_workaround_set_sne
  arm64: arch_timer: Rework the set_next_event workarounds
  arm64: arch_timer: Make workaround methods optional
  arm64: arch_timer: Allows a CPU-specific erratum to only affect a
    subset of CPUs
  arm64: arch_timer: Move clocksource_counter and co around
  arm64: arch_timer: Save cntkctl_el1 as a per-cpu variable
  arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled
  arm64: arch_timer: Workaround for Cortex-A73 erratum 858921
  arm64: arch_timer: Allow erratum matching with ACPI OEM information
  arm64: arch_timer: Add HISILICON_ERRATUM_161010101 ACPI matching data

 Documentation/arm64/silicon-errata.txt |   1 +
 arch/arm64/include/asm/arch_timer.h    |  43 ++-
 arch/arm64/include/asm/cpucaps.h       |   3 +-
 arch/arm64/include/asm/cputype.h       |   2 +
 arch/arm64/include/asm/esr.h           |   2 +
 arch/arm64/kernel/cpu_errata.c         |  15 +
 arch/arm64/kernel/cpufeature.c         |  13 +-
 arch/arm64/kernel/traps.c              |  14 +
 drivers/clocksource/Kconfig            |  11 +
 drivers/clocksource/arm_arch_timer.c   | 535 +++++++++++++++++++++++----------
 10 files changed, 466 insertions(+), 173 deletions(-)

-- 
2.11.0