[PATCH v3] arm64: Enable perf events based hard lockup detector

[Will Deacon]

On Fri, Sep 04, 2020 at 12:56:37PM +0530, Sumit Garg wrote:
> With the recent feature added to enable perf events to use pseudo NMIs
> as interrupts on platforms which support GICv3 or later, its now been
> possible to enable hard lockup detector (or NMI watchdog) on arm64
> platforms. So enable corresponding support.
> 
> One thing to note here is that normally lockup detector is initialized
> just after the early initcalls but PMU on arm64 comes up much later as
> device_initcall(). So we need to re-initialize lockup detection once
> PMU has been initialized.
> 
> Signed-off-by: Sumit Garg <sumit.garg at linaro.org>
> ---
> 
> Changes in v3:
> - Rebased to latest pmu NMI patch-set [1].
> - Addressed misc. comments from Stephen.
> 
> [1] https://lkml.org/lkml/2020/8/19/671
> 
> Changes since RFC:
> - Rebased on top of Alex's WIP-pmu-nmi branch.
> - Add comment for safe max. CPU frequency.
> - Misc. cleanup.
> 
>  arch/arm64/Kconfig             |  2 ++
>  arch/arm64/kernel/perf_event.c | 41 +++++++++++++++++++++++++++++++++++++++--
>  drivers/perf/arm_pmu.c         |  9 +++++++++
>  include/linux/perf/arm_pmu.h   |  2 ++
>  4 files changed, 52 insertions(+), 2 deletions(-)

It would be great to have Alexandru's ack on this, since it builds directly
on top of his code.

Will