Quoting Douglas Anderson (2023-08-24 08:30:29)
> From: Mark Rutland <[email protected]>
>
> To enable NMI backtrace and KGDB's NMI cpu roundup, we need to free up
> at least one dedicated IPI.
>
> On arm64 the IPI_WAKEUP IPI is only used for the ACPI parking protocol,
> which itself is only used on some very early ARMv8 systems which
> couldn't implement PSCI.
>
> Remove the IPI_WAKEUP IPI, and rely on the IPI_RESCHEDULE IPI to wake
> CPUs from the parked state. This will cause a tiny amonut of redundant
> work to check the thread flags, but this is miniscule in relation to the
> cost of taking and handling the IPI in the first place. We can safely
> handle redundant IPI_RESCHEDULE IPIs, so there should be no functional
> impact as a result of this change.
>
> Signed-off-by: Mark Rutland <[email protected]>
> Signed-off-by: Douglas Anderson <[email protected]>
> Cc: Catalin Marinas <[email protected]>
> Cc: Marc Zyngier <[email protected]>
> Cc: Sumit Garg <[email protected]>
> Cc: Will Deacon <[email protected]>
> ---

Reviewed-by: Stephen Boyd <[email protected]>


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