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Overriding the idle mechanism might be useful for debugging and performance
testing. Add a cmdline parameter for it, similar to the existing idle=
parameter already present for the x86 and ppc architectures.
It is also useful on platforms where the WFI instruction misbehaves,
such as Apple Silicon SoCs. Generally, a misbehaving instruction should
be treated as an erratum and patched using the alternatives framework.
However, in the Apple Silicon case we need more flexibility because it is
difficult to detect whether the erratum applies. For example, Linux VMs
inside macOS have the same MIDR and may even seem like they're running
in EL2 in the case of NV, but should continue using WFI (it's trapped and
handled correctly by the hypervisor there). Thus, we prefer to
let the m1n1 bootloader add the idle=nop parameter[1].
Link[1]: https://lore.kernel.org/all/99b69262-e54b-424e-baa2-96ef7013b87a@kernel.org/
Suggested-by: Will Deacon <will@kernel.org>
Signed-off-by: Yureka Lilian <yureka@cyberchaos.dev>
Signed-off-by: Will Deacon <will@kernel.org>
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As per the (somewhat recent) comment before the definition of
`__cpuidle`, the tag is like `noinstr` but also marks a function so it
can be identified by cpu_in_idle(). Let's add these markings to arm64
cpuidle functions
With this change we get useful backtraces like:
NMI backtrace for cpu N skipped: idling at cpu_do_idle+0x94/0x98
instead of useless backtraces when dumping all processors using
nmi_cpu_backtrace().
NOTE: this patch won't make cpu_in_idle() work perfectly for arm64,
but it doesn't hurt and does catch some cases. Specifically an example
that wasn't caught in my testing looked like this:
gic_cpu_sys_reg_init+0x1f8/0x314
gic_cpu_pm_notifier+0x40/0x78
raw_notifier_call_chain+0x5c/0x134
cpu_pm_notify+0x38/0x64
cpu_pm_exit+0x20/0x2c
psci_enter_idle_state+0x48/0x70
cpuidle_enter_state+0xb8/0x260
cpuidle_enter+0x44/0x5c
do_idle+0x188/0x30c
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Acked-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20230906090246.v13.2.I4baba13e220bdd24d11400c67f137c35f07f82c7@changeid
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Current arch_cpu_idle() is called with IRQs disabled, but will return
with IRQs enabled.
However, the very first thing the generic code does after calling
arch_cpu_idle() is raw_local_irq_disable(). This means that
architectures that can idle with IRQs disabled end up doing a
pointless 'enable-disable' dance.
Therefore, push this IRQ disabling into the idle function, meaning
that those architectures can avoid the pointless IRQ state flipping.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Acked-by: Mark Rutland <mark.rutland@arm.com> [arm64]
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Guo Ren <guoren@kernel.org>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195540.618076436@infradead.org
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The never-ending entry.S refactoring continues, putting us in a much
better place wrt compiler instrumentation whilst moving more of the code
into C.
* for-next/entry:
arm64: idle: don't instrument idle code with KCOV
arm64: entry: don't instrument entry code with KCOV
arm64: entry: make NMI entry/exit functions static
arm64: entry: split SDEI entry
arm64: entry: split bad stack entry
arm64: entry: fold el1_inv() into el1h_64_sync_handler()
arm64: entry: handle all vectors with C
arm64: entry: template the entry asm functions
arm64: entry: improve bad_mode()
arm64: entry: move bad_mode() to entry-common.c
arm64: entry: consolidate EL1 exception returns
arm64: entry: organise entry vectors consistently
arm64: entry: organise entry handlers consistently
arm64: entry: convert IRQ+FIQ handlers to C
arm64: entry: add a call_on_irq_stack helper
arm64: entry: move NMI preempt logic to C
arm64: entry: move arm64_preempt_schedule_irq to entry-common.c
arm64: entry: convert SError handlers to C
arm64: entry: unmask IRQ+FIQ after EL0 handling
arm64: remove redundant local_daif_mask() in bad_mode()
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The low-level idle code in arch_cpu_idle() and its callees runs at a
time where where portions of the kernel environment aren't available.
For example, RCU may not be watching, and lockdep state may be
out-of-sync with the hardware. Due to this, it is not sound to
instrument this code.
We generally avoid instrumentation by marking the entry functions as
`noinstr`, but currently this doesn't inhibit KCOV instrumentation.
Prevent this by factoring these functions into a new idle.c so that we
can disable KCOV for the entire compilation unit, as is done for the
core idle code in kernel/sched/idle.c.
We'd like to keep instrumentation of the rest of process.c, and for the
existing code in cpuidle.c, so a new compilation unit is preferable. The
arch_cpu_idle_dead() function in process.c is a cpu hotplug function
that is safe to instrument, so it is left as-is in process.c.
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210607094624.34689-21-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
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