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arm64: smp: Remove dedicated wakeup IPI

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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 <mark.rutland@arm.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230906090246.v13.3.I7209db47ef8ec151d3de61f59005bbc59fe8f113@changeid
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Mark Rutland 2023-09-06 09:02:58 -07:00 committed by Catalin Marinas
parent d0c14a7d36
commit 2b2d0a7a96
3 changed files with 14 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/arm64/include/asm/smp.h
View File

@ -89,9 +89,9 @@ extern void arch_send_call_function_single_ipi(int cpu);
extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
extern void arch_send_wakeup_ipi_mask(const struct cpumask *mask);
extern void arch_send_wakeup_ipi(unsigned int cpu);
#else
static inline void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
static inline void arch_send_wakeup_ipi(unsigned int cpu)
{
BUILD_BUG();
}

2
arch/arm64/kernel/acpi_parking_protocol.c
View File

@ -103,7 +103,7 @@ static int acpi_parking_protocol_cpu_boot(unsigned int cpu)
&mailbox->entry_point);
writel_relaxed(cpu_entry->gic_cpu_id, &mailbox->cpu_id);
arch_send_wakeup_ipi_mask(cpumask_of(cpu));
arch_send_wakeup_ipi(cpu);
return 0;
}

28
arch/arm64/kernel/smp.c
View File

@ -72,7 +72,6 @@ enum ipi_msg_type {
IPI_CPU_CRASH_STOP,
IPI_TIMER,
IPI_IRQ_WORK,
IPI_WAKEUP,
NR_IPI
};
@ -764,7 +763,6 @@ static const char *ipi_types[NR_IPI] __tracepoint_string = {
[IPI_CPU_CRASH_STOP] = "CPU stop (for crash dump) interrupts",
[IPI_TIMER] = "Timer broadcast interrupts",
[IPI_IRQ_WORK] = "IRQ work interrupts",
[IPI_WAKEUP] = "CPU wake-up interrupts",
};
static void smp_cross_call(const struct cpumask *target, unsigned int ipinr);
@ -797,13 +795,6 @@ void arch_send_call_function_single_ipi(int cpu)
smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC);
}
#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
{
smp_cross_call(mask, IPI_WAKEUP);
}
#endif
#ifdef CONFIG_IRQ_WORK
void arch_irq_work_raise(void)
{
@ -897,14 +888,6 @@ static void do_handle_IPI(int ipinr)
break;
#endif
#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
case IPI_WAKEUP:
WARN_ONCE(!acpi_parking_protocol_valid(cpu),
"CPU%u: Wake-up IPI outside the ACPI parking protocol\n",
cpu);
break;
#endif
default:
pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
break;
@ -979,6 +962,17 @@ void arch_smp_send_reschedule(int cpu)
smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}
#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
void arch_send_wakeup_ipi(unsigned int cpu)
{
/*
* We use a scheduler IPI to wake the CPU as this avoids the need for a
* dedicated IPI and we can safely handle spurious scheduler IPIs.
*/
arch_smp_send_reschedule(cpu);
}
#endif
#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
void tick_broadcast(const struct cpumask *mask)
{