From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Marc Zyngier <maz@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org,
Will Deacon <will@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Valentin Schneider <valentin.schneider@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Russell King <linux@armlinux.org.uk>,
kernel-team@android.com
Subject: Re: [PATCH 0/3] arm64: Fix cpuidle with pseudo-NMI enabled
Date: Thu, 10 Jun 2021 17:28:23 +0100 [thread overview]
Message-ID: <20210610162823.GA20025@lpieralisi> (raw)
In-Reply-To: <20210608172715.2396787-1-maz@kernel.org>
On Tue, Jun 08, 2021 at 06:27:12PM +0100, Marc Zyngier wrote:
> It appears that although cpu_do_idle() is correctly dealing with the
> PMR/DAIF duality, the PSCI cpu-suspend code has been left unaware of
> it.
>
> On a system that uses PSCI for idle (such as the Ampere Altra I have
> access to), the kernel dies as soon as it enters idle (interrupts are
> off at the GIC CPU interface level). Boo.
After investigating a bit I realised that this should depend on
ICC_CTLR_EL3.PMHE - if that's clear the PMR should not affect the
GICR->CPU IRQ forwarding (or WakeRequest signal generation when the
GICR_WAKER.ProcessorSleep==1).
IIUC if PMHE == 0, the PMR plays no role in wfi completion (and
WakeSignal generation for a CPU/GICR in quiescent state).
I assume on Ampere Altra PMHE == 1.
This changes almost nothing to the need for this patchset but
at least we clarify this behaviour.
Also, we should not be writing ICC_PMR_EL1 when
GICR_WAKER.ProcessorSleep == 1 (which may be set in
gic_cpu_pm_notifier()), this can hang the system.
I wonder whether this arm_cpuidle_{save,restore}_context() should
be moved into the gic_cpu_pm_notifier() itself - which would
solve also the PSCI suspend issue Sudeep raised - it would be
a bit ugly though (CPU PM notifiers are run in S2R and CPUidle
automatically and this would work for any S2R/CPUidle backend
other than PSCI even though that does not/will never exist on
arm64 ;-))
https://lore.kernel.org/linux-arm-kernel/20210608182044.ayqa6fbab4jyz7kp@bogus
I still believe this series is right - just raised these points
for discussion.
Thanks,
Lorenzo
> Instead of spreading more magic code around, I've elected to provide a
> pair of helpers (arm_cpuidle_{save,restore}_context()) which do the
> heavy lifting.
>
> With that in place, I can finally boot the above system with
> irqchip.gicv3_pseudo_nmi=1. I'd welcome feedback from people who may
> have experienced similar issues in the past (and on different
> machines).
>
> Marc Zyngier (3):
> arm64: Add cpuidle context save/restore helpers
> arm64: Convert cpu_do_idle() to using cpuidle context helpers
> PSCI: Use cpuidle context helpers in psci_cpu_suspend_enter()
>
> arch/arm/include/asm/cpuidle.h | 5 ++++
> arch/arm64/include/asm/cpuidle.h | 35 +++++++++++++++++++++++++++
> arch/arm64/kernel/process.c | 41 +++++++-------------------------
> drivers/firmware/psci/psci.c | 5 ++++
> 4 files changed, 54 insertions(+), 32 deletions(-)
>
> --
> 2.30.2
>
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next prev parent reply other threads:[~2021-06-10 16:30 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 17:27 [PATCH 0/3] arm64: Fix cpuidle with pseudo-NMI enabled Marc Zyngier
2021-06-08 17:27 ` [PATCH 1/3] arm64: Add cpuidle context save/restore helpers Marc Zyngier
2021-06-11 16:46 ` Lorenzo Pieralisi
2021-06-12 12:04 ` Marc Zyngier
2021-06-16 12:07 ` Lorenzo Pieralisi
2021-06-08 17:27 ` [PATCH 2/3] arm64: Convert cpu_do_idle() to using cpuidle context helpers Marc Zyngier
2021-06-11 16:48 ` Lorenzo Pieralisi
2021-06-08 17:27 ` [PATCH 3/3] PSCI: Use cpuidle context helpers in psci_cpu_suspend_enter() Marc Zyngier
2021-06-08 18:20 ` Sudeep Holla
2021-06-11 16:49 ` Lorenzo Pieralisi
2021-06-09 14:46 ` [PATCH 0/3] arm64: Fix cpuidle with pseudo-NMI enabled Valentin Schneider
2021-06-09 14:58 ` Valentin Schneider
2021-06-10 16:28 ` Lorenzo Pieralisi [this message]
2021-06-10 17:43 ` Sudeep Holla
2021-06-11 8:24 ` Marc Zyngier
2021-06-11 8:19 ` Marc Zyngier
2021-06-11 9:41 ` Lorenzo Pieralisi
2021-06-11 11:32 ` Marc Zyngier
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