From: Marc Zyngier <maz@kernel.org>
To: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Mark Rutland <mark.rutland@arm.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Will Deacon <will@kernel.org>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Sudeep Holla <sudeep.holla@arm.com>,
David Brazdil <dbrazdil@google.com>,
kernel-team@android.com, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return
Date: Wed, 30 Dec 2020 10:06:19 +0000 [thread overview]
Message-ID: <0e1d555404e4ae8edcf6737735dc0eb7@kernel.org> (raw)
In-Reply-To: <20201229170412.GN1551@shell.armlinux.org.uk>
On 2020-12-29 17:04, Russell King - ARM Linux admin wrote:
> On Tue, Dec 29, 2020 at 04:00:59PM +0000, David Brazdil wrote:
>> The KVM/arm64 PSCI relay assumes that SYSTEM_OFF and SYSTEM_RESET
>> should
>> not return, as dictated by the PSCI spec. However, there is firmware
>> out
>> there which breaks this assumption, leading to a hyp panic. Make KVM
>> more robust to broken firmware by allowing these to return.
>
> Are you sure you should just return?
>
> We've had issues in the past with Linux reboot(2) that returns
> to userspace, allowing on 32-bit ARM for example watchdogs to
> unexpectedly continue being serviced.
I don't think this changes anything compared to the case where
the PSCI relay isn't enabled. The EL1 part of the kernel would
see the SYSTEM_RESET call return, and handle it accordingly
(stay in a while(1) loop).
This is consistent with the PSCI relay design goal of being
invisible to the EL1 kernel.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-12-30 10:07 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-29 16:00 [PATCH] KVM: arm64: Allow PSCI SYSTEM_OFF/RESET to return David Brazdil
2020-12-29 17:04 ` Russell King - ARM Linux admin
2020-12-30 10:06 ` Marc Zyngier [this message]
2020-12-29 17:16 ` Marc Zyngier
2020-12-30 11:03 ` David Brazdil
2021-01-15 11:33 ` Marc Zyngier
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