From: marc.zyngier@arm•com (Marc Zyngier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] arm/arm64: KVM: detect CPU reset on CPU_PM_EXIT
Date: Fri, 21 Feb 2014 11:20:54 +0000 [thread overview]
Message-ID: <53073696.5080005@arm.com> (raw)
In-Reply-To: <20140220233543.1836e2d5@slackpad>
On 20/02/14 22:35, Andre Przywara wrote:
> On Thu, 20 Feb 2014 15:26:54 +0000
> Marc Zyngier <marc.zyngier@arm•com> wrote:
>
>> Commit 1fcf7ce0c602 (arm: kvm: implement CPU PM notifier) added
>> support for CPU power-management, using a cpu_nofigier to re-init
>> KVM on a CPU that entered CPU idle.
>>
>> The code assumed that a CPU entering idle would actually be powered
>> off, loosing its state entierely, and would then need to be
>> reinitialized. It turns out that this is not always the case, and
>> some HW performs CPU PM without actually killing the core. In this
>> case, we try to reinitialize KVM while it still live. It ends up
>> badly, as reported by Andre Przywara (using a Calxeda Midway):
>>
>> [ 3.663897] Kernel panic - not syncing: unexpected prefetch abort
>> in Hyp mode at: 0x685760 [ 3.663897] unexpected data abort in Hyp
>> mode at: 0xc067d150 [ 3.663897] unexpected HVC/SVC trap in Hyp
>> mode at: 0xc0901dd0
>>
>> The trick here is to detect if we've been through a full re-init or
>> not by looking at HVBAR (VBAR_EL2 on arm64). This involves
>> implementing the backend for __hyp_get_vectors in the main KVM HYP
>> code (rather small), and checking the return value against the
>> default one when the CPU notifier is called on CPU_PM_EXIT.
>>
>> Reported-by: Andre Przywara <osp@andrep•de>
>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm•com>
>> Cc: Rob Herring <rob.herring@linaro•org>
>> Signed-off-by: Marc Zyngier <marc.zyngier@arm•com>
>
> Tested-by: Andre Przywara <osp@andrep•de>
Thanks!
> (there seems to be a typo in the second line of the commit message)
Ah, good katsh! ;-)
> Marc,
>
> thanks a lot for this quick and perfectly working patch! I still
> believe it is actually the firmware that needs to be fixed, but this is
> rather unlikely in this special case ...
Well, that is completely debatable. This is a valid (if minimal)
implementation of cpu idle, and the KVM code *must* be robust enough to
deal with that kind of implementation.
Cheers,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2014-02-21 11:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-20 15:26 [PATCH] arm/arm64: KVM: detect CPU reset on CPU_PM_EXIT Marc Zyngier
2014-02-20 22:35 ` Andre Przywara
2014-02-21 1:24 ` Christoffer Dall
2014-02-21 11:20 ` Marc Zyngier [this message]
2014-02-21 14:39 ` Lorenzo Pieralisi
2014-02-21 1:23 ` Christoffer Dall
2014-02-21 11:43 ` Marc Zyngier
-- strict thread matches above, loose matches on Subject: below --
2014-02-26 18:47 Marc Zyngier
2014-02-26 20:32 ` Paolo Bonzini
2014-02-27 18:27 ` Paolo Bonzini
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