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 11:43:19 +0000 [thread overview]
Message-ID: <53073BD7.4090108@arm.com> (raw)
In-Reply-To: <20140221012358.GB27393@cbox>
On 21/02/14 01:23, Christoffer Dall wrote:
> On Thu, Feb 20, 2014 at 03:26:54PM +0000, Marc Zyngier 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.
>
> This definitely looks correct and is a good solution, so
>
> Acked-by: Christoffer Dall <christoffer.dall@linaro•org>
>
> But see my usual request below.
>
>>
>> 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>
>> ---
>> arch/arm/kvm/arm.c | 3 ++-
>> arch/arm/kvm/interrupts.S | 7 ++++++-
>> arch/arm64/kvm/hyp.S | 9 +++++++--
>> 3 files changed, 15 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index 1d8248e..bd18bb8 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -878,7 +878,8 @@ static int hyp_init_cpu_pm_notifier(struct notifier_block *self,
>> unsigned long cmd,
>> void *v)
>> {
>> - if (cmd == CPU_PM_EXIT) {
>> + if (cmd == CPU_PM_EXIT &&
>> + __hyp_get_vectors() == hyp_default_vectors) {
>> cpu_init_hyp_mode(NULL);
>> return NOTIFY_OK;
>> }
>> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
>> index ddc1553..9b0ff68 100644
>> --- a/arch/arm/kvm/interrupts.S
>> +++ b/arch/arm/kvm/interrupts.S
>> @@ -363,6 +363,11 @@ hyp_hvc:
>> host_switch_to_hyp:
>> pop {r0, r1, r2}
>>
>> + /* Check for __hyp_get_vectors */
>> + cmp r0, #-1
>> + mrceq p15, 4, r0, c12, c0, 0 @ get HVBAR
>> + beq 1f
>> +
>
> I hate to be a stickler about this, but I think the comment explaining
> the KVM/ARM Hypervisor ABI needs to be tweaked (it may have been too
> verbose to begin with), but it should be updated at least to specify the
> special-case handling of r0. I think a small comment somewhere on the
> arm64 part would be similarly nice, but it's not something that should
> hold this patch back.
Good point. I'll add it and repost the patch.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2014-02-21 11:43 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
2014-02-21 14:39 ` Lorenzo Pieralisi
2014-02-21 1:23 ` Christoffer Dall
2014-02-21 11:43 ` Marc Zyngier [this message]
-- 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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