linux-kernel - Re: [PATCH] virt: kvm: arm: vgic: Process the failure case when kvm_register_device

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Message-ID: <54660D33.5090309@arm.com>
Date:	Fri, 14 Nov 2014 14:09:55 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Chen Gang <gang.chen.5i5j@...il.com>
CC:	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	"gleb@...nel.org" <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] virt: kvm: arm: vgic: Process the failure case when kvm_register_device_ops()
 fails

On 14/11/14 14:05, Chen Gang wrote:
> On 11/13/2014 11:30 PM, Marc Zyngier wrote:
>> On 13/11/14 15:04, Chen Gang wrote:
>>> When kvm_register_device_ops() fails, also need call free_percpu_irq()
>>> just like others have down within kvm_vgic_hyp_init().
>>>
>>> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
>>> ---
>>>  virt/kvm/arm/vgic.c | 10 ++++++++--
>>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
>>> index 3aaca49..b799f17 100644
>>> --- a/virt/kvm/arm/vgic.c
>>> +++ b/virt/kvm/arm/vgic.c
>>> @@ -2470,8 +2470,14 @@ int kvm_vgic_hyp_init(void)
>>>  
>>>  	on_each_cpu(vgic_init_maintenance_interrupt, NULL, 1);
>>>  
>>> -	return kvm_register_device_ops(&kvm_arm_vgic_v2_ops,
>>> -				       KVM_DEV_TYPE_ARM_VGIC_V2);
>>> +	ret = kvm_register_device_ops(&kvm_arm_vgic_v2_ops,
>>> +				      KVM_DEV_TYPE_ARM_VGIC_V2);
>>> +	if (ret) {
>>> +		kvm_err("Cannot register device ops\n");
>>> +		goto out_free_irq;
>>> +	}
>>> +
>>> +	return 0;
>>>  
>>>  out_free_irq:
>>>  	free_percpu_irq(vgic->maint_irq, kvm_get_running_vcpus());
>>>
>>
>> Awesome. You're now freeing a per-cpu interrupt after just after having
>> enabled it on all CPUs. What could possibly go wrong?
>>
> 
> OK, thanks. What you said sound reasonable to me. Need call on_each_cpu
> for disable_percpu_irq(). Also need call __unregister_cpu_notifier(),
> and need a new function vgic_arch_unsetup() for arm64.

No. Just look at the code. Why don't you just move the
kvm_register_device_ops call *before* enabling the interrupt?

	M.
-- 
Jazz is not dead. It just smells funny...

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