linux-kernel - Re: KVM: x86: question about kvm_ioapic

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Message-ID: <553E27EF.4040505@redhat.com>
Date:	Mon, 27 Apr 2015 14:13:35 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>,
	Julia Lawall <julia.lawall@...6.fr>
CC:	zhanghy@...gfor.com, jasowang@...hat.com, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: KVM: x86: question about kvm_ioapic_destroy



On 27/04/2015 12:05, Michael S. Tsirkin wrote:
> On Sun, Apr 26, 2015 at 07:19:58PM +0200, Julia Lawall wrote:
>> The function kvm_ioapic_destroy is defined as follows:
>>
>> void kvm_ioapic_destroy(struct kvm *kvm)
>> {
>>         struct kvm_ioapic *ioapic = kvm->arch.vioapic;
>>
>>         cancel_delayed_work_sync(&ioapic->eoi_inject);
>>         if (ioapic) {
>>                 kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS, &ioapic->dev);
>>                 kvm->arch.vioapic = NULL;
>>                 kfree(ioapic);
>>         }
>> }
>>
>> Is there any way that cancel_delayed_work_sync can work if ioapic is NULL?  
>> Should the call be moved down under the NULL test?  Or is the NULL test 
>> not needed?  The NULL test has been there longer than the call to 
>> cancel_delayed_work_sync, which was introduced in 184564ef.
> 
> I think the NULL test is not needed.
> kvm_ioapic_destroy is only called if kvm_ioapic_init
> completed successfully, and that sets kvm->arch.vioapic.

Agreed.  By the way, in that case the cancel_delayed_work_sync is really
a nop.

Paolo
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