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

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Message-ID: <20150427120342-mutt-send-email-mst@redhat.com>
Date:	Mon, 27 Apr 2015 12:05:33 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Julia Lawall <julia.lawall@...6.fr>
Cc:	zhanghy@...gfor.com, jasowang@...hat.com, pbonzini@...hat.com,
	x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: KVM: x86: question about kvm_ioapic_destroy

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.
> 
> thanks,
> julia

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.

-- 
MST
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