Re: [PATCH 2/3] KVM: Centralize slots_lock aquisition during KVM_CREATE_IRQCHIP

Avi Kivity
2010-12-16T09:12:07Z

On 12/15/2010 06:43 PM, Takuya Yoshikawa wrote:
> From: Takuya Yoshikawa<yoshikawa.takuya@oss.ntt.co.jp>
>
> Move slots_lock aquisition from kvm_ioapic_init() and kvm_create_pic()
> to their caller.
>
> As a result, x86's KVM_CREATE_IRQCHIP is now covered by a unified slots_lock
> section, including kvm_setup_default_irq_routing().
>
>

I'm not sure about this...

> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -3300,6 +3300,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
> struct kvm_pic *vpic;
>
> mutex_lock(&kvm->lock);
> + mutex_lock(&kvm->slots_lock);

here, the reader might wonder why we take slots_lock, since we aren't
manipulating anything covered by the lock directly.

> r = -EEXIST;
> if (kvm->arch.vpic)
> goto create_irqchip_unlock;
> @@ -3308,10 +3309,8 @@ long kvm_arch_vm_ioctl(struct file *filp,
> if (vpic) {
> r = kvm_ioapic_init(kvm);
> if (r) {
> - mutex_lock(&kvm->slots_lock);

and here, the reader might wonder why we don't take slots_lock, which
protects io_bus.

Maybe we ought to move slots_lock acquisition to kvm_io_bus_register()
and friends.

--
error compiling committee.c: too many arguments to function