On Tue, Sep 11, 2012 at 2:50 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> __kvm_vgic_sync_from_cpu() doesn't really touch the distributor itself,
> as the irq_pending_on_cpu access doesn't really need any locking.
>
> Remove the corresponding spin_lock() access from kvm_vgic_sync_from_cpu().
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/kvm/vgic.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/arm/kvm/vgic.c b/arch/arm/kvm/vgic.c
> index b77f8bf..9cac7b2 100644
> --- a/arch/arm/kvm/vgic.c
> +++ b/arch/arm/kvm/vgic.c
> @@ -790,7 +790,9 @@ epilog:
> }
>
> /*
> - * Sync back the VGIC state after a guest run.
> + * Sync back the VGIC state after a guest run. We do not really touch
> + * the distributor here (the irq_pending_on_cpu bit is safe to set),
> + * so there is no need for taking its lock.
> */
> static void __kvm_vgic_sync_from_cpu(struct kvm_vcpu *vcpu)
> {
> @@ -815,8 +817,10 @@ static void __kvm_vgic_sync_from_cpu(struct kvm_vcpu *vcpu)
> /* Check if we still have something up our sleeve... */
> pending = find_first_zero_bit((unsigned long *)vgic_cpu->vgic_elrsr,
> vgic_cpu->nr_lr);
> - if (pending < vgic_cpu->nr_lr)
> + if (pending < vgic_cpu->nr_lr) {
> set_bit(vcpu->vcpu_id, &dist->irq_pending_on_cpu);
> + smp_mb();
> + }
> }
>
> void kvm_vgic_sync_to_cpu(struct kvm_vcpu *vcpu)
> @@ -833,14 +837,10 @@ void kvm_vgic_sync_to_cpu(struct kvm_vcpu *vcpu)
>
> void kvm_vgic_sync_from_cpu(struct kvm_vcpu *vcpu)
> {
> - struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> -
> if (!irqchip_in_kernel(vcpu->kvm))
> return;
>
> - spin_lock(&dist->lock);
> __kvm_vgic_sync_from_cpu(vcpu);
> - spin_unlock(&dist->lock);
> }
>
> int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu)
> --
> 1.7.12
>
Thanks,
applied
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