HI. I'm now modifying GIC in Xen 4.5.0. I have some question about lock of pending_irq struct in Xen ARM. pending_irq of SGI and PPI is stored in 'vcpu struct'. (IRQ num 0 ~ 31) pending_irq of SPI is stored in 'domain struct'. (IRQ num 32 ~ ) For accessing pending_irq struct, Xen use 'irq_to_pending(struct vcpu *v, int irq)' function. irq_to_pending function return proper pending_irq depending on IRQ number. * 'gic_update_one_lr' function process 1) before call gic_update_one_lr, xen acquire like this "spin_lock_irqsave(&v->arch.vgic.lock, flags)"; 2) In gic_update_one_lr, get pending_irq through irq_to_pending function. 3) change state of irq_to_pending and update lr When IRQ number is below 31, irq_to_pending function return pending_irq stored in vcpu struct. It's ok to change irq_to_pending state, because &v->arch.vgic.lock acquire. But When IRQ number is above 32, irq_to_pending function return pending_irq stored in domain struct. And change state of irq_to_pending without domain's lock. I think that pending_irq of SPI stored in domain struct is shared among vcpus. and need to acquire domain's lock before change pending_irq. But why don't use domain's lock in Xen Code ?? Thanks. * Sorry for my poor english skill..
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