Re: [PATCH v10 04/32] ARM: vGIC: rework gic_remove_from_queues()

[Julien Grall <julien.grall@arm.com>]

Hi Andre,

On 26/05/17 18:35, Andre Przywara wrote:
> The function name gic_remove_from_queues() was a bit of a misnomer,
> since it just removes an IRQ from the pending queue, not both queues.
> Rename the function to make this more clear, also give it a pointer to
> a struct pending_irq directly and rely on the VGIC VCPU lock to be
> already taken, so this can be used in more places.
> Replace the list removal in gic_clear_pending_irqs() with a call to
> this function.
>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> ---
>  xen/arch/arm/gic.c        | 12 +++---------
>  xen/arch/arm/vgic.c       |  2 +-
>  xen/include/asm-arm/gic.h |  2 +-
>  3 files changed, 5 insertions(+), 11 deletions(-)
>
> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> index dcb1783..9dde146 100644
> --- a/xen/arch/arm/gic.c
> +++ b/xen/arch/arm/gic.c
> @@ -400,18 +400,12 @@ static inline void gic_add_to_lr_pending(struct vcpu *v, struct pending_irq *n)
>      list_add_tail(&n->lr_queue, &v->arch.vgic.lr_pending);
>  }
>
> -void gic_remove_from_queues(struct vcpu *v, unsigned int virtual_irq)
> +void gic_remove_from_lr_pending(struct vcpu *v, struct pending_irq *p)
>  {
> -    struct pending_irq *p;
> -    unsigned long flags;
> -
> -    spin_lock_irqsave(&v->arch.vgic.lock, flags);
> -
> -    p = irq_to_pending(v, virtual_irq);
> +    ASSERT(spin_is_locked(&v->arch.vgic.lock));

Likely something before was wrong if you replace the lock by an ASSERT 
without even adding lock in the current callers. Such as the deadlock 
introduced in the previous patch...

>
>      if ( !list_empty(&p->lr_queue) )

Whilst you rework gic_remove_from_queues, you could probably remove this 
check.

>          list_del_init(&p->lr_queue);
> -    spin_unlock_irqrestore(&v->arch.vgic.lock, flags);
>  }
>
>  void gic_raise_inflight_irq(struct vcpu *v, unsigned int virtual_irq)
> @@ -612,7 +606,7 @@ void gic_clear_pending_irqs(struct vcpu *v)
>
>      v->arch.lr_mask = 0;
>      list_for_each_entry_safe ( p, t, &v->arch.vgic.lr_pending, lr_queue )
> -        list_del_init(&p->lr_queue);
> +        gic_remove_from_lr_pending(v, p);
>  }
>
>  int gic_events_need_delivery(void)
> diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
> index 69d732b..3993965 100644
> --- a/xen/arch/arm/vgic.c
> +++ b/xen/arch/arm/vgic.c
> @@ -325,7 +325,7 @@ void vgic_disable_irqs(struct vcpu *v, uint32_t r, int n)
>          spin_lock_irqsave(&v_target->arch.vgic.lock, flags);
>          p = irq_to_pending(v_target, irq);
>          clear_bit(GIC_IRQ_GUEST_ENABLED, &p->status);
> -        gic_remove_from_queues(v_target, irq);
> +        gic_remove_from_lr_pending(v_target, p);
>          desc = p->desc;
>          spin_unlock_irqrestore(&v_target->arch.vgic.lock, flags);
>
> diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
> index 836a103..3130634 100644
> --- a/xen/include/asm-arm/gic.h
> +++ b/xen/include/asm-arm/gic.h
> @@ -243,7 +243,7 @@ extern void init_maintenance_interrupt(void);
>  extern void gic_raise_guest_irq(struct vcpu *v, unsigned int irq,
>          unsigned int priority);
>  extern void gic_raise_inflight_irq(struct vcpu *v, unsigned int virtual_irq);
> -extern void gic_remove_from_queues(struct vcpu *v, unsigned int virtual_irq);
> +extern void gic_remove_from_lr_pending(struct vcpu *v, struct pending_irq *p);
>
>  /* Accept an interrupt from the GIC and dispatch its handler */
>  extern void gic_interrupt(struct cpu_user_regs *regs, int is_fiq);
>

Cheers,

-- 
Julien Grall

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