Re: [Xen-devel] [PATCH v3 03/39] ARM: GIC: Allow tweaking the active and pending state of an IRQ

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/21/2018 04:31 PM, Andre Przywara wrote:
> When playing around with hardware mapped, level triggered virtual IRQs,
> there is the need to explicitly set the active or pending state of an
> interrupt at some point.
> To prepare the GIC for that, we introduce a set_active_state() and a
> set_pending_state() function to let the VGIC manipulate the state of
> an associated hardware IRQ.
> This takes care of properly setting the _IRQ_INPROGRESS bit.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
> ---
> Changelog v2 ... v3:
> - rework setting _IRQ_INPROGRESS bit:
>    - no change when changing active state
>    - unconditional set/clear on changing pending state
> - drop introduction of gicv[23]_peek_irq() (only needed in the next patch now)
>
> Changelog v1 ... v2:
> - properly set _IRQ_INPROGRESS bit
> - add gicv[23]_peek_irq() (pulled in from later patch)
> - move wrappers functions into gic.h
>
>   xen/arch/arm/gic-v2.c     | 36 ++++++++++++++++++++++++++++++++++++
>   xen/arch/arm/gic-v3.c     | 32 ++++++++++++++++++++++++++++++++
>   xen/include/asm-arm/gic.h | 24 ++++++++++++++++++++++++
>   3 files changed, 92 insertions(+)
>
> diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
> index aa0fc6c1a1..d1f1578c05 100644
> --- a/xen/arch/arm/gic-v2.c
> +++ b/xen/arch/arm/gic-v2.c
> @@ -243,6 +243,40 @@ static void gicv2_poke_irq(struct irq_desc *irqd, uint32_t 
> offset)
>       writel_gicd(1U << (irqd->irq % 32), offset + (irqd->irq / 32) * 4);
>   }
>   
> +static void gicv2_set_active_state(struct irq_desc *irqd, bool active)
> +{
> +    ASSERT(spin_is_locked(&irqd->lock));
> +
> +    if ( active )
> +    {
> +        if ( test_bit(_IRQ_GUEST, &irqd->status) )
I don't understand why you only set/clear INPROGRESS bit for interrupt 
routed to guest. This will matter when releasing interrupt used by Xen 
(see release_irq).
Note that I don't expect this helper to be call on Xen IRQ, but I think 
we should make
Other than same remark on GICv3 code, the pending implementation looks 
good to me now.
Cheers,

--
Julien Grall

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