Re: [Xen-devel] [RFC PATCH 43/49] ARM: new VGIC: Add preliminary stub implementations

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 09/02/18 14:39, Andre Przywara wrote:
> The Xen core code requires an interrupt controller emulation to implement
> arch_move_irqs(), to move the affinity of an hardware mapped virtual IRQ
> to another core. In the moment we don't implement this
> physical-follow-virtual regime in our new VGIC, so just provide an empty
> stub implementation to make the linker happy.
physical-follow-virtual is a must feature for the new vGIC. This has 
shown better interrupt latency.
> Similarily vgic_clear_pending_irqs() is required by the ARM code,
> although it is suspected that it is actually not necessary. Go with a
> stub for now.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
> ---
>   xen/arch/arm/vgic/vgic.c | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/xen/arch/arm/vgic/vgic.c b/xen/arch/arm/vgic/vgic.c
> index d91028bd43..77fa756329 100644
> --- a/xen/arch/arm/vgic/vgic.c
> +++ b/xen/arch/arm/vgic/vgic.c
> @@ -770,6 +770,19 @@ void gic_dump_vgic_info(struct vcpu *v)
>                  irq->active ? "" : "not ", irq->enabled ? "" : "not ");
>   }
>   
> +void vgic_clear_pending_irqs(struct vcpu *v)
> +{
> +    /*
> +     * TODO: It is unclear whether we really need this, so we might instead
> +     * remove it on the caller site.
> +     */
I remember some issue with the current vGIC when not removing pending 
interrupts on PSCI CPU ON. But that was a while ago. I will have another 
try and see if we can drop it.
> +}
> +
> +void arch_move_irqs(struct vcpu *v)
> +{
> +    /* TODO: implement this (?) */
Here you would need to go through the interrupt and modify the affinity 
of the physical IRQs routed to that vCPU.
> +}
> +
>   struct irq_desc *vgic_get_hw_irq_desc(struct domain *d, struct vcpu *v,
>                                         unsigned int virq)
>   {
Cheers,

--
Julien Grall

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