Re: [Xen-devel] [PATCH v2 10/45] ARM: GIC: Allow reading pending state of a hardware IRQ

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 03/15/2018 08:30 PM, Andre Przywara wrote:
> To synchronize level triggered interrupts which are mapped into a guest,
> we need to update the virtual line level at certain points in time.
> For a hardware mapped interrupt the GIC is the only place where we can
> easily access this information.
> Implement a gic_hw_operations member to return the pending state of a
> particular interrupt. Due to hardware limitations this only works for
> private interrupts of the current CPU, so there is no CPU field in the
> prototype.
> This adds gicv2/3_peek_irq() helper functions, to read a bit in a bitmap
> spread over several MMIO registers.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
Reviewed-by: Julien Grall <julien.grall@xxxxxxx>

Cheers,

> ---
> Changelog v1 ... v2:
> - remove introduction of gicv[23]_peek_irq() (now one patch earlier)
> - move wrapper functions into gic.h
>
>   xen/arch/arm/gic-v2.c     |  6 ++++++
>   xen/arch/arm/gic-v3.c     |  6 ++++++
>   xen/include/asm-arm/gic.h | 11 +++++++++++
>   3 files changed, 23 insertions(+)
>
> diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
> index c6fcbf59d0..52880d658c 100644
> --- a/xen/arch/arm/gic-v2.c
> +++ b/xen/arch/arm/gic-v2.c
> @@ -591,6 +591,11 @@ static unsigned int gicv2_read_apr(int apr_reg)
>      return readl_gich(GICH_APR);
>   }
>   
> +static bool gicv2_read_pending_state(struct irq_desc *irqd)
> +{
> +    return gicv2_peek_irq(irqd, GICD_ISPENDR);
> +}
> +
>   static void gicv2_irq_enable(struct irq_desc *desc)
>   {
>       unsigned long flags;
> @@ -1336,6 +1341,7 @@ const static struct gic_hw_operations gicv2_ops = {
>       .write_lr            = gicv2_write_lr,
>       .read_vmcr_priority  = gicv2_read_vmcr_priority,
>       .read_apr            = gicv2_read_apr,
> +    .read_pending_state  = gicv2_read_pending_state,
>       .make_hwdom_dt_node  = gicv2_make_hwdom_dt_node,
>       .make_hwdom_madt     = gicv2_make_hwdom_madt,
>       .get_hwdom_extra_madt_size = gicv2_get_hwdom_extra_madt_size,
> diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
> index 316f2c4142..008be87572 100644
> --- a/xen/arch/arm/gic-v3.c
> +++ b/xen/arch/arm/gic-v3.c
> @@ -1161,6 +1161,11 @@ static unsigned int gicv3_read_apr(int apr_reg)
>       }
>   }
>   
> +static bool gicv3_read_pending_state(struct irq_desc *irqd)
> +{
> +    return gicv3_peek_irq(irqd, GICD_ISPENDR);
> +}
> +
>   static void gicv3_irq_enable(struct irq_desc *desc)
>   {
>       unsigned long flags;
> @@ -1829,6 +1834,7 @@ static const struct gic_hw_operations gicv3_ops = {
>       .write_lr            = gicv3_write_lr,
>       .read_vmcr_priority  = gicv3_read_vmcr_priority,
>       .read_apr            = gicv3_read_apr,
> +    .read_pending_state  = gicv3_read_pending_state,
>       .secondary_init      = gicv3_secondary_cpu_init,
>       .make_hwdom_dt_node  = gicv3_make_hwdom_dt_node,
>       .make_hwdom_madt     = gicv3_make_hwdom_madt,
> diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
> index 21cf35f106..bd7802667f 100644
> --- a/xen/include/asm-arm/gic.h
> +++ b/xen/include/asm-arm/gic.h
> @@ -372,6 +372,8 @@ struct gic_hw_operations {
>       unsigned int (*read_vmcr_priority)(void);
>       /* Read APRn register */
>       unsigned int (*read_apr)(int apr_reg);
> +    /* Query the pending state of an interrupt at the distributor level. */
> +    bool (*read_pending_state)(struct irq_desc *irqd);
>       /* Secondary CPU init */
>       int (*secondary_init)(void);
>       /* Create GIC node for the hardware domain */
> @@ -416,6 +418,15 @@ static inline void gic_set_pending_state(struct irq_desc 
> *irqd, bool state)
>       gic_hw_ops->set_pending_state(irqd, state);
>   }
>   
> +/*
> + * Read the pending state of an interrupt from the distributor.
> + * For private IRQs this only works for those of the current CPU.
> + */
> +static inline bool gic_read_pending_state(struct irq_desc *irqd)
> +{
> +    return gic_hw_ops->read_pending_state(irqd);
> +}
> +
>   void register_gic_ops(const struct gic_hw_operations *ops);
>   int gic_make_hwdom_dt_node(const struct domain *d,
>                              const struct dt_device_node *gic,
--
Julien Grall

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