Re: [RFC PATCH 16/49] ARM: GIC: allow reading pending state of a hardware IRQ

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

Hi Andre,

On 09/02/18 14:39, 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 not CPU field in the
> prototype.
> 
> Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
> ---
>   xen/arch/arm/gic-v2.c     |  6 ++++++
>   xen/arch/arm/gic-v3.c     | 13 +++++++++++++
>   xen/arch/arm/gic.c        |  5 +++++
>   xen/include/asm-arm/gic.h |  5 +++++
>   4 files changed, 29 insertions(+)
> 
> diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
> index 5339f69fbc..30081640ac 100644
> --- a/xen/arch/arm/gic-v2.c
> +++ b/xen/arch/arm/gic-v2.c
> @@ -514,6 +514,11 @@ static unsigned int gicv2_read_apr(int apr_reg)
>      return readl_gich(GICH_APR);
>   }
>   
> +bool gicv2_read_pending_state(int irq)

static

Also, I would like to see the irq turned into irq_desc to match the 
other interface.

> +{
> +    return readl_gicd(GICD_ISPENDR + (irq / 32) * 4) & (1U << (irq % 32));

See my remark in the previous patch. You might want to introduce an 
helper peek.

> +}
> +
>   static void gicv2_irq_enable(struct irq_desc *desc)
>   {
>       unsigned long flags;
> @@ -1261,6 +1266,7 @@ 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 595eaef43a..2cbfeb8e03 100644
> --- a/xen/arch/arm/gic-v3.c
> +++ b/xen/arch/arm/gic-v3.c
> @@ -1081,6 +1081,18 @@ static unsigned int gicv3_read_apr(int apr_reg)
>       }
>   }
>   
> +static bool gicv3_read_pending_state(int irq)
> +{
> +    void __iomem *base;
> +
> +    if ( irq >= NR_GIC_LOCAL_IRQS)
> +        base = GICD + (irq / 32) * 4;
> +    else
> +        base = GICD_RDIST_SGI_BASE;
> +
> +    return readl(base + GICD_ISPENDR) & (1U << (irq % 32));

Looking at the GICv3 code we don't have a peek helper. It is probably 
worth to add one.

> +}
> +
>   static void gicv3_irq_enable(struct irq_desc *desc)
>   {
>       unsigned long flags;
> @@ -1749,6 +1761,7 @@ 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/arch/arm/gic.c b/xen/arch/arm/gic.c
> index dfc2108c4d..ce9ab2367e 100644
> --- a/xen/arch/arm/gic.c
> +++ b/xen/arch/arm/gic.c
> @@ -116,6 +116,11 @@ static void gic_set_irq_priority(struct irq_desc *desc, unsigned int priority)
>       gic_hw_ops->set_irq_priority(desc, priority);
>   }
>   
> +bool gic_read_pending_state(int irq)
> +{
> +    return gic_hw_ops->read_pending_state(irq);
> +}
> +
>   /* Program the GIC to route an interrupt to the host (i.e. Xen)
>    * - needs to be called with desc.lock held
>    */
> diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
> index d330860580..d7fd18fd47 100644
> --- a/xen/include/asm-arm/gic.h
> +++ b/xen/include/asm-arm/gic.h
> @@ -244,6 +244,9 @@ void gic_set_active_state(int irq, bool state);
>   /* Program the IRQ type into the GIC */
>   void gic_set_irq_type(struct irq_desc *desc, unsigned int type);
>   
> +/* Read the pending state of an interrupt from the distributor. */
> +bool gic_read_pending_state(int irq);
> +
>   /* Program the GIC to route an interrupt */
>   extern void gic_route_irq_to_xen(struct irq_desc *desc, unsigned int priority);
>   extern int gic_route_irq_to_guest(struct domain *, unsigned int virq,
> @@ -376,6 +379,8 @@ 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)(int irq);
>       /* Secondary CPU init */
>       int (*secondary_init)(void);
>       /* Create GIC node for the hardware domain */
> 

Cheers,

-- 
Julien Grall

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