Re: [PATCH v6 18/23] xen/riscv: implement IRQ routing for device passthrough

[Jan Beulich <jbeulich@xxxxxxxx>]

On 20.07.2026 17:59, Oleksii Kurochko wrote:
> --- a/xen/arch/riscv/Makefile
> +++ b/xen/arch/riscv/Makefile
> @@ -1,6 +1,7 @@
>  obj-y += aia.o
>  obj-y += aplic.o
>  obj-y += cpufeature.o
> +obj-y += device.o

Since you don't permit OVERLAY_DTB=y just yet, this could simply be

obj-y += device.init.o

for the time being. Else use Arm's construct. (And I can't help the feeling
that I did point this out before.)

> @@ -227,3 +253,215 @@ void do_IRQ(struct cpu_user_regs *regs, unsigned int 
> irq)
>      spin_unlock(&desc->lock);
>      irq_exit();
>  }
> +
> +static struct irq_guest *irq_get_guest_info(struct irq_desc *desc)
> +{
> +    ASSERT(spin_is_locked(&desc->lock));
> +    ASSERT(test_bit(_IRQ_GUEST, &desc->status));
> +    ASSERT(desc->action != NULL);
> +
> +    return desc->action->dev_id;
> +}
> +
> +

Nit: Just to remind you - no double blank lines please.

> +/* Route an IRQ to a specific guest */
> +int route_irq_to_guest(struct domain *d, unsigned int virq,
> +                       unsigned int irq, const char *devname)
> +{
> +    struct irqaction *action;
> +    struct irq_guest *info;
> +    struct irq_desc *desc;
> +    unsigned long flags;
> +    int retval = 0;
> +
> +    if ( d->is_dying )
> +        return -EINVAL;
> +
> +    desc = irq_to_desc(irq);
> +
> +    /*
> +     * release_irq() frees this action via xvfree(), relying on action
> +     * being the first member of struct irq_guest so that &info->action
> +     * coincides with info itself. Guard the layout so a future field
> +     * reorder can't silently turn that into a free() of a mid-allocation
> +     * pointer.
> +     */
> +    BUILD_BUG_ON(offsetof(struct irq_guest, action) != 0);

Can't release_irq() simply use container_of()? One way or another it feels
like you're painting yourself into a particular corner ...

With at least the earlier two issues taken care of:
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan