Re: [PATCH v4 8/9] xen/riscv: implement setup_irq()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 05.06.2025 17:59, Oleksii Kurochko wrote:
> Introduce support for IRQ setup on RISC-V by implementing setup_irq() and
> __setup_irq(), adapted and extended from an initial implementation by [1].
> 
> __setup_irq() does the following:
>   - Sets up an IRQ action.
>   - Validates that shared IRQs have non-NULL `dev_id` and are only used when
>     existing handlers allow sharing.
>   - Uses smp_wmb() to enforce memory ordering after assigning desc->action
>     to ensure visibility before enabling the IRQ.
>   - Supports multi-action setups via CONFIG_IRQ_HAS_MULTIPLE_ACTION.
> 
> setup_irq() does the following:
>   - Converts IRQ number to descriptor and acquires its lock.
>   - Rejects registration if the IRQ is already assigned to a guest domain,
>     printing an error.
>   - Delegates the core setup to __setup_irq().
>   - On first-time setup, disables the IRQ, routes it to Xen using
>     intc_route_irq_to_xen(), sets default CPU affinity (current CPU),
>     calls the handler’s startup routine, and finally enables the IRQ.
> 
> irq_set_affinity() invokes set_affinity() callback from the IRQ handler
> if present.
> 
> Defined IRQ_NO_PRIORITY as default priority used when routing IRQs to Xen.
> 
> [1] 
> https://gitlab.com/xen-project/people/olkur/xen/-/commit/7390e2365828b83e27ead56b03114a56e3699dd5
> 
> Co-developed-by: Romain Caritey <Romain.Caritey@xxxxxxxxxxxxx>
> Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>