Re: [PATCH v8 13/13] xen/arm: Add support for system suspend triggered by hardware domain

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.04.2026 12:45, Mykola Kvach wrote:
> +/* Xen suspend. data identifies the domain that initiated suspend. */
> +static void system_suspend(void *data)
> +{
> +    int status;
> +    unsigned long flags;
> +    struct domain *d = (struct domain *)data;
> +
> +    BUG_ON(system_state != SYS_STATE_active);
> +
> +    system_state = SYS_STATE_suspend;
> +
> +    printk("Xen suspending...\n");
> +
> +    freeze_domains();
> +    scheduler_disable();
> +
> +    status = can_system_suspend();
> +    if ( status )
> +    {
> +        system_state = SYS_STATE_resume;
> +        goto resume_scheduler;
> +    }
> +
> +    /*
> +     * Non-boot CPUs have to be disabled on suspend and enabled on resume
> +     * (hotplug-based mechanism). Disabling non-boot CPUs will lead to PSCI
> +     * CPU_OFF to be called by each non-boot CPU. Depending on the underlying
> +     * platform capabilities, this may lead to the physical powering down of
> +     * CPUs.
> +     */
> +    status = disable_nonboot_cpus();
> +    if ( status )
> +    {
> +        system_state = SYS_STATE_resume;
> +        goto resume_nonboot_cpus;
> +    }
> +
> +    time_suspend();
> +
> +    status = iommu_suspend();
> +    if ( status )
> +    {
> +        system_state = SYS_STATE_resume;
> +        goto resume_time;
> +    }

So you've frozen the system just to get ...

> --- a/xen/drivers/passthrough/arm/smmu.c
> +++ b/xen/drivers/passthrough/arm/smmu.c
> @@ -2947,6 +2947,13 @@ static void arm_smmu_iommu_domain_teardown(struct 
> domain *d)
>       xfree(xen_domain);
>  }
>  
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +static int arm_smmu_suspend(void)
> +{
> +     return -ENOSYS;
> +}
> +#endif

... unconditional failure from here?

Also, ENOSYS is clearly inappropriate to use here. EOPNOTSUPP or something yet
better distinguishable, please (if this can't be dropped altogether).

Jan