Re: [PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Nov 19, 2010 at 01:58:03PM +0000, Stefano Stabellini wrote:
> Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq
> 
> Use the new hypercall PHYSDEVOP_get_free_pirq to ask Xen to allocate a
> pirq. Remove the unsupported PHYSDEVOP_get_nr_pirqs hypercall to get the
> amount of pirq available.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> 
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index 321a0c8..ffd286e 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -382,12 +382,17 @@ static int get_nr_hw_irqs(void)
>  	return ret;
>  }
>  
> -/* callers of this function should make sure that PHYSDEVOP_get_nr_pirqs
> - * succeeded otherwise nr_pirqs won't hold the right value */
> -static int find_unbound_pirq(void)
> +static int find_unbound_pirq(int type)
>  {
> -	int i;
> -	for (i = nr_pirqs-1; i >= 0; i--) {
> +	int rc, i;
> +	struct physdev_get_free_pirq op_get_free_pirq;
> +	op_get_free_pirq.type = type;
> +
> +	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_free_pirq, &op_get_free_pirq);
> +	if (!rc)
> +		return op_get_free_pirq.pirq;
> +
> +	for (i = 16; i <= nr_pirqs-1; i++) {

16? No no. Why not re-use the old loop, like so:

 	for (i = nr_pirqs-1; i >= 0; i--) {

>  		if (pirq_to_irq[i] < 0)
>  			return i;
>  	}
> @@ -669,7 +674,7 @@ void xen_allocate_pirq_msi(char *name, int *irq, int *pirq)
>  	if (*irq == -1)
>  		goto out;
>  
> -	*pirq = find_unbound_pirq();
> +	*pirq = find_unbound_pirq(MAP_PIRQ_TYPE_MSI);
>  	if (*pirq == -1)
>  		goto out;
>  
> @@ -1504,23 +1509,12 @@ void xen_callback_vector(void) {}
>  void __init xen_init_IRQ(void)
>  {
>  	int i, rc;
> -	struct physdev_nr_pirqs op_nr_pirqs;
>  
>  	cpu_evtchn_mask_p = kcalloc(nr_cpu_ids, sizeof(struct cpu_evtchn_s),
>  				    GFP_KERNEL);
>  	irq_info = kcalloc(nr_irqs, sizeof(*irq_info), GFP_KERNEL);
>  
> -	rc = HYPERVISOR_physdev_op(PHYSDEVOP_get_nr_pirqs, &op_nr_pirqs);
> -	if (rc < 0) {
> -		nr_pirqs = nr_irqs;
> -		if (rc != -ENOSYS)
> -			printk(KERN_WARNING "PHYSDEVOP_get_nr_pirqs returned rc=%d\n", rc);
> -	} else {
> -		if (xen_pv_domain() && !xen_initial_domain())
> -			nr_pirqs = max((int)op_nr_pirqs.nr_pirqs, nr_irqs);
> -		else
> -			nr_pirqs = op_nr_pirqs.nr_pirqs;
> -	}
> +	nr_pirqs = nr_irqs;

Why not just get rid of nr_pirgs altogether then? And use 'nr_irqs' instead?