Re: [Xen-devel] [PATCH v2] Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Jeremy Fitzhardinge <jeremy@goop.org>]

On 11/24/2010 11:22 AM, 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.
>
> Changes since v1:
>
> - if PHYSDEVOP_get_free_pirq is not implemented, start pirq allocation
> from 0 instead of 16. The pirq number 16 is not actually meaningful for
> Xen.
>
> - Remove nr_pirqs, it is not needed anymore. Add a comment to specify
> that we don't actually know the upper limit of the pirq number range.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>
>
> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> index 2811bb9..072af50 100644
> --- a/drivers/xen/events.c
> +++ b/drivers/xen/events.c
> @@ -105,7 +105,6 @@ struct irq_info
>  
>  static struct irq_info *irq_info;
>  static int *pirq_to_irq;
> -static int nr_pirqs;
>  
>  static int *evtchn_to_irq;
>  struct cpu_evtchn_s {
> @@ -385,12 +384,17 @@ 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 = 0; i <= nr_irqs-1; i++) {

That seems needlessly complex.  What's wrong with "i < nr_irqs"?  Are
you trying to express something specific with this?
>  		if (pirq_to_irq[i] < 0)
>  			return i;
>  	}
> @@ -611,9 +615,9 @@ int xen_map_pirq_gsi(unsigned pirq, unsigned gsi, int shareable, char *name)
>  
>  	spin_lock(&irq_mapping_update_lock);
>  
> -	if ((pirq > nr_pirqs) || (gsi > nr_irqs)) {
> +	if ((pirq > nr_irqs) || (gsi > nr_irqs)) {
>  		printk(KERN_WARNING "xen_map_pirq_gsi: %s %s is incorrect!\n",
> -			pirq > nr_pirqs ? "nr_pirqs" :"",
> +			pirq > nr_irqs ? "nr_pirqs" :"",
>  			gsi > nr_irqs ? "nr_irqs" : "");
>  		goto out;
>  	}
> @@ -672,7 +676,7 @@ 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;
>  
> @@ -1506,26 +1510,17 @@ void xen_callback_vector(void) {}
>  
>  void __init xen_init_IRQ(void)
>  {
> -	int i, rc;
> -	struct physdev_nr_pirqs op_nr_pirqs;
> +	int i;
>  
>  	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;
> -	}
> -	pirq_to_irq = kcalloc(nr_pirqs, sizeof(*pirq_to_irq), GFP_KERNEL);
> -	for (i = 0; i < nr_pirqs; i++)
> +	/* We are using nr_irqs as the maximum number of pirq available but
> +	 * that number is actually chosen by Xen and we don't know exactly
> +	 * what it is. Be careful choosing high pirq numbers. */
> +	pirq_to_irq = kcalloc(nr_irqs, sizeof(*pirq_to_irq), GFP_KERNEL);
> +	for (i = 0; i < nr_irqs; i++)
>  		pirq_to_irq[i] = -1;
>  
>  	evtchn_to_irq = kcalloc(NR_EVENT_CHANNELS, sizeof(*evtchn_to_irq),
> diff --git a/include/xen/interface/physdev.h b/include/xen/interface/physdev.h
> index 2b2c66c..534cac8 100644
> --- a/include/xen/interface/physdev.h
> +++ b/include/xen/interface/physdev.h
> @@ -188,6 +188,16 @@ struct physdev_nr_pirqs {
>      uint32_t nr_pirqs;
>  };
>  
> +/* type is MAP_PIRQ_TYPE_GSI or MAP_PIRQ_TYPE_MSI
> + * the hypercall returns a free pirq */
> +#define PHYSDEVOP_get_free_pirq    23
> +struct physdev_get_free_pirq {

I guess it doesn't really matter, and it's probably a bit late, but this
seems like an odd name.  Normally I'd think of this as an allocation, so
something like PHYSDEVOP_alloc_pirq.

    J