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    SubjectRe: [PATCH] xen: use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq
    On Sat, Nov 20, 2010 at 01:19:31AM +0000, Stefano Stabellini wrote:
    > On Fri, 19 Nov 2010, Konrad Rzeszutek Wilk wrote:
    > > 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--) {
    > >
    >
    > Because we don't know the real nr_pirqs anymore (PHYSDEVOP_get_nr_pirqs
    > has been removed), so it is highly possible that starting from the top
    > down would give us pirq numbers out of range in Xen. Therefore we need
    > to start from the bottom up, and the bottom for Xen is 16.

    Right, I forgot about the hypercall call. How about using LEGACY_IRQ instead then?

    >
    >
    > > > 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?
    > >
    >
    > Yeah, I guess we could do that. I kept it around just to make it more
    > obvious that the max pirq number is different from nr_irqs and we don't
    > know what the exact value is.


    But with this change it is the same, is it not?

    "nr_pirgs = nr_irqs;"

    Or when you say "max pirq" you are referring to something else altogether?


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