[Xen-devel] [PATCH v3] Use PHYSDEVOP_get_free_pirq to implement find_unbound_pirq

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

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 v2:

- simplify the loop in find_unbound_pirq.


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@xxxxxxxxxxxxx>

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 2811bb9..6e5dd92 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; i++) {
                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 {
+    /* IN */ 
+    int type;
+    /* OUT */
+    uint32_t pirq;
+};
+
 /*
  * Notify that some PIRQ-bound event channels have been unmasked.
  * ** This command is obsolete since interface version 0x00030202 and is **

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