xen/event: Add reference counting to event channels
Event channels exposed to userspace by the evtchn module may be used by
other modules in an asynchronous manner, which requires that reference
counting be used to prevent the event channel from being closed before
the signals are delivered.
The reference count on new event channels defaults to -1 which indicates
the event channel is not referenced outside the kernel; evtchn_get fails
if called on such an event channel. The event channels made visible to
userspace by evtchn have a normal reference count.
Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 6e075cd..a3bcd61 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -87,6 +87,7 @@
*/
struct irq_info {
struct list_head list;
+ int refcnt;
enum xen_irq_type type; /* type */
unsigned irq;
unsigned short evtchn; /* event channel */
@@ -406,6 +407,7 @@
panic("Unable to allocate metadata for IRQ%d\n", irq);
info->type = IRQT_UNBOUND;
+ info->refcnt = -1;
irq_set_handler_data(irq, info);
@@ -469,6 +471,8 @@
irq_set_handler_data(irq, NULL);
+ WARN_ON(info->refcnt > 0);
+
kfree(info);
/* Legacy IRQ descriptors are managed by the arch. */
@@ -637,7 +641,7 @@
if (irq != -1) {
printk(KERN_INFO "xen_map_pirq_gsi: returning irq %d for gsi %u\n",
irq, gsi);
- goto out; /* XXX need refcount? */
+ goto out;
}
irq = xen_allocate_irq_gsi(gsi);
@@ -939,9 +943,16 @@
{
struct evtchn_close close;
int evtchn = evtchn_from_irq(irq);
+ struct irq_info *info = irq_get_handler_data(irq);
mutex_lock(&irq_mapping_update_lock);
+ if (info->refcnt > 0) {
+ info->refcnt--;
+ if (info->refcnt != 0)
+ goto done;
+ }
+
if (VALID_EVTCHN(evtchn)) {
close.port = evtchn;
if (HYPERVISOR_event_channel_op(EVTCHNOP_close, &close) != 0)
@@ -970,6 +981,7 @@
xen_free_irq(irq);
+ done:
mutex_unlock(&irq_mapping_update_lock);
}
@@ -1065,6 +1077,66 @@
}
EXPORT_SYMBOL_GPL(unbind_from_irqhandler);
+int evtchn_make_refcounted(unsigned int evtchn)
+{
+ int irq = evtchn_to_irq[evtchn];
+ struct irq_info *info;
+
+ if (irq == -1)
+ return -ENOENT;
+
+ info = irq_get_handler_data(irq);
+
+ if (!info)
+ return -ENOENT;
+
+ WARN_ON(info->refcnt != -1);
+
+ info->refcnt = 1;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(evtchn_make_refcounted);
+
+int evtchn_get(unsigned int evtchn)
+{
+ int irq;
+ struct irq_info *info;
+ int err = -ENOENT;
+
+ mutex_lock(&irq_mapping_update_lock);
+
+ irq = evtchn_to_irq[evtchn];
+ if (irq == -1)
+ goto done;
+
+ info = irq_get_handler_data(irq);
+
+ if (!info)
+ goto done;
+
+ err = -EINVAL;
+ if (info->refcnt <= 0)
+ goto done;
+
+ info->refcnt++;
+ err = 0;
+ done:
+ mutex_unlock(&irq_mapping_update_lock);
+
+ return err;
+}
+EXPORT_SYMBOL_GPL(evtchn_get);
+
+void evtchn_put(unsigned int evtchn)
+{
+ int irq = evtchn_to_irq[evtchn];
+ if (WARN_ON(irq == -1))
+ return;
+ unbind_from_irq(irq);
+}
+EXPORT_SYMBOL_GPL(evtchn_put);
+
void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
{
int irq = per_cpu(ipi_to_irq, cpu)[vector];
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index dbc13e9..b1f60a0 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -268,7 +268,7 @@
rc = bind_evtchn_to_irqhandler(port, evtchn_interrupt, IRQF_DISABLED,
u->name, (void *)(unsigned long)port);
if (rc >= 0)
- rc = 0;
+ rc = evtchn_make_refcounted(port);
return rc;
}
diff --git a/include/xen/events.h b/include/xen/events.h
index d287997..0f77370 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -37,6 +37,13 @@
*/
void unbind_from_irqhandler(unsigned int irq, void *dev_id);
+/*
+ * Allow extra references to event channels exposed to userspace by evtchn
+ */
+int evtchn_make_refcounted(unsigned int evtchn);
+int evtchn_get(unsigned int evtchn);
+void evtchn_put(unsigned int evtchn);
+
void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector);
int resend_irq_on_evtchn(unsigned int irq);
void rebind_evtchn_irq(int evtchn, int irq);
