xen/events: add a new "late EOI" evtchn framework

commit 54c9de89895e0a36047fcc4ae754ea5b8655fb9d upstream.

In order to avoid tight event channel related IRQ loops add a new
framework of "late EOI" handling: the IRQ the event channel is bound
to will be masked until the event has been handled and the related
driver is capable to handle another event. The driver is responsible
for unmasking the event channel via the new function xen_irq_lateeoi().

This is similar to binding an event channel to a threaded IRQ, but
without having to structure the driver accordingly.

In order to support a future special handling in case a rogue guest
is sending lots of unsolicited events, add a flag to xen_irq_lateeoi()
which can be set by the caller to indicate the event was a spurious
one.

This is part of XSA-332.

Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 25 insertions, 4 deletions

diff --git a/include/xen/events.h b/include/xen/events.h
index 88da2abaf535..ad0c61cf399b 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -12,11 +12,16 @@
 
 unsigned xen_evtchn_nr_channels(void);
 
-int bind_evtchn_to_irq(unsigned int evtchn);
-int bind_evtchn_to_irqhandler(unsigned int evtchn,
+int bind_evtchn_to_irq(evtchn_port_t evtchn);
+int bind_evtchn_to_irq_lateeoi(evtchn_port_t evtchn);
+int bind_evtchn_to_irqhandler(evtchn_port_t evtchn,
 			      irq_handler_t handler,
 			      unsigned long irqflags, const char *devname,
 			      void *dev_id);
+int bind_evtchn_to_irqhandler_lateeoi(evtchn_port_t evtchn,
+				      irq_handler_t handler,
+				      unsigned long irqflags, const char *devname,
+				      void *dev_id);
 int bind_virq_to_irq(unsigned int virq, unsigned int cpu, bool percpu);
 int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
 			    irq_handler_t handler,
@@ -29,13 +34,21 @@ int bind_ipi_to_irqhandler(enum ipi_vector ipi,
 			   const char *devname,
 			   void *dev_id);
 int bind_interdomain_evtchn_to_irq(unsigned int remote_domain,
-				   unsigned int remote_port);
+				   evtchn_port_t remote_port);
+int bind_interdomain_evtchn_to_irq_lateeoi(unsigned int remote_domain,
+					   evtchn_port_t remote_port);
 int bind_interdomain_evtchn_to_irqhandler(unsigned int remote_domain,
-					  unsigned int remote_port,
+					  evtchn_port_t remote_port,
 					  irq_handler_t handler,
 					  unsigned long irqflags,
 					  const char *devname,
 					  void *dev_id);
+int bind_interdomain_evtchn_to_irqhandler_lateeoi(unsigned int remote_domain,
+						  evtchn_port_t remote_port,
+						  irq_handler_t handler,
+						  unsigned long irqflags,
+						  const char *devname,
+						  void *dev_id);
 
 /*
  * Common unbind function for all event sources. Takes IRQ to unbind from.
@@ -44,6 +57,14 @@ int bind_interdomain_evtchn_to_irqhandler(unsigned int remote_domain,
  */
 void unbind_from_irqhandler(unsigned int irq, void *dev_id);
 
+/*
+ * Send late EOI for an IRQ bound to an event channel via one of the *_lateeoi
+ * functions above.
+ */
+void xen_irq_lateeoi(unsigned int irq, unsigned int eoi_flags);
+/* Signal an event was spurious, i.e. there was no action resulting from it. */
+#define XEN_EOI_FLAG_SPURIOUS	0x00000001
+
 #define XEN_IRQ_PRIORITY_MAX     EVTCHN_FIFO_PRIORITY_MAX
 #define XEN_IRQ_PRIORITY_DEFAULT EVTCHN_FIFO_PRIORITY_DEFAULT
 #define XEN_IRQ_PRIORITY_MIN     EVTCHN_FIFO_PRIORITY_MIN