xen: Port Xen event channel driver from mini-os

Make required updates to run on u-boot. Strip functionality
not needed by U-boot.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Anastasiia Lukianenko <anastasiia_lukianenko@epam.com>

drivers/xen/Makefile

@@ -3,3 +3,4 @@
 # (C) Copyright 2020 EPAM Systems Inc.
 
 obj-y += hypervisor.o
+obj-y += events.o

drivers/xen/events.c

@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * (C) 2003 - Rolf Neugebauer - Intel Research Cambridge
+ * (C) 2005 - Grzegorz Milos - Intel Research Cambridge
+ * (C) 2020 - EPAM Systems Inc.
+ *
+ * File: events.c [1]
+ * Author: Rolf Neugebauer (neugebar@dcs.gla.ac.uk)
+ * Changes: Grzegorz Milos (gm281@cam.ac.uk)
+ *
+ * Date: Jul 2003, changes Jun 2005
+ *
+ * Description: Deals with events received on event channels
+ *
+ * [1] - http://xenbits.xen.org/gitweb/?p=mini-os.git;a=summary
+ */
+#include <common.h>
+#include <log.h>
+
+#include <asm/io.h>
+#include <asm/xen/system.h>
+
+#include <xen/events.h>
+#include <xen/hvm.h>
+
+#define NR_EVS 1024
+
+/**
+ * struct _ev_action - represents a event handler.
+ *
+ * Chaining or sharing is not allowed
+ */
+struct _ev_action {
+	void (*handler)(evtchn_port_t port, struct pt_regs *regs, void *data);
+	void *data;
+	u32 count;
+};
+
+static struct _ev_action ev_actions[NR_EVS];
+void default_handler(evtchn_port_t port, struct pt_regs *regs, void *data);
+
+static unsigned long bound_ports[NR_EVS / (8 * sizeof(unsigned long))];
+
+void unbind_all_ports(void)
+{
+	int i;
+	int cpu = 0;
+	struct shared_info *s = HYPERVISOR_shared_info;
+	struct vcpu_info *vcpu_info = &s->vcpu_info[cpu];
+
+	for (i = 0; i < NR_EVS; i++) {
+		if (test_and_clear_bit(i, bound_ports)) {
+			printf("port %d still bound!\n", i);
+			unbind_evtchn(i);
+		}
+	}
+	vcpu_info->evtchn_upcall_pending = 0;
+	vcpu_info->evtchn_pending_sel = 0;
+}
+
+int do_event(evtchn_port_t port, struct pt_regs *regs)
+{
+	struct _ev_action *action;
+
+	clear_evtchn(port);
+
+	if (port >= NR_EVS) {
+		printk("WARN: do_event(): Port number too large: %d\n", port);
+		return 1;
+	}
+
+	action = &ev_actions[port];
+	action->count++;
+
+	/* call the handler */
+	action->handler(port, regs, action->data);
+
+	return 1;
+}
+
+evtchn_port_t bind_evtchn(evtchn_port_t port,
+			  void (*handler)(evtchn_port_t, struct pt_regs *, void *),
+			  void *data)
+{
+	if (ev_actions[port].handler != default_handler)
+		printf("WARN: Handler for port %d already registered, replacing\n",
+		       port);
+
+	ev_actions[port].data = data;
+	wmb();
+	ev_actions[port].handler = handler;
+	synch_set_bit(port, bound_ports);
+
+	return port;
+}
+
+/**
+ * unbind_evtchn() - Unbind event channel for selected port
+ */
+void unbind_evtchn(evtchn_port_t port)
+{
+	struct evtchn_close close;
+	int rc;
+
+	if (ev_actions[port].handler == default_handler)
+		printf("WARN: No handler for port %d when unbinding\n", port);
+	mask_evtchn(port);
+	clear_evtchn(port);
+
+	ev_actions[port].handler = default_handler;
+	wmb();
+	ev_actions[port].data = NULL;
+	synch_clear_bit(port, bound_ports);
+
+	close.port = port;
+	rc = HYPERVISOR_event_channel_op(EVTCHNOP_close, &close);
+	if (rc)
+		printf("WARN: close_port %d failed rc=%d. ignored\n", port, rc);
+}
+
+void default_handler(evtchn_port_t port, struct pt_regs *regs, void *ignore)
+{
+	debug("[Port %d] - event received\n", port);
+}
+
+/**
+ * evtchn_alloc_unbound() - Create a port available to the pal for
+ * exchanging notifications.
+ *
+ * Unfortunate confusion of terminology: the port is unbound as far
+ * as Xen is concerned, but we automatically bind a handler to it.
+ *
+ * Return: The result of the hypervisor call.
+ */
+int evtchn_alloc_unbound(domid_t pal,
+			 void (*handler)(evtchn_port_t, struct pt_regs *, void *),
+			 void *data, evtchn_port_t *port)
+{
+	int rc;
+
+	struct evtchn_alloc_unbound op;
+
+	op.dom = DOMID_SELF;
+	op.remote_dom = pal;
+	rc = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &op);
+	if (rc) {
+		printf("ERROR: alloc_unbound failed with rc=%d", rc);
+		return rc;
+	}
+	if (!handler)
+		handler = default_handler;
+	*port = bind_evtchn(op.port, handler, data);
+	return rc;
+}
+
+/**
+ * eventchn_poll() - Event channel polling function
+ *
+ * Check and process any pending events
+ */
+void eventchn_poll(void)
+{
+	do_hypervisor_callback(NULL);
+}
+
+/**
+ * init_events() - Initialize event handler
+ *
+ * Initially all events are without a handler and disabled.
+ */
+void init_events(void)
+{
+	int i;
+
+	debug("%s\n", __func__);
+
+	for (i = 0; i < NR_EVS; i++) {
+		ev_actions[i].handler = default_handler;
+		mask_evtchn(i);
+	}
+}
+
+/**
+ * fini_events() - Close all ports
+ *
+ * Mask and clear event channels. Close port using EVTCHNOP_close
+ * hypercall.
+ */
+void fini_events(void)
+{
+	debug("%s\n", __func__);
+	/* Dealloc all events */
+	unbind_all_ports();
+}
+

drivers/xen/hypervisor.c

@@ -20,6 +20,7 @@
 #include <linux/bug.h>
 
 #include <xen/hvm.h>
+#include <xen/events.h>
 #include <xen/interface/memory.h>
 
 #define active_evtchns(cpu, sh, idx)	\
@@ -163,9 +164,7 @@ void do_hypervisor_callback(struct pt_regs *regs)
 			l2 &= ~(1UL << l2i);
 
 			port = (l1i * (sizeof(unsigned long) * 8)) + l2i;
-			/* TODO: handle new event: do_event(port, regs); */
+			do_event(port, regs);
-			/* Suppress -Wunused-but-set-variable */
-			(void)(port);
 		}
 	}
 
@@ -236,5 +235,6 @@ void xen_init(void)
 	debug("%s\n", __func__);
 
 	map_shared_info(NULL);
+	init_events();
 }
 

include/xen.h

@@ -8,7 +8,7 @@
 /**
  * xen_init() - Xen initialization
  *
- * Map Xen memory pages.
+ * Map Xen memory pages, initialize event handler.
  */
 void xen_init(void);
 

include/xen/events.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * (C) 2003 - Rolf Neugebauer - Intel Research Cambridge
+ * (C) 2005 - Grzegorz Milos - Intel Reseach Cambridge
+ * (C) 2020 - EPAM Systems Inc.
+ *
+ * File: events.h
+ * Author: Rolf Neugebauer (neugebar@dcs.gla.ac.uk)
+ * Changes: Grzegorz Milos (gm281@cam.ac.uk)
+ *
+ * Date: Jul 2003, changes Jun 2005
+ *
+ * Description: Deals with events on the event channels
+ */
+#ifndef _EVENTS_H_
+#define _EVENTS_H_
+
+#include <asm/xen/hypercall.h>
+#include <xen/interface/event_channel.h>
+
+void init_events(void);
+void fini_events(void);
+
+int do_event(evtchn_port_t port, struct pt_regs *regs);
+void unbind_evtchn(evtchn_port_t port);
+void unbind_all_ports(void);
+int evtchn_alloc_unbound(domid_t pal,
+			 void (*handler)(evtchn_port_t, struct pt_regs *, void *),
+			 void *data, evtchn_port_t *port);
+
+/* Send notification via event channel */
+static inline int notify_remote_via_evtchn(evtchn_port_t port)
+{
+	struct evtchn_send op;
+
+	op.port = port;
+	return HYPERVISOR_event_channel_op(EVTCHNOP_send, &op);
+}
+
+void eventchn_poll(void);
+
+#endif /* _EVENTS_H_ */