hw/xen: Add evtchn operations to allow redirection to internal emulation

The existing implementation calling into the real libxenevtchn moves to
a new file hw/xen/xen-operations.c, and is called via a function table
which in a subsequent commit will also be able to invoke the emulated
event channel support.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

7 files changed, 120 insertions, 45 deletions

diff --git a/hw/9pfs/xen-9p-backend.c b/hw/9pfs/xen-9p-backend.c
index 65c4979..864bdaf 100644
--- a/hw/9pfs/xen-9p-backend.c
+++ b/hw/9pfs/xen-9p-backend.c
@@ -241,7 +241,7 @@ static void xen_9pfs_push_and_notify(V9fsPDU *pdu)
     xen_wmb();
 
     ring->inprogress = false;
-    xenevtchn_notify(ring->evtchndev, ring->local_port);
+    qemu_xen_evtchn_notify(ring->evtchndev, ring->local_port);
 
     qemu_bh_schedule(ring->bh);
 }
@@ -324,8 +324,8 @@ static void xen_9pfs_evtchn_event(void *opaque)
     Xen9pfsRing *ring = opaque;
     evtchn_port_t port;
 
-    port = xenevtchn_pending(ring->evtchndev);
-    xenevtchn_unmask(ring->evtchndev, port);
+    port = qemu_xen_evtchn_pending(ring->evtchndev);
+    qemu_xen_evtchn_unmask(ring->evtchndev, port);
 
     qemu_bh_schedule(ring->bh);
 }
@@ -337,10 +337,10 @@ static void xen_9pfs_disconnect(struct XenLegacyDevice *xendev)
 
     for (i = 0; i < xen_9pdev->num_rings; i++) {
         if (xen_9pdev->rings[i].evtchndev != NULL) {
-            qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
-                    NULL, NULL, NULL);
-            xenevtchn_unbind(xen_9pdev->rings[i].evtchndev,
-                             xen_9pdev->rings[i].local_port);
+            qemu_set_fd_handler(qemu_xen_evtchn_fd(xen_9pdev->rings[i].evtchndev),
+                                NULL, NULL, NULL);
+            qemu_xen_evtchn_unbind(xen_9pdev->rings[i].evtchndev,
+                                   xen_9pdev->rings[i].local_port);
             xen_9pdev->rings[i].evtchndev = NULL;
         }
     }
@@ -447,12 +447,12 @@ static int xen_9pfs_connect(struct XenLegacyDevice *xendev)
         xen_9pdev->rings[i].inprogress = false;
 
 
-        xen_9pdev->rings[i].evtchndev = xenevtchn_open(NULL, 0);
+        xen_9pdev->rings[i].evtchndev = qemu_xen_evtchn_open();
         if (xen_9pdev->rings[i].evtchndev == NULL) {
             goto out;
         }
-        qemu_set_cloexec(xenevtchn_fd(xen_9pdev->rings[i].evtchndev));
-        xen_9pdev->rings[i].local_port = xenevtchn_bind_interdomain
+        qemu_set_cloexec(qemu_xen_evtchn_fd(xen_9pdev->rings[i].evtchndev));
+        xen_9pdev->rings[i].local_port = qemu_xen_evtchn_bind_interdomain
                                             (xen_9pdev->rings[i].evtchndev,
                                              xendev->dom,
                                              xen_9pdev->rings[i].evtchn);
@@ -463,8 +463,8 @@ static int xen_9pfs_connect(struct XenLegacyDevice *xendev)
             goto out;
         }
         xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
-        qemu_set_fd_handler(xenevtchn_fd(xen_9pdev->rings[i].evtchndev),
-                xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
+        qemu_set_fd_handler(qemu_xen_evtchn_fd(xen_9pdev->rings[i].evtchndev),
+                            xen_9pfs_evtchn_event, NULL, &xen_9pdev->rings[i]);
     }
 
     xen_9pdev->security_model = xenstore_read_be_str(xendev, "security_model");
diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index e5a1dd1..cb1d24f 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -761,7 +761,7 @@ static ioreq_t *cpu_get_ioreq(XenIOState *state)
     int i;
     evtchn_port_t port;
 
-    port = xenevtchn_pending(state->xce_handle);
+    port = qemu_xen_evtchn_pending(state->xce_handle);
     if (port == state->bufioreq_local_port) {
         timer_mod(state->buffered_io_timer,
                 BUFFER_IO_MAX_DELAY + qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
@@ -780,7 +780,7 @@ static ioreq_t *cpu_get_ioreq(XenIOState *state)
         }
 
         /* unmask the wanted port again */
-        xenevtchn_unmask(state->xce_handle, port);
+        qemu_xen_evtchn_unmask(state->xce_handle, port);
 
         /* get the io packet from shared memory */
         state->send_vcpu = i;
@@ -1147,7 +1147,7 @@ static void handle_buffered_io(void *opaque)
                 BUFFER_IO_MAX_DELAY + qemu_clock_get_ms(QEMU_CLOCK_REALTIME));
     } else {
         timer_del(state->buffered_io_timer);
-        xenevtchn_unmask(state->xce_handle, state->bufioreq_local_port);
+        qemu_xen_evtchn_unmask(state->xce_handle, state->bufioreq_local_port);
     }
 }
 
@@ -1196,8 +1196,8 @@ static void cpu_handle_ioreq(void *opaque)
         }
 
         req->state = STATE_IORESP_READY;
-        xenevtchn_notify(state->xce_handle,
-                         state->ioreq_local_port[state->send_vcpu]);
+        qemu_xen_evtchn_notify(state->xce_handle,
+                               state->ioreq_local_port[state->send_vcpu]);
     }
 }
 
@@ -1206,7 +1206,7 @@ static void xen_main_loop_prepare(XenIOState *state)
     int evtchn_fd = -1;
 
     if (state->xce_handle != NULL) {
-        evtchn_fd = xenevtchn_fd(state->xce_handle);
+        evtchn_fd = qemu_xen_evtchn_fd(state->xce_handle);
     }
 
     state->buffered_io_timer = timer_new_ms(QEMU_CLOCK_REALTIME, handle_buffered_io,
@@ -1249,7 +1249,7 @@ static void xen_exit_notifier(Notifier *n, void *data)
         xenforeignmemory_unmap_resource(xen_fmem, state->fres);
     }
 
-    xenevtchn_close(state->xce_handle);
+    qemu_xen_evtchn_close(state->xce_handle);
     xs_daemon_close(state->xenstore);
 }
 
@@ -1397,9 +1397,11 @@ void xen_hvm_init_pc(PCMachineState *pcms, MemoryRegion **ram_memory)
     xen_pfn_t ioreq_pfn;
     XenIOState *state;
 
+    setup_xen_backend_ops();
+
     state = g_new0(XenIOState, 1);
 
-    state->xce_handle = xenevtchn_open(NULL, 0);
+    state->xce_handle = qemu_xen_evtchn_open();
     if (state->xce_handle == NULL) {
         perror("xen: event channel open");
         goto err;
@@ -1463,8 +1465,9 @@ void xen_hvm_init_pc(PCMachineState *pcms, MemoryRegion **ram_memory)
 
     /* FIXME: how about if we overflow the page here? */
     for (i = 0; i < max_cpus; i++) {
-        rc = xenevtchn_bind_interdomain(state->xce_handle, xen_domid,
-                                        xen_vcpu_eport(state->shared_page, i));
+        rc = qemu_xen_evtchn_bind_interdomain(state->xce_handle, xen_domid,
+                                              xen_vcpu_eport(state->shared_page,
+                                                             i));
         if (rc == -1) {
             error_report("shared evtchn %d bind error %d", i, errno);
             goto err;
@@ -1472,8 +1475,8 @@ void xen_hvm_init_pc(PCMachineState *pcms, MemoryRegion **ram_memory)
         state->ioreq_local_port[i] = rc;
     }
 
-    rc = xenevtchn_bind_interdomain(state->xce_handle, xen_domid,
-                                    state->bufioreq_remote_port);
+    rc = qemu_xen_evtchn_bind_interdomain(state->xce_handle, xen_domid,
+                                          state->bufioreq_remote_port);
     if (rc == -1) {
         error_report("buffered evtchn bind error %d", errno);
         goto err;
diff --git a/hw/xen/meson.build b/hw/xen/meson.build
index ae0ace3..f195bbd 100644
--- a/hw/xen/meson.build
+++ b/hw/xen/meson.build
@@ -5,6 +5,7 @@ softmmu_ss.add(when: ['CONFIG_XEN', xen], if_true: files(
   'xen-legacy-backend.c',
   'xen_devconfig.c',
   'xen_pvdev.c',
+  'xen-operations.c',
 ))
 
 xen_specific_ss = ss.source_set()
diff --git a/hw/xen/xen-bus.c b/hw/xen/xen-bus.c
index df3f6b9..d0b1ae9 100644
--- a/hw/xen/xen-bus.c
+++ b/hw/xen/xen-bus.c
@@ -1095,12 +1095,12 @@ static bool xen_device_poll(void *opaque)
 static void xen_device_event(void *opaque)
 {
     XenEventChannel *channel = opaque;
-    unsigned long port = xenevtchn_pending(channel->xeh);
+    unsigned long port = qemu_xen_evtchn_pending(channel->xeh);
 
     if (port == channel->local_port) {
         xen_device_poll(channel);
 
-        xenevtchn_unmask(channel->xeh, port);
+        qemu_xen_evtchn_unmask(channel->xeh, port);
     }
 }
 
@@ -1115,11 +1115,11 @@ void xen_device_set_event_channel_context(XenDevice *xendev,
     }
 
     if (channel->ctx)
-        aio_set_fd_handler(channel->ctx, xenevtchn_fd(channel->xeh), true,
+        aio_set_fd_handler(channel->ctx, qemu_xen_evtchn_fd(channel->xeh), true,
                            NULL, NULL, NULL, NULL, NULL);
 
     channel->ctx = ctx;
-    aio_set_fd_handler(channel->ctx, xenevtchn_fd(channel->xeh), true,
+    aio_set_fd_handler(channel->ctx, qemu_xen_evtchn_fd(channel->xeh), true,
                        xen_device_event, NULL, xen_device_poll, NULL, channel);
 }
 
@@ -1131,13 +1131,13 @@ XenEventChannel *xen_device_bind_event_channel(XenDevice *xendev,
     XenEventChannel *channel = g_new0(XenEventChannel, 1);
     xenevtchn_port_or_error_t local_port;
 
-    channel->xeh = xenevtchn_open(NULL, 0);
+    channel->xeh = qemu_xen_evtchn_open();
     if (!channel->xeh) {
         error_setg_errno(errp, errno, "failed xenevtchn_open");
         goto fail;
     }
 
-    local_port = xenevtchn_bind_interdomain(channel->xeh,
+    local_port = qemu_xen_evtchn_bind_interdomain(channel->xeh,
                                             xendev->frontend_id,
                                             port);
     if (local_port < 0) {
@@ -1160,7 +1160,7 @@ XenEventChannel *xen_device_bind_event_channel(XenDevice *xendev,
 
 fail:
     if (channel->xeh) {
-        xenevtchn_close(channel->xeh);
+        qemu_xen_evtchn_close(channel->xeh);
     }
 
     g_free(channel);
@@ -1177,7 +1177,7 @@ void xen_device_notify_event_channel(XenDevice *xendev,
         return;
     }
 
-    if (xenevtchn_notify(channel->xeh, channel->local_port) < 0) {
+    if (qemu_xen_evtchn_notify(channel->xeh, channel->local_port) < 0) {
         error_setg_errno(errp, errno, "xenevtchn_notify failed");
     }
 }
@@ -1193,14 +1193,14 @@ void xen_device_unbind_event_channel(XenDevice *xendev,
 
     QLIST_REMOVE(channel, list);
 
-    aio_set_fd_handler(channel->ctx, xenevtchn_fd(channel->xeh), true,
+    aio_set_fd_handler(channel->ctx, qemu_xen_evtchn_fd(channel->xeh), true,
                        NULL, NULL, NULL, NULL, NULL);
 
-    if (xenevtchn_unbind(channel->xeh, channel->local_port) < 0) {
+    if (qemu_xen_evtchn_unbind(channel->xeh, channel->local_port) < 0) {
         error_setg_errno(errp, errno, "xenevtchn_unbind failed");
     }
 
-    xenevtchn_close(channel->xeh);
+    qemu_xen_evtchn_close(channel->xeh);
     g_free(channel);
 }
 
diff --git a/hw/xen/xen-legacy-backend.c b/hw/xen/xen-legacy-backend.c
index afba71f..9ce3dc2 100644
--- a/hw/xen/xen-legacy-backend.c
+++ b/hw/xen/xen-legacy-backend.c
@@ -294,13 +294,13 @@ static struct XenLegacyDevice *xen_be_get_xendev(const char *type, int dom,
     xendev->debug      = debug;
     xendev->local_port = -1;
 
-    xendev->evtchndev = xenevtchn_open(NULL, 0);
+    xendev->evtchndev = qemu_xen_evtchn_open();
     if (xendev->evtchndev == NULL) {
         xen_pv_printf(NULL, 0, "can't open evtchn device\n");
         qdev_unplug(DEVICE(xendev), NULL);
         return NULL;
     }
-    qemu_set_cloexec(xenevtchn_fd(xendev->evtchndev));
+    qemu_set_cloexec(qemu_xen_evtchn_fd(xendev->evtchndev));
 
     xen_pv_insert_xendev(xendev);
 
@@ -751,14 +751,14 @@ int xen_be_bind_evtchn(struct XenLegacyDevice *xendev)
     if (xendev->local_port != -1) {
         return 0;
     }
-    xendev->local_port = xenevtchn_bind_interdomain
+    xendev->local_port = qemu_xen_evtchn_bind_interdomain
         (xendev->evtchndev, xendev->dom, xendev->remote_port);
     if (xendev->local_port == -1) {
         xen_pv_printf(xendev, 0, "xenevtchn_bind_interdomain failed\n");
         return -1;
     }
     xen_pv_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
-    qemu_set_fd_handler(xenevtchn_fd(xendev->evtchndev),
+    qemu_set_fd_handler(qemu_xen_evtchn_fd(xendev->evtchndev),
                         xen_pv_evtchn_event, NULL, xendev);
     return 0;
 }
diff --git a/hw/xen/xen-operations.c b/hw/xen/xen-operations.c
new file mode 100644
index 0000000..1a959d8
--- /dev/null
+++ b/hw/xen/xen-operations.c
@@ -0,0 +1,71 @@
+/*
+ * QEMU Xen backend support: Operations for true Xen
+ *
+ * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Authors: David Woodhouse <dwmw2@infradead.org>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+
+#include "hw/xen/xen_backend_ops.h"
+#include "hw/xen/xen_common.h"
+
+/*
+ * If we have new enough libxenctrl then we do not want/need these compat
+ * interfaces, despite what the user supplied cflags might say. They
+ * must be undefined before including xenctrl.h
+ */
+#undef XC_WANT_COMPAT_EVTCHN_API
+
+#include <xenctrl.h>
+
+/*
+ * We don't support Xen prior to 4.2.0.
+ */
+
+/* Xen 4.2 through 4.6 */
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40701
+
+typedef xc_evtchn xenevtchn_handle;
+typedef evtchn_port_or_error_t xenevtchn_port_or_error_t;
+
+#define xenevtchn_open(l, f) xc_evtchn_open(l, f);
+#define xenevtchn_close(h) xc_evtchn_close(h)
+#define xenevtchn_fd(h) xc_evtchn_fd(h)
+#define xenevtchn_pending(h) xc_evtchn_pending(h)
+#define xenevtchn_notify(h, p) xc_evtchn_notify(h, p)
+#define xenevtchn_bind_interdomain(h, d, p) xc_evtchn_bind_interdomain(h, d, p)
+#define xenevtchn_unmask(h, p) xc_evtchn_unmask(h, p)
+#define xenevtchn_unbind(h, p) xc_evtchn_unbind(h, p)
+
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40701 */
+
+#include <xenevtchn.h>
+
+#endif
+
+static xenevtchn_handle *libxenevtchn_backend_open(void)
+{
+    return xenevtchn_open(NULL, 0);
+}
+
+struct evtchn_backend_ops libxenevtchn_backend_ops = {
+    .open = libxenevtchn_backend_open,
+    .close = xenevtchn_close,
+    .bind_interdomain = xenevtchn_bind_interdomain,
+    .unbind = xenevtchn_unbind,
+    .get_fd = xenevtchn_fd,
+    .notify = xenevtchn_notify,
+    .unmask = xenevtchn_unmask,
+    .pending = xenevtchn_pending,
+};
+
+void setup_xen_backend_ops(void)
+{
+    xen_evtchn_ops = &libxenevtchn_backend_ops;
+}
diff --git a/hw/xen/xen_pvdev.c b/hw/xen/xen_pvdev.c
index 1a5177b..86a2c8e 100644
--- a/hw/xen/xen_pvdev.c
+++ b/hw/xen/xen_pvdev.c
@@ -238,14 +238,14 @@ void xen_pv_evtchn_event(void *opaque)
     struct XenLegacyDevice *xendev = opaque;
     evtchn_port_t port;
 
-    port = xenevtchn_pending(xendev->evtchndev);
+    port = qemu_xen_evtchn_pending(xendev->evtchndev);
     if (port != xendev->local_port) {
         xen_pv_printf(xendev, 0,
                       "xenevtchn_pending returned %d (expected %d)\n",
                       port, xendev->local_port);
         return;
     }
-    xenevtchn_unmask(xendev->evtchndev, port);
+    qemu_xen_evtchn_unmask(xendev->evtchndev, port);
 
     if (xendev->ops->event) {
         xendev->ops->event(xendev);
@@ -257,15 +257,15 @@ void xen_pv_unbind_evtchn(struct XenLegacyDevice *xendev)
     if (xendev->local_port == -1) {
         return;
     }
-    qemu_set_fd_handler(xenevtchn_fd(xendev->evtchndev), NULL, NULL, NULL);
-    xenevtchn_unbind(xendev->evtchndev, xendev->local_port);
+    qemu_set_fd_handler(qemu_xen_evtchn_fd(xendev->evtchndev), NULL, NULL, NULL);
+    qemu_xen_evtchn_unbind(xendev->evtchndev, xendev->local_port);
     xen_pv_printf(xendev, 2, "unbind evtchn port %d\n", xendev->local_port);
     xendev->local_port = -1;
 }
 
 int xen_pv_send_notify(struct XenLegacyDevice *xendev)
 {
-    return xenevtchn_notify(xendev->evtchndev, xendev->local_port);
+    return qemu_xen_evtchn_notify(xendev->evtchndev, xendev->local_port);
 }
 
 /* ------------------------------------------------------------- */
@@ -306,7 +306,7 @@ void xen_pv_del_xendev(struct XenLegacyDevice *xendev)
     }
 
     if (xendev->evtchndev != NULL) {
-        xenevtchn_close(xendev->evtchndev);
+        qemu_xen_evtchn_close(xendev->evtchndev);
     }
     if (xendev->gnttabdev != NULL) {
         xengnttab_close(xendev->gnttabdev);