xen: Switch to libxenevtchn interface for compat shims.

In Xen 4.7 we are refactoring parts libxenctrl into a number of
separate libraries which will provide backward and forward API and ABI
compatiblity.

One such library will be libxenevtchn which provides access to event
channels.

In preparation for this switch the compatibility layer in xen_common.h
(which support building with older versions of Xen) to use what will
be the new library API. This means that the evtchn shim will disappear
for versions of Xen which include libxenevtchn.

To simplify things for the <= 4.0.0 support we wrap the int fd in a
malloc(sizeof int) such that the handle is always a pointer. This
leads to less typedef headaches and the need for
XC_HANDLER_INITIAL_VALUE etc for these interfaces.

Note that this patch does not add any support for actually using
libxenevtchn, it just adjusts the existing shims.

Note that xc_evtchn_alloc_unbound functionality remains in libxenctrl,
since that functionality is not exposed by /dev/xen/evtchn.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

hw/xen/xen_backend.c

@@ -243,19 +243,19 @@ static struct XenDevice *xen_be_get_xendev(const char *type, int dom, int dev,
     xendev->debug      = debug;
     xendev->local_port = -1;
 
-    xendev->evtchndev = xen_xc_evtchn_open(NULL, 0);
-    if (xendev->evtchndev == XC_HANDLER_INITIAL_VALUE) {
+    xendev->evtchndev = xenevtchn_open(NULL, 0);
+    if (xendev->evtchndev == NULL) {
         xen_be_printf(NULL, 0, "can't open evtchn device\n");
         g_free(xendev);
         return NULL;
     }
-    fcntl(xc_evtchn_fd(xendev->evtchndev), F_SETFD, FD_CLOEXEC);
+    fcntl(xenevtchn_fd(xendev->evtchndev), F_SETFD, FD_CLOEXEC);
 
     if (ops->flags & DEVOPS_FLAG_NEED_GNTDEV) {
         xendev->gnttabdev = xen_xc_gnttab_open(NULL, 0);
         if (xendev->gnttabdev == XC_HANDLER_INITIAL_VALUE) {
             xen_be_printf(NULL, 0, "can't open gnttab device\n");
-            xc_evtchn_close(xendev->evtchndev);
+            xenevtchn_close(xendev->evtchndev);
             g_free(xendev);
             return NULL;
         }
@@ -306,8 +306,8 @@ static struct XenDevice *xen_be_del_xendev(int dom, int dev)
             g_free(xendev->fe);
         }
 
-        if (xendev->evtchndev != XC_HANDLER_INITIAL_VALUE) {
-            xc_evtchn_close(xendev->evtchndev);
+        if (xendev->evtchndev != NULL) {
+            xenevtchn_close(xendev->evtchndev);
         }
         if (xendev->gnttabdev != XC_HANDLER_INITIAL_VALUE) {
             xc_gnttab_close(xendev->gnttabdev);
@@ -691,13 +691,14 @@ static void xen_be_evtchn_event(void *opaque)
     struct XenDevice *xendev = opaque;
     evtchn_port_t port;
 
-    port = xc_evtchn_pending(xendev->evtchndev);
+    port = xenevtchn_pending(xendev->evtchndev);
     if (port != xendev->local_port) {
-        xen_be_printf(xendev, 0, "xc_evtchn_pending returned %d (expected %d)\n",
+        xen_be_printf(xendev, 0,
+                      "xenevtchn_pending returned %d (expected %d)\n",
                       port, xendev->local_port);
         return;
     }
-    xc_evtchn_unmask(xendev->evtchndev, port);
+    xenevtchn_unmask(xendev->evtchndev, port);
 
     if (xendev->ops->event) {
         xendev->ops->event(xendev);
@@ -740,14 +741,14 @@ int xen_be_bind_evtchn(struct XenDevice *xendev)
     if (xendev->local_port != -1) {
         return 0;
     }
-    xendev->local_port = xc_evtchn_bind_interdomain
+    xendev->local_port = xenevtchn_bind_interdomain
         (xendev->evtchndev, xendev->dom, xendev->remote_port);
     if (xendev->local_port == -1) {
-        xen_be_printf(xendev, 0, "xc_evtchn_bind_interdomain failed\n");
+        xen_be_printf(xendev, 0, "xenevtchn_bind_interdomain failed\n");
         return -1;
     }
     xen_be_printf(xendev, 2, "bind evtchn port %d\n", xendev->local_port);
-    qemu_set_fd_handler(xc_evtchn_fd(xendev->evtchndev),
+    qemu_set_fd_handler(xenevtchn_fd(xendev->evtchndev),
                         xen_be_evtchn_event, NULL, xendev);
     return 0;
 }
@@ -757,15 +758,15 @@ void xen_be_unbind_evtchn(struct XenDevice *xendev)
     if (xendev->local_port == -1) {
         return;
     }
-    qemu_set_fd_handler(xc_evtchn_fd(xendev->evtchndev), NULL, NULL, NULL);
-    xc_evtchn_unbind(xendev->evtchndev, xendev->local_port);
+    qemu_set_fd_handler(xenevtchn_fd(xendev->evtchndev), NULL, NULL, NULL);
+    xenevtchn_unbind(xendev->evtchndev, xendev->local_port);
     xen_be_printf(xendev, 2, "unbind evtchn port %d\n", xendev->local_port);
     xendev->local_port = -1;
 }
 
 int xen_be_send_notify(struct XenDevice *xendev)
 {
-    return xc_evtchn_notify(xendev->evtchndev, xendev->local_port);
+    return xenevtchn_notify(xendev->evtchndev, xendev->local_port);
 }
 
 /*

include/hw/xen/xen_backend.h

@@ -46,7 +46,7 @@ struct XenDevice {
     int                remote_port;
     int                local_port;
 
-    XenEvtchn          evtchndev;
+    xenevtchn_handle   *evtchndev;
     XenGnttab          gnttabdev;
 
     struct XenDevOps   *ops;

include/hw/xen/xen_common.h

@@ -39,17 +39,38 @@ static inline void *xc_map_foreign_bulk(int xc_handle, uint32_t dom, int prot,
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 410
 
 typedef int XenXC;
-typedef int XenEvtchn;
+typedef int xenevtchn_handle;
 typedef int XenGnttab;
 
 #  define XC_INTERFACE_FMT "%i"
 #  define XC_HANDLER_INITIAL_VALUE    -1
 
-static inline XenEvtchn xen_xc_evtchn_open(void *logger,
-                                           unsigned int open_flags)
+static inline xenevtchn_handle *xenevtchn_open(void *logger,
+                                               unsigned int open_flags)
 {
-    return xc_evtchn_open();
+    xenevtchn_handle *h = malloc(sizeof(*h));
+    if (!h) {
+        return NULL;
+    }
+    *h = xc_evtchn_open();
+    if (*h == -1) {
+        free(h);
+        h = NULL;
+    }
+    return h;
 }
+static inline int xenevtchn_close(xenevtchn_handle *h)
+{
+    int rc = xc_evtchn_close(*h);
+    free(h);
+    return rc;
+}
+#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_unmask(*h, p)
 
 static inline XenGnttab xen_xc_gnttab_open(void *logger,
                                            unsigned int open_flags)
@@ -108,17 +129,20 @@ static inline void xs_close(struct xs_handle *xsh)
 #else
 
 typedef xc_interface *XenXC;
-typedef xc_evtchn *XenEvtchn;
+typedef xc_evtchn xenevtchn_handle;
 typedef xc_gnttab *XenGnttab;
 
 #  define XC_INTERFACE_FMT "%p"
 #  define XC_HANDLER_INITIAL_VALUE    NULL
 
-static inline XenEvtchn xen_xc_evtchn_open(void *logger,
-                                           unsigned int open_flags)
-{
-    return xc_evtchn_open(logger, open_flags);
-}
+#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)
 
 static inline XenGnttab xen_xc_gnttab_open(void *logger,
                                            unsigned int open_flags)

xen-hvm.c

@@ -110,7 +110,7 @@ typedef struct XenIOState {
     /* evtchn local port for buffered io */
     evtchn_port_t bufioreq_local_port;
     /* the evtchn fd for polling */
-    XenEvtchn xce_handle;
+    xenevtchn_handle *xce_handle;
     /* which vcpu we are serving */
     int send_vcpu;
 
@@ -717,7 +717,7 @@ static ioreq_t *cpu_get_ioreq(XenIOState *state)
     int i;
     evtchn_port_t port;
 
-    port = xc_evtchn_pending(state->xce_handle);
+    port = xenevtchn_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));
@@ -736,7 +736,7 @@ static ioreq_t *cpu_get_ioreq(XenIOState *state)
         }
 
         /* unmask the wanted port again */
-        xc_evtchn_unmask(state->xce_handle, port);
+        xenevtchn_unmask(state->xce_handle, port);
 
         /* get the io packet from shared memory */
         state->send_vcpu = i;
@@ -1043,7 +1043,7 @@ 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);
-        xc_evtchn_unmask(state->xce_handle, state->bufioreq_local_port);
+        xenevtchn_unmask(state->xce_handle, state->bufioreq_local_port);
     }
 }
 
@@ -1087,7 +1087,8 @@ static void cpu_handle_ioreq(void *opaque)
         }
 
         req->state = STATE_IORESP_READY;
-        xc_evtchn_notify(state->xce_handle, state->ioreq_local_port[state->send_vcpu]);
+        xenevtchn_notify(state->xce_handle,
+                         state->ioreq_local_port[state->send_vcpu]);
     }
 }
 
@@ -1095,8 +1096,8 @@ static void xen_main_loop_prepare(XenIOState *state)
 {
     int evtchn_fd = -1;
 
-    if (state->xce_handle != XC_HANDLER_INITIAL_VALUE) {
-        evtchn_fd = xc_evtchn_fd(state->xce_handle);
+    if (state->xce_handle != NULL) {
+        evtchn_fd = xenevtchn_fd(state->xce_handle);
     }
 
     state->buffered_io_timer = timer_new_ms(QEMU_CLOCK_REALTIME, handle_buffered_io,
@@ -1134,7 +1135,7 @@ static void xen_exit_notifier(Notifier *n, void *data)
 {
     XenIOState *state = container_of(n, XenIOState, exit);
 
-    xc_evtchn_close(state->xce_handle);
+    xenevtchn_close(state->xce_handle);
     xs_daemon_close(state->xenstore);
 }
 
@@ -1201,8 +1202,8 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
 
     state = g_malloc0(sizeof (XenIOState));
 
-    state->xce_handle = xen_xc_evtchn_open(NULL, 0);
-    if (state->xce_handle == XC_HANDLER_INITIAL_VALUE) {
+    state->xce_handle = xenevtchn_open(NULL, 0);
+    if (state->xce_handle == NULL) {
         perror("xen: event channel open");
         goto err;
     }
@@ -1289,7 +1290,7 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
 
     /* FIXME: how about if we overflow the page here? */
     for (i = 0; i < max_cpus; i++) {
-        rc = xc_evtchn_bind_interdomain(state->xce_handle, xen_domid,
+        rc = xenevtchn_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);
@@ -1298,7 +1299,7 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
         state->ioreq_local_port[i] = rc;
     }
 
-    rc = xc_evtchn_bind_interdomain(state->xce_handle, xen_domid,
+    rc = xenevtchn_bind_interdomain(state->xce_handle, xen_domid,
                                     bufioreq_evtchn);
     if (rc == -1) {
         error_report("buffered evtchn bind error %d", errno);