aio / timers: add ppoll support with qemu_poll_ns

Add qemu_poll_ns which works like g_poll but takes a nanosecond
timeout.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

configure

@@ -2818,6 +2818,22 @@ if compile_prog "" "" ; then
   dup3=yes
 fi
 
+# check for ppoll support
+ppoll=no
+cat > $TMPC << EOF
+#include <poll.h>
+
+int main(void)
+{
+    struct pollfd pfd = { .fd = 0, .events = 0, .revents = 0 };
+    ppoll(&pfd, 1, 0, 0);
+    return 0;
+}
+EOF
+if compile_prog "" "" ; then
+  ppoll=yes
+fi
+
 # check for epoll support
 epoll=no
 cat > $TMPC << EOF
@@ -3814,6 +3830,9 @@ fi
 if test "$dup3" = "yes" ; then
   echo "CONFIG_DUP3=y" >> $config_host_mak
 fi
+if test "$ppoll" = "yes" ; then
+  echo "CONFIG_PPOLL=y" >> $config_host_mak
+fi
 if test "$epoll" = "yes" ; then
   echo "CONFIG_EPOLL=y" >> $config_host_mak
 fi

include/qemu/timer.h

@@ -63,6 +63,18 @@ int64_t qemu_clock_deadline_ns(QEMUClock *clock);
  */
 int qemu_timeout_ns_to_ms(int64_t ns);
 
+/**
+ * qemu_poll_ns:
+ * @fds: Array of file descriptors
+ * @nfds: number of file descriptors
+ * @timeout: timeout in nanoseconds
+ *
+ * Perform a poll like g_poll but with a timeout in nanoseconds.
+ * See g_poll documentation for further details.
+ *
+ * Returns: number of fds ready
+ */
+int qemu_poll_ns(GPollFD *fds, guint nfds, int64_t timeout);
 void qemu_clock_enable(QEMUClock *clock, bool enabled);
 void qemu_clock_warp(QEMUClock *clock);
 

qemu-timer.c

@@ -37,6 +37,10 @@
 #include <mmsystem.h>
 #endif
 
+#ifdef CONFIG_PPOLL
+#include <poll.h>
+#endif
+
 /***********************************************************/
 /* timers */
 
@@ -323,6 +327,26 @@ int qemu_timeout_ns_to_ms(int64_t ns)
 }
 
 
+/* qemu implementation of g_poll which uses a nanosecond timeout but is
+ * otherwise identical to g_poll
+ */
+int qemu_poll_ns(GPollFD *fds, guint nfds, int64_t timeout)
+{
+#ifdef CONFIG_PPOLL
+    if (timeout < 0) {
+        return ppoll((struct pollfd *)fds, nfds, NULL, NULL);
+    } else {
+        struct timespec ts;
+        ts.tv_sec = timeout / 1000000000LL;
+        ts.tv_nsec = timeout % 1000000000LL;
+        return ppoll((struct pollfd *)fds, nfds, &ts, NULL);
+    }
+#else
+    return g_poll(fds, nfds, qemu_timeout_ns_to_ms(timeout));
+#endif
+}
+
+
 QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
                           QEMUTimerCB *cb, void *opaque)
 {