CA-202608: Trigger refresh after system resume

If the guest is suspended and then resumed or migrated, trigger a
refresh to repopulate the xenstore entries (since the guest will have a
new domid).

Without doing this, XAPI thinks that the guest does not have PV drivers
installed and will refuse to do a vbd-plug operation until then next
refresh by the guest agent.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>

1 files changed, 76 insertions, 0 deletions

diff --git a/system/system.go b/system/system.go
new file mode 100644
index 0000000..b21d000
--- /dev/null
+++ b/system/system.go
@@ -0,0 +1,76 @@
+package sys
+
+import (
+	"math"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+const (
+	CLOCK_REALTIME          = 0
+	TFD_CLOEXEC             = 02000000
+	TFD_TIMER_ABSTIME       = 1
+	TFD_TIMER_CANCEL_ON_SET = 2
+)
+
+type ITimerSpec struct {
+	Interval syscall.Timespec
+	Value    syscall.Timespec
+}
+
+// System call wrapper for timerfd_create, generated with mksyscall.pl
+func timerfdCreate(clockid int, flags int) (fd int, err error) {
+	r0, _, e1 := syscall.Syscall(syscall.SYS_TIMERFD_CREATE,
+		uintptr(clockid), uintptr(flags), 0)
+	fd = int(r0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+// System call wrapper for timerfd_settime, generated with mksyscall.pl
+func timerfdSettime(fd int, flags int, new_value *ITimerSpec,
+	old_value *ITimerSpec) (err error) {
+	_, _, e1 := syscall.Syscall6(syscall.SYS_TIMERFD_SETTIME, uintptr(fd),
+		uintptr(flags),
+		uintptr(unsafe.Pointer(new_value)),
+		uintptr(unsafe.Pointer(old_value)), 0, 0)
+	if e1 != 0 {
+		err = e1
+	}
+	return
+}
+
+/*
+ * Send a notification on @c when the system has just been resumed after
+ * sleep. This is implemented by watching for a change in real time compared
+ * with monotonic time. This may cause a spurious notification if the time
+ * is changed by a user or NTP jump.
+ */
+func NotifyResumed(c chan int) {
+	ts := ITimerSpec{Interval: syscall.Timespec{math.MaxInt32, 0},
+		Value: syscall.Timespec{0, 0}}
+	buf := make([]byte, 8)
+	for {
+		fd, err := timerfdCreate(CLOCK_REALTIME, TFD_CLOEXEC)
+		if err != nil {
+			return
+		}
+
+		err = timerfdSettime(fd, TFD_TIMER_ABSTIME|TFD_TIMER_CANCEL_ON_SET, &ts, nil)
+		if err != nil {
+			return
+		}
+
+		_, err = syscall.Read(fd, buf)
+		if err == syscall.ECANCELED {
+			// Wait a bit for the system to settle down after resuming
+			time.Sleep(time.Duration(1) * time.Second)
+			c <- 1
+		}
+
+		syscall.Close(fd)
+	}
+}