event notifiers are slightly generalized eventfd descriptors. Current
implementation depends on eventfd because vhost is the only user, and
vhost depends on eventfd anyway, but a stub is provided for non-eventfd
case.
We'll be able to further generalize this when another user comes along
and we see how to best do this.
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
Makefile.target | 1 +
hw/notifier.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
hw/notifier.h | 16 ++++++++++++++++
qemu-common.h | 1 +
4 files changed, 68 insertions(+), 0 deletions(-)
create mode 100644 hw/notifier.c
create mode 100644 hw/notifier.h
diff --git a/Makefile.target b/Makefile.target
index 0ddd2a0..7df9535 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -183,6 +183,7 @@ obj-y = vl.o async.o monitor.o pci.o pci_host.o pcie_host.o machine.o gdbstub.o
# virtio has to be here due to weird dependency between PCI and virtio-net.
# need to fix this properly
obj-y += virtio-blk.o virtio-balloon.o virtio-net.o virtio-pci.o virtio-serial-bus.o
+obj-y += notifier.o
obj-$(CONFIG_KVM) += kvm.o kvm-all.o
# MSI-X depends on kvm for interrupt injection,
# so moved it from Makefile.objs to Makefile.target for now
diff --git a/hw/notifier.c b/hw/notifier.c
new file mode 100644
index 0000000..dff38de
--- /dev/null
+++ b/hw/notifier.c
@@ -0,0 +1,50 @@
+#include "hw.h"
+#include "notifier.h"
+#ifdef CONFIG_EVENTFD
+#include <sys/eventfd.h>
+#endif
+
+int event_notifier_init(EventNotifier *e, int active)
+{
+#ifdef CONFIG_EVENTFD
+ int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
+ if (fd < 0)
+ return -errno;
+ e->fd = fd;
+ return 0;
+#else
+ return -ENOSYS;
+#endif
+}
+
+void event_notifier_cleanup(EventNotifier *e)
+{
+ close(e->fd);
+}
+
+int event_notifier_get_fd(EventNotifier *e)
+{
+ return e->fd;
+}
+
+int event_notifier_test_and_clear(EventNotifier *e)
+{
+ uint64_t value;
+ int r = read(e->fd, &value, sizeof value);
+ return r == sizeof value;
+}
+
+int event_notifier_test(EventNotifier *e)
+{
+ uint64_t value;
+ int r = read(e->fd, &value, sizeof value);
+ if (r == sizeof value) {
+ /* restore previous value. */
+ int s = write(e->fd, &value, sizeof value);
+ /* never blocks because we use EFD_SEMAPHORE.
+ * If we didn't we'd get EAGAIN on overflow
+ * and we'd have to write code to ignore it. */
+ assert(s == sizeof value);
+ }
+ return r == sizeof value;
+}
diff --git a/hw/notifier.h b/hw/notifier.h
new file mode 100644
index 0000000..24117ea
--- /dev/null
+++ b/hw/notifier.h
@@ -0,0 +1,16 @@
+#ifndef QEMU_EVENT_NOTIFIER_H
+#define QEMU_EVENT_NOTIFIER_H
+
+#include "qemu-common.h"
+
+struct EventNotifier {
+ int fd;
+};
+
+int event_notifier_init(EventNotifier *, int active);
+void event_notifier_cleanup(EventNotifier *);
+int event_notifier_get_fd(EventNotifier *);
+int event_notifier_test_and_clear(EventNotifier *);
+int event_notifier_test(EventNotifier *);
+
+#endif
diff --git a/qemu-common.h b/qemu-common.h
index bf14a22..5e935d1 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -224,6 +224,7 @@ typedef struct uWireSlave uWireSlave;
typedef struct I2SCodec I2SCodec;
typedef struct DeviceState DeviceState;
typedef struct SSIBus SSIBus;
+typedef struct EventNotifier EventNotifier;
/* CPU save/load. */
void cpu_save(QEMUFile *f, void *opaque);
--
1.6.6.144.g5c3af
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
