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 <m...@redhat.com> --- Makefile.target | 1 + hw/event_notifier.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++++ hw/event_notifier.h | 16 +++++++++++++ qemu-common.h | 1 + 4 files changed, 80 insertions(+), 0 deletions(-) create mode 100644 hw/event_notifier.c create mode 100644 hw/event_notifier.h diff --git a/Makefile.target b/Makefile.target index ab3c438..004a703 100644 --- a/Makefile.target +++ b/Makefile.target @@ -175,6 +175,7 @@ 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 += event_notifier.o obj-y += rwhandler.o obj-$(CONFIG_KVM) += kvm.o kvm-all.o obj-$(CONFIG_ISA_MMIO) += isa_mmio.o diff --git a/hw/event_notifier.c b/hw/event_notifier.c new file mode 100644 index 0000000..13f3656 --- /dev/null +++ b/hw/event_notifier.c @@ -0,0 +1,62 @@ +/* + * event notifier support + * + * Copyright Red Hat, Inc. 2010 + * + * Authors: + * Michael S. Tsirkin <m...@redhat.com> + * + * This work is licensed under the terms of the GNU GPL, version 2. See + * the COPYING file in the top-level directory. + */ + +#include "hw.h" +#include "event_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/event_notifier.h b/hw/event_notifier.h new file mode 100644 index 0000000..24117ea --- /dev/null +++ b/hw/event_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 805be1a..f12a8f5 100644 --- a/qemu-common.h +++ b/qemu-common.h @@ -227,6 +227,7 @@ typedef struct uWireSlave uWireSlave; typedef struct I2SCodec I2SCodec; typedef struct DeviceState DeviceState; typedef struct SSIBus SSIBus; +typedef struct EventNotifier EventNotifier; typedef uint64_t pcibus_t; -- 1.7.0.18.g0d53a5