memory: emulate ioeventfd
The ioeventfd mechanism is used by vhost, dataplane, and virtio-pci to
turn guest MMIO/PIO writes into eventfd file descriptor events. This
allows arbitrary threads to be notified when the guest writes to a
specific MMIO/PIO address.
qtest and TCG do not support ioeventfd because memory writes are not
checked against registered ioeventfds in QEMU. This patch implements
this in memory_region_dispatch_write() so qtest can use ioeventfd.
Also this patch fixes vhost aborting on some misconfigured old kernels
like 3.18.0 on ARM. It is possible to explicitly enable CONFIG_EVENTFD
in expert settings, while MMIO binding support in KVM will still be
missing.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Pavel Fedin <p.fedin@samsung.com>
Message-Id: <006e01d12377$0b9c2d40$22d487c0$@samsung.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/kvm-all.c b/kvm-all.c
index a45c92b..ed707fe 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1628,8 +1628,10 @@
kvm_state = s;
- s->memory_listener.listener.eventfd_add = kvm_mem_ioeventfd_add;
- s->memory_listener.listener.eventfd_del = kvm_mem_ioeventfd_del;
+ if (kvm_eventfds_allowed) {
+ s->memory_listener.listener.eventfd_add = kvm_mem_ioeventfd_add;
+ s->memory_listener.listener.eventfd_del = kvm_mem_ioeventfd_del;
+ }
s->memory_listener.listener.coalesced_mmio_add = kvm_coalesce_mmio_region;
s->memory_listener.listener.coalesced_mmio_del = kvm_uncoalesce_mmio_region;
