docs: Document virtio PCI -device ioeventfd=on|off

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/docs/qdev-device-use.txt b/docs/qdev-device-use.txt
index f252c8e3bc..f2f9b757a5 100644
--- a/docs/qdev-device-use.txt
+++ b/docs/qdev-device-use.txt
@@ -97,10 +97,13 @@ The -device argument differs in detail for each kind of drive:
 
 * if=virtio
 
-  -device virtio-blk-pci,drive=DRIVE-ID,class=C,vectors=V
+  -device virtio-blk-pci,drive=DRIVE-ID,class=C,vectors=V,ioeventfd=IOEVENTFD
 
   This lets you control PCI device class and MSI-X vectors.
 
+  IOEVENTFD controls whether or not ioeventfd is used for virtqueue notify.  It
+  can be set to on (default) or off.
+
   As for all PCI devices, you can add bus=PCI-BUS,addr=DEVFN to
   control the PCI device address.
 
@@ -240,6 +243,9 @@ For PCI devices, you can add bus=PCI-BUS,addr=DEVFN to control the PCI
 device address, as usual.  The old -net nic provides parameter addr
 for that, it is silently ignored when the NIC is not a PCI device.
 
+For virtio-net-pci, you can control whether or not ioeventfd is used for
+virtqueue notify by setting ioeventfd= to on or off (default).
+
 -net nic accepts vectors=V for all models, but it's silently ignored
 except for virtio-net-pci (model=virtio).  With -device, only devices
 that support it accept it.