[PATCH v4 4/4] qemu-options.hx: Add an entry for virtio-iommu-pci and document aw-bits

[Eric Auger <eric.auger@redhat.com>]

We are missing an entry for the virtio-iommu-pci device. Add the
information on which machine it is currently supported and document
the new aw-bits option.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 qemu-options.hx | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/qemu-options.hx b/qemu-options.hx
index 8547254dbf..6a8c970640 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1172,6 +1172,14 @@ SRST
     Please also refer to the wiki page for general scenarios of VT-d
     emulation in QEMU: https://wiki.qemu.org/Features/VT-d.
 
+``-device virtio-iommu-pci[,option=...]``
+    This is only supported by ``-machine q35`` and ``-machine virt``.
+    It supports below options:
+
+    ``aw-bits=val`` (val between 32 and 64, default depends on machine)
+        This decides the address width of IOVA address space. With
+        q35 it defaults to 39 bits. On arm virt it defaults to 48 bits.
+
 ERST
 
 DEF("name", HAS_ARG, QEMU_OPTION_name,
-- 
2.41.0