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docs: Add '-device intel-iommu' entry 

The parameters of intel-iommu device are non-trivial to understand.  Add an
entry for it so that people can reference to it when using.

There're actually a few more options there, but I hide them explicitly because
they shouldn't be used by normal QEMU users.

Cc: Chao Yang <chayang@redhat.com>
Cc: Lei Yang <leiyang@redhat.com>
Cc: Jing Zhao <jinzhao@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210707154114.197580-1-peterx@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Peter Xu 2021-07-07 11:41:14 -04:00 committed by Michael S. Tsirkin
parent 538bb6f121
commit 7395b3e3e7
1 changed files with 33 additions and 0 deletions
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33
qemu-options.hx
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@ -939,6 +939,39 @@ SRST
``-device pci-ipmi-bt,bmc=id``
Like the KCS interface, but defines a BT interface on the PCI bus.
``-device intel-iommu[,option=...]``
This is only supported by ``-machine q35``, which will enable Intel VT-d
emulation within the guest. It supports below options:
``intremap=on|off`` (default: auto)
This enables interrupt remapping feature. It's required to enable
complete x2apic. Currently it only supports kvm kernel-irqchip modes
``off`` or ``split``, while full kernel-irqchip is not yet supported.
The default value is "auto", which will be decided by the mode of
kernel-irqchip.
``caching-mode=on|off`` (default: off)
This enables caching mode for the VT-d emulated device. When
caching-mode is enabled, each guest DMA buffer mapping will generate an
IOTLB invalidation from the guest IOMMU driver to the vIOMMU device in
a synchronous way. It is required for ``-device vfio-pci`` to work
with the VT-d device, because host assigned devices requires to setup
the DMA mapping on the host before guest DMA starts.
``device-iotlb=on|off`` (default: off)
This enables device-iotlb capability for the emulated VT-d device. So
far virtio/vhost should be the only real user for this parameter,
paired with ats=on configured for the device.
``aw-bits=39|48`` (default: 39)
This decides the address width of IOVA address space. The address
space has 39 bits width for 3-level IOMMU page tables, and 48 bits for
4-level IOMMU page tables.
Please also refer to the wiki page for general scenarios of VT-d
emulation in QEMU: https://wiki.qemu.org/Features/VT-d.
ERST
DEF("name", HAS_ARG, QEMU_OPTION_name,