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Re: [PATCH] docs: Add '-device intel-iommu' entry

From: Jason Wang
Subject: Re: [PATCH] docs: Add '-device intel-iommu' entry
Date: Wed, 7 Jul 2021 11:35:43 +0800
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0

在 2021/6/12 上午2:55, Peter Xu 写道:
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>
Signed-off-by: Peter Xu <peterx@redhat.com>
  qemu-options.hx | 32 ++++++++++++++++++++++++++++++++
  1 file changed, 32 insertions(+)

diff --git a/qemu-options.hx b/qemu-options.hx
index 14258784b3a..4bb04243907 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -926,6 +926,38 @@ 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 in the guest.

I think we don't need "in the guest" here.

Other than this:

Reviewed-by: Jason Wang <jasowang@redhat.com>


  It's required
+        to enable complete x2apic.  Currently it only supports kvm
+        kernel-irqchip modes ``off`` or ``split``.  Full kernel-irqchip is not
+        yet supported.
+    ``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.
DEF("name", HAS_ARG, QEMU_OPTION_name,

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