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<h3>This Page</h3>
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<section id="vfio-virtual-device">
<h1>VFIO virtual device<a class="headerlink" href="#vfio-virtual-device" title="Link to this heading">ΒΆ</a></h1>
<p>Device types supported:</p>
<blockquote>
<div><ul class="simple">
<li><p>KVM_DEV_TYPE_VFIO</p></li>
</ul>
</div></blockquote>
<p>Only one VFIO instance may be created per VM. The created device
tracks VFIO files (group or device) in use by the VM and features
of those groups/devices important to the correctness and acceleration
of the VM. As groups/devices are enabled and disabled for use by the
VM, KVM should be updated about their presence. When registered with
KVM, a reference to the VFIO file is held by KVM.</p>
<dl>
<dt>Groups:</dt><dd><dl class="simple">
<dt>KVM_DEV_VFIO_FILE</dt><dd><p>alias: KVM_DEV_VFIO_GROUP</p>
</dd>
</dl>
</dd>
<dt>KVM_DEV_VFIO_FILE attributes:</dt><dd><dl>
<dt>KVM_DEV_VFIO_FILE_ADD: Add a VFIO file (group/device) to VFIO-KVM device</dt><dd><p>tracking</p>
<p>kvm_device_attr.addr points to an int32_t file descriptor for the
VFIO file.</p>
</dd>
<dt>KVM_DEV_VFIO_FILE_DEL: Remove a VFIO file (group/device) from VFIO-KVM</dt><dd><p>device tracking</p>
<p>kvm_device_attr.addr points to an int32_t file descriptor for the
VFIO file.</p>
</dd>
</dl>
</dd>
<dt>KVM_DEV_VFIO_GROUP (legacy kvm device group restricted to the handling of VFIO group fd):</dt><dd><p>KVM_DEV_VFIO_GROUP_ADD: same as KVM_DEV_VFIO_FILE_ADD for group fd only</p>
<p>KVM_DEV_VFIO_GROUP_DEL: same as KVM_DEV_VFIO_FILE_DEL for group fd only</p>
<dl>
<dt>KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE: attaches a guest visible TCE table</dt><dd><p>allocated by sPAPR KVM.
kvm_device_attr.addr points to a struct:</p>
<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>struct kvm_vfio_spapr_tce {
__s32 groupfd;
__s32 tablefd;
};
</pre></div>
</div>
<p>where:</p>
<ul class="simple">
<li><p>@groupfd is a file descriptor for a VFIO group;</p></li>
<li><p>@tablefd is a file descriptor for a TCE table allocated via
KVM_CREATE_SPAPR_TCE.</p></li>
</ul>
</dd>
</dl>
</dd>
</dl>
<p>The FILE/GROUP_ADD operation above should be invoked prior to accessing the
device file descriptor via VFIO_GROUP_GET_DEVICE_FD in order to support
drivers which require a kvm pointer to be set in their .<code class="xref c c-func broken_xref docutils literal notranslate"><span class="pre">open_device()</span></code>
callback. It is the same for device file descriptor via character device
open which gets device access via VFIO_DEVICE_BIND_IOMMUFD. For such file
descriptors, FILE_ADD should be invoked before VFIO_DEVICE_BIND_IOMMUFD
to support the drivers mentioned in prior sentence as well.</p>
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