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Re: [libvirt] [PATCH 1/2] conf: add eim attribute to <iommu><driver>



On Thu, 2017-05-18 at 11:09 +0200, Ján Tomko wrote:
> Add an attribute to control extended interrupt mode.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1451282

[...]
> @@ -7436,6 +7436,16 @@ qemu-kvm -net nic,model=? /dev/null
>                <span class="since">Since 3.4.0</span> (QEMU/KVM only)
>              </p>
>            </dd>
> +          <dt><code>eim</code></dt>
> +          <dd>
> +            <p>
> +              The <code>eim</code> attribute with possible values
> +              <code>on</code> and <code>off</code> can be used to
> +              turn on extended interrupt mode. In combination with intremap
> +              and split I/O APIC, this allows for more vCPUs to be used.
> +              <span class="since">Since 3.4.0</span> (QEMU/KVM only)
> +            </p>
> +          </dd>
>          </dl>
>        </dd>
>      </dl>

Actually, the documentation could use some work too.

How about:

  The <code>eim</code> attribute (with possible values
  <code>on</code> and <code>off</code>) can be used to
  configure Extended Interrupt Mode. A q35 domain with
  split I/O APIC (as described in
  <a href="#elementsFeatures">hypervisor features</a>),
  and both interrupt remapping and EIM turned on for
  the IOMMU, will be able to use more than 255 vCPUs.
  <span class="since">Since 3.4.0</span> (QEMU/KVM only)

-- 
Andrea Bolognani / Red Hat / Virtualization


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