[libvirt] [PATCHv2 3/6] conf: add <driver intremap> to <iommu>

Ján Tomko jtomko at redhat.com
Wed Apr 26 07:54:23 UTC 2017


On Mon, Apr 24, 2017 at 05:42:07PM -0400, John Ferlan wrote:
>
>
>On 04/20/2017 08:19 AM, Ján Tomko wrote:
>> Add a new attribute to control interrupt remapping.
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=1427005
>> ---
>>  docs/formatdomain.html.in                          | 22 ++++++++++++-
>>  docs/schemas/domaincommon.rng                      |  9 +++++
>>  src/conf/domain_conf.c                             | 38 +++++++++++++++++++---
>>  src/conf/domain_conf.h                             |  1 +
>>  .../qemuxml2argv-intel-iommu-irqchip.xml           |  4 ++-
>>  5 files changed, 68 insertions(+), 6 deletions(-)
>>
>> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
>> index abf089a..f5a8e76 100644
>> --- a/docs/formatdomain.html.in
>> +++ b/docs/formatdomain.html.in
>> @@ -7335,7 +7335,9 @@ qemu-kvm -net nic,model=? /dev/null
>>  <pre>
>>  ...
>>  <devices>
>> -  <iommu model='intel'/>
>> +  <iommu model='intel'>
>> +    <driver intremap='on'/>
>> +  </iommu>
>>  </devices>
>>  ...
>>  </pre>
>> @@ -7346,6 +7348,24 @@ qemu-kvm -net nic,model=? /dev/null
>>            Currently only the <code>intel</code> model is supported.
>>          </p>
>>        </dd>
>> +      <dt><code>driver</code></dt>
>> +      <dd>
>> +        <p>
>> +          The <code>driver</code> subelement can be used to configure
>> +          additional options:
>> +        </p>
>> +        <dl>
>> +          <dt><code>intremap</code></dt>
>> +          <dd>
>> +            <p>
>> +              The <code>intremap</code> attribute with possible values
>> +              <code>on</code> and <code>off</code> can be used to
>> +              turn on interrupt remapping. <span class="since">Since 3.3.0</span>
>> +              (QEMU only)
>
>It seems there is a relationship between this parameter and irqchip
>mode? IOW: Is it a requirement that irqchip be "split" or "on"? It's
>difficult to ascertain from the bz, but if so, then I'd expect a domain
>conf post processing in this patch.
>

Per http://wiki.qemu.org/Features/VT-d:
Currently, interrupt remapping does not support full kernel irqchip,
only "split" and "off" are supported.

We should not put current QEMU implementation limits into XML post
processing.

>Reading the bz it seems though that this parameter is optional for
>"certain" devices; however, for "general emulated devices" it's what is
>used to enable VT-d protection, but that could also be read as if
>'intel-iommu' is enabled, then VT-d protection is on by default with
>'intremap' just having some other affect.

Interrupt remapping is part of the VT-d feature.

>
>Is there something we could describe here at a very high level to
>describe the usefulness/need for this parameter?
>

IMO that is out of scope of the element description.

Jan
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