[libvirt] [PATCH] xml: nodedev: make pci capability class element optional

[Nikolay Shirokovskiy]

On 21.03.2019 15:28, Erik Skultety wrote:
> On Thu, Mar 21, 2019 at 11:49:55AM +0000, Nikolay Shirokovskiy wrote:
>>
>>
>> On 21.03.2019 14:32, Erik Skultety wrote:
>>> On Thu, Mar 21, 2019 at 10:27:14AM +0300, Nikolay Shirokovskiy wrote:
>>>> Commit 3bd4ed46 introduced this element as required which
>>>> breaks backcompat for test driver. Let's make the element optional.
>>>>
>>>> Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy at virtuozzo.com>
>>>> ---
>>>>  docs/formatnode.html.in                            |  2 +-
>>>>  docs/schemas/nodedev.rng                           | 12 ++++++-----
>>>>  src/conf/node_device_conf.c                        | 23 +++++++++++-----------
>>>>  src/conf/node_device_conf.h                        |  2 +-
>>>>  src/node_device/node_device_udev.c                 |  2 +-
>>>>  .../pci_0000_02_10_7_sriov_pf_vfs_all.xml          |  1 -
>>>>  6 files changed, 22 insertions(+), 20 deletions(-)
>>>>
>>>> diff --git a/docs/formatnode.html.in b/docs/formatnode.html.in
>>>> index 5095b97..c2a8f8f 100644
>>>> --- a/docs/formatnode.html.in
>>>> +++ b/docs/formatnode.html.in
>>>> @@ -71,7 +71,7 @@
>>>>              include:
>>>>              <dl>
>>>>                <dt><code>class</code></dt>
>>>> -              <dd>Combined class, subclass and
>>>> +              <dd>Optional element for combined class, subclass and
>>>>                  programming interface codes as 6-digit hexadecimal number.
>>>>                  <span class="since">Since 5.2.0</span></dd>
>>>>                <dt><code>domain</code></dt>
>>>> diff --git a/docs/schemas/nodedev.rng b/docs/schemas/nodedev.rng
>>>> index 0f45d79..fe6ffa0 100644
>>>> --- a/docs/schemas/nodedev.rng
>>>> +++ b/docs/schemas/nodedev.rng
>>>> @@ -133,11 +133,13 @@
>>>>        <value>pci</value>
>>>>      </attribute>
>>>>
>>>> -    <element name='class'>
>>>> -      <data type="string">
>>>> -        <param name="pattern">0x[0-9a-fA-F]{6}</param>
>>>> -      </data>
>>>> -    </element>
>>>> +    <optional>
>>>> +      <element name='class'>
>>>> +        <data type="string">
>>>> +          <param name="pattern">0x[0-9a-fA-F]{6}</param>
>>>> +        </data>
>>>> +      </element>
>>>> +    </optional>
>>>>      <element name='domain'>
>>>>        <ref name='unsignedLong'/>
>>>>      </element>
>>>> diff --git a/src/conf/node_device_conf.c b/src/conf/node_device_conf.c
>>>> index 19c601a..b96d10c 100644
>>>> --- a/src/conf/node_device_conf.c
>>>> +++ b/src/conf/node_device_conf.c
>>>> @@ -208,7 +208,8 @@ virNodeDeviceCapPCIDefFormat(virBufferPtr buf,
>>>>  {
>>>>      size_t i;
>>>>
>>>> -    virBufferAsprintf(buf, "<class>0x%.6x</class>\n", data->pci_dev.klass);
>>>> +    if (data->pci_dev.klass >= 0)
>>>> +        virBufferAsprintf(buf, "<class>0x%.6x</class>\n", data->pci_dev.klass);
>>>
>>> Can 0 be a valid class? I mean semantically, can't 0 mean something like "no
>>> class"? I'm just wondering, whether we could report 0x000000, provided it
>>> doesn't denote a valid class already, instead of omitting the <class> element
>>> on the output, but then again, from mgmt app POV it doesn't make any difference
>>> to check whether the <class> element is missing or it reports 0 for devices
>>> that have no class specified.
>>>
>>> Do you have some further reading on the classes? I didn't manage to find
>>> anything that would help me decode the hex value.
>>
>> I found https://wiki.osdev.org/PCI. So looks like 0x000000 should be
>> treated as 'Unclassified/Non-VGA-Compatible devices'.
> 
> Hmm, do you know whether udev would report 0x000000 for devices which don't
> report any class code (if there are any such devices out there) or it woudln't
> report anything to us? In which case what your have in this patch is the only
> right thing to do.
> 

I need to take a look on udev/kernel code to answer the question...

Nikolay