[libvirt PATCH v2 05/16] nodedev: add ability to list and parse defined mdevs

[Bjoern Walk]

Bjoern Walk <bwalk at linux.ibm.com> [2020-10-15, 09:41PM +0200]:
> Jonathon Jongsma <jjongsma at redhat.com> [2020-08-18, 09:47AM -0500]:
> > diff --git a/tests/nodedevmdevctldata/mdevctl-list-single.out.xml b/tests/nodedevmdevctldata/mdevctl-list-single.out.xml
> > new file mode 100644
> > index 0000000000..cb443346ef
> > --- /dev/null
> > +++ b/tests/nodedevmdevctldata/mdevctl-list-single.out.xml
> > @@ -0,0 +1,14 @@
> > +<device>
> > +  <name>mdev_783e6dbb_ea0e_411f_94e2_717eaad438bf</name>
> > +  <parent>matrix</parent>
> > +  <capability type='mdev'>
> > +    <type id='vfio_ap-passthrough'/>
> > +    <iommuGroup number='0'/>
> > +    <attr name='assign_adapter' value='5'/>
> > +    <attr name='assign_adapter' value='6'/>
> > +    <attr name='assign_domain' value='0xab'/>
> > +    <attr name='assign_control_domain' value='0xab'/>
> > +    <attr name='assign_domain' value='4'/>
> > +    <attr name='assign_control_domain' value='4'/>
> > +  </capability>
> > +</device>
> 
> I find this XML design for the an AP mdev rather unfortunate. First of
> all, it is really noisy and requires a lot of boiler-plate for the end
> user.
> 
> Secondly, which I think it more important, it introduces a completely
> new and different nomenclature compared to what we currently already
> have for AP-related devices, i.e. cards
> 
> 	virsh # nodedev-dumpxml ap_card05
> 	<device>
> 	  <name>ap_card05</name>
> 	  <path>/sys/devices/ap/card05</path>
> 	  <parent>computer</parent>
> 	  <driver>
> 		<name>cex4card</name>
> 	  </driver>
> 	  <capability type='ap_card'>
> 		<ap-adapter>0x05</ap-adapter>
> 	  </capability>
> 	</device>
> 
> and queues
> 
> 	virsh # nodedev-dumpxml ap_05_002a
> 	<device>
> 	  <name>ap_05_002a</name>
> 	  <path>/sys/devices/ap/card05/05.002a</path>
> 	  <parent>ap_card05</parent>
> 	  <driver>
> 		<name>cex4queue</name>
> 	  </driver>
> 	  <capability type='ap_queue'>
> 		<ap-adapter>0x05</ap-adapter>
> 		<ap-domain>0x002a</ap-domain>
> 	  </capability>
> 	</device>

I just figured that patches that implement that were not even sent
upstream... We will do so shortly. I would however welcome a discussion
on a sane and consistent XML design for both series.

> 
> This is really inconsistent and can be confusing for the end user.
> 
> Can we instead propose something along the lines
> 
> 	<device>
> 	  <name>mdev_783e6dbb_ea0e_411f_94e2_717eaad438bf</name>
> 	  <parent>matrix</parent>
> 	  <capability type='mdev'>
> 		<type id='vfio_ap-passthrough'/>
> 		<iommuGroup number='0'/>
> 		<ap-adapter>0x05</ap-adapter>
> 		<ap-adapter>0x06</ap-adapter>
> 		<ap-domain>0x002a</ap-domain>
> 		<ap-domain>0x0004</ap-domain>
> 		<ap-domain>0x00ab</ap-domain>
> 		<ap-control>0x04</ap-control>
> 	  </capability>
> 	</device>
> 
> plus any number of enclosing elements that we like for better readability?
> 
> Best,
> Bjoern
> 
> PS: I haven't read the whole patch series, we just have an internal
> discussion about AP support and the XML design came up. I know that we'd
> like to generically treat all mdevs as the same but we also should allow
> for vendor-specific attributes to be represented individually to what
> makes sense.
> 
> -- 
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> Linux on Z & Virtualization Development
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-- 
IBM Systems
Linux on Z & Virtualization Development
--------------------------------------------------
IBM Deutschland Research & Development GmbH
Schönaicher Str. 220, 71032 Böblingen
Phone: +49 7031 16 1819
--------------------------------------------------
Vorsitzende des Aufsichtsrats: Gregor Pillen
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294
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