[libvirt PATCH 1/6] conf: add support for <acpi index='NNN'/> for PCI devices

[Daniel P. Berrangé]

On Wed, Apr 07, 2021 at 09:23:50AM +0200, Peter Krempa wrote:
> On Wed, Apr 07, 2021 at 09:17:36 +0200, Peter Krempa wrote:
> > On Tue, Apr 06, 2021 at 16:31:32 +0100, Daniel Berrange wrote:
> > > PCI devices can be associated with a unique integer index that is
> > > exposed via ACPI. In Linux OS with systemd, this value is used for
> > > provide a NIC device naming scheme that is stable across changes
> > > in PCI slot configuration.
> > > 
> > > Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> > > ---
> > >  docs/formatdomain.rst         |  6 +++
> > >  docs/schemas/domaincommon.rng | 73 +++++++++++++++++++++++++++++++++++
> > >  src/conf/device_conf.h        |  3 ++
> > >  src/conf/domain_conf.c        | 12 ++++++
> > >  4 files changed, 94 insertions(+)
> > > 
> > > diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
> > > index 7ba32ea9c1..5db0aac77a 100644
> > > --- a/docs/formatdomain.rst
> > > +++ b/docs/formatdomain.rst
> > > @@ -4363,6 +4363,7 @@ Network interfaces
> > >         <mac address='52:54:00:5d:c7:9e'/>
> > >         <boot order='1'/>
> > >         <rom bar='off'/>
> > > +       <acpi index='4'/>
> > >       </interface>
> > >     </devices>
> > >     ...
> > > @@ -4389,6 +4390,11 @@ when it's in the reserved VMware range by adding a ``type="static"`` attribute
> > >  to the ``<mac/>`` element. Note that this attribute is useless if the provided
> > >  MAC address is outside of the reserved VMWare ranges.
> > >  
> > > +:since:`Since 7.3.0`, one can set the ACPI index against network interfaces.
> > > +With some operating systems (eg Linux with systemd), the ACPI index is used
> > > +to provide network interface device naming, that is stable across changes
> > > +in PCI addresses assigned to the device.
> > 
> > Any range limits or uniqueness requirements worth mentioning?
> 
> QEMU / ACPI spec seems to be enforcing unique indexes:
> 
> commit 4fd7da4c0336c8fd822cd808d62f7ff8c9936aef
> Author: Igor Mammedov <imammedo at redhat.com>
> Date:   Mon Mar 15 14:00:59 2021 -0400
> 
>     pci: acpi: ensure that acpi-index is unique
> 
>     it helps to avoid device naming conflicts when guest OS is
>     configured to use acpi-index for naming.
>     Spec ialso says so:
> 
>     PCI Firmware Specification Revision 3.2
>     4.6.7.  _DSM for Naming a PCI or PCI Express Device Under Operating Systems
>     "
>     Instance number must be unique under \_SB scope. This instance number does not have to
>     be sequential in a given system configuration.
>     "
> 
> 
> The code isn't checking whether they are declared as unique.

IMHO libvirt doesn't need to duplicate checking that is already done
by QEMU for this.


Regards,
Daniel
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