[libvirt] [PATCH 1/2] conf: Add support for preallocated fd memory

[Daniel P. Berrange]

On Tue, Oct 04, 2016 at 05:07:16PM +0200, Michal Privoznik wrote:
> On 29.09.2016 10:56, Jaroslav Safka wrote:
> > This first change introduces xml parsing support for preallocated
> > shared file descriptor based memory backing.
> > It allows vhost-user to be used without hugepages.
> > 
> > New xml elements:
> > <memoryBacking>
> >   <source type='file|anonymous' path='/path/to/qemu/' />

I'm pretty sure I said previously that path should *not* be
present in the XML, as that is a linux-ism / internal impl
detail not appropriate to expose.

> >   <access Mode='shared|private'/>
> >   <allocation mode='immediate|ondemand'/>
> > </memoryBacking>
> 
> Okay, this is definitely interesting approach (not only because while
> reviewing this, I've found an old branch in my git where I've started to
> work on this).
> 
> Frankly, I don't know if this is a good API or not. Historically, we
> required Dan's ACK on XML schema :-)

It is mostly ok, but what I think is missing though is integration
with the existing logic in this area.

eg we have a access mode attribute on the NUMA cell:

      <cell id='1' cpus='4-7' memory='512000' unit='KiB' memAccess='shared'/>

if this attribute is *not* specified on the NUMA cell,
then the parser should be auto-filling it based on
the top level <access mode> element. And of course test
files to demonstrate that is working.



> > ---
> >  docs/schemas/domaincommon.rng                      |  37 +++++
> >  src/conf/domain_conf.c                             | 149 ++++++++++++++++-----
> >  src/conf/domain_conf.h                             |  34 +++++
> >  .../qemuxml2argv-memorybacking-set.xml             |  32 +++++
> >  .../qemuxml2argv-memorybacking-unset.xml           |  32 +++++
> >  .../qemuxml2xmlout-memorybacking-set.xml           |  40 ++++++
> >  .../qemuxml2xmlout-memorybacking-unset.xml         |  40 ++++++
> >  tests/qemuxml2xmltest.c                            |   3 +
> >  8 files changed, 334 insertions(+), 33 deletions(-)
> >  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-memorybacking-set.xml
> >  create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-memorybacking-unset.xml
> >  create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-memorybacking-set.xml
> >  create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-memorybacking-unset.xml
> 
> You need to update the docs too. formatdomain.html.in to be more precise.


Regards,
Daniel
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