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Re: [libvirt] [PATCH V3 1/2] Intorduce file descriptor set for QEMU domains



On 02/07/2013 10:12 AM, Daniel P. Berrange wrote:
On Mon, Feb 04, 2013 at 07:12:37PM -0500, Stefan Berger wrote:
Create field in virDomainDeviceInfo structure to hold
file descriptor set the device is associated with. Have
the number written into the Device Info XML and parsed
from the XML.

Remember the next-toy use file descriptor set in the QEMU
private domain structure.
Upon libvirt restart determine the maximum file descriptor
set used in the Device Info XML and remember the
next-to-use file descriptor set in the QEMU private domain
structure.

Upon termination of a domain, reset the next-to-use file
descriptor set to its initial value '1'.

Stefan Berger <stefanb linux vnet ibm com>

---
  src/conf/capabilities.h |    5 ++++-
  src/conf/domain_conf.c  |   20 +++++++++++++++++---
  src/conf/domain_conf.h  |    1 +
  src/lxc/lxc_domain.c    |    3 ++-
  src/qemu/qemu_domain.c  |   23 ++++++++++++++++++++++-
  src/qemu/qemu_domain.h  |    2 ++
  src/qemu/qemu_process.c |    2 ++
  7 files changed, 50 insertions(+), 6 deletions(-)
I really don't like the fact that we're modifying the virDomainDef
structs, which are intended to hold static config description, to
also hold QEMU specific dynamic state. We did this in the past
before we had the per-driver 'privateData' associated with
virDomainObjPtr instances.

In these patches we are storing the fdset that's in use by a particular device in the virDomainDeviceInfo structure and are persisting that fdset number next to the device's alias into XML written into /var/run/libvirt/qemu to be able to restore it upon libvirt restart. Now we would either need a similar per-device structure in parallel to those virDomainDeviceInfo structures or connect a QEMU private data structure to that virDomainDeviceInfo structure for storing the dynamic data and to keep reference back to the device. Not sure what's the best path ...

This is how the per-device XML in /var/run/libvirt/qemu/xyz.xml looks now:

      <serial type='pipe'>
        <source path='/tmp/testpipe'/>
        <target port='1'/>
        <alias name='serial1' fdset='3'/>
      </serial>

Regards,
   Stefan


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