Re: [libvirt] [Qemu-devel] [RFC 0/5] Allow object-add on X86CPU subclasses, for CPU model probing

On Fri, May 02, 2014 at 03:45:03PM +0200, Igor Mammedov wrote: > On Wed, 30 Apr 2014 17:29:28 -0300 > Eduardo Habkost <ehabkost(a)redhat.com&gt; wrote: > > > This series allows management code to use object-add on X86CPU subclasses, so it > Is there any reason why "device-add" couldn't be used? It needs to work with "-machine none", device_add requires a bus to exist, and there is no icc-bus on machine_none.

The first thing I considered was making icc-bus user-creatable. Then I noticed it wouldn't work because object-add always add objects to /objects, not inside the qdev hierarchy (that's where device_add looks for the bus). So, allowing device_add could be possible, but would require changing more basic infrastructure: either allowing bus-less devices on device_add, or allowing device_add to add devices outside the qdev hierarchy, or allowing object-add to create objects outside /objects. Simply making CPU objects work with object-add was much simpler and less intrusive. And it had the interesting side-effect of _not_ doing things that are not required for CPU model probing (like creating an actual VCPU thread). > > > > can use it to probe for CPU model information without re-running QEMU. The main > > use case for this is to allow management code to create CPU objects and query > > the "feature-words" and "filtered-features" properties on the new objects, to > > find out which features each CPU model needs, and to do the same using the > > "host" CPU model to check which features can be enabled in a given host. > > > > There's experimental libvirt code to use the new command at: > > https://github.com/ehabkost/libvirt/tree/work/cpu-feature-word-query > > The experimental code just create the CPU objects to query for feature > > information, but doesn't do anything with that data. > > > > Eduardo Habkost (5): > > cpu: Initialize cpu->stopped=true earlier > > cpu: Don't try to pause CPUs if they are already stopped > > pc: Don't crash on apic_accept_pic_intr() if CPU has no apic_state > > target-i386: Make CPU objects user-creatable > > target-i386: Report QOM class name for CPU definitions > > > > cpus.c | 13 ++++++++++--- > > exec.c | 1 + > > hw/i386/pc.c | 2 +- > > qapi-schema.json | 6 +++++- > > target-i386/cpu.c | 7 +++++++ > > 5 files changed, 24 insertions(+), 5 deletions(-) > > >