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> 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(-)
>
--
Eduardo