| Message ID | 20180920114406.20818-1-kchamart@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Deprecate QMP `cpu-add` | expand |
Kashyap Chamarthy <kchamart@redhat.com> writes: > The intended functionality of QMP command `cpu-add` is replaced by > `device_add` (and `query-hotpluggable-cpus`). So let's deprecate > `cpu-add`. > > A complete example of vCPU hotplug with the recommended way, using > `device_add`: > > (1) Launch QEMU as follows (note that the "maxcpus" is mandatory to > allow vCPU hotplug): > > $ qemu-system-x86_64 -display none -no-user-config -m 2048 \ > -nodefaults -monitor stdio -machine pc,accel=kvm,usb=off \ > -smp 1,maxcpus=2 -cpu IvyBridge-IBRS \ > -blockdev node-name=node-Base,driver=qcow2,file.driver=file,file.filename=./base.qcow2 \ > -device virtio-blk,drive=node-Base,id=virtio0 -qmp unix:/tmp/qmp-sock,server,nowait > > (2) Run 'qmp-shell' (located in the source tree) to connect to the > just-launched QEMU: > > $> ./qmp/qmp-shell -p -v /tmp/qmp-sock > [...] > (QEMU) > > (3) Check which socket is free to allow hotplugging a CPU: > > (QEMU) query-hotpluggable-cpus > { > "execute":"query-hotpluggable-cpus", > "arguments":{ > > } > } > { > "return":[ > { > "type":"IvyBridge-IBRS-x86_64-cpu", > "vcpus-count":1, > "props":{ > "socket-id":1, > "core-id":0, > "thread-id":0 > } > }, > { > "qom-path":"/machine/unattached/device[0]", > "type":"IvyBridge-IBRS-x86_64-cpu", > "vcpus-count":1, > "props":{ > "socket-id":0, > "core-id":0, > "thread-id":0 > } > } > ] > } > (QEMU) When I try this, JSON gets formatted slightly differently: { "execute": "query-hotpluggable-cpus", "arguments": {} } { "return": [ { "type": "IvyBridge-IBRS-x86_64-cpu", "vcpus-count": 1, "props": { "socket-id": 1, "core-id": 0, "thread-id": 0 } }, { "qom-path": "/machine/unattached/device[0]", "type": "IvyBridge-IBRS-x86_64-cpu", "vcpus-count": 1, "props": { "socket-id": 0, "core-id": 0, "thread-id": 0 } } ] } How come? > > (4) We can see that socket 1 is free, so use `device_add` to hotplug > "IvyBridge-IBRS-x86_64-cpu": > > (QEMU) device_add id=cpu-2 driver=IvyBridge-IBRS-x86_64-cpu socket-id=1 core-id=0 thread-id=0 > { > "execute": "device_add", > "arguments": { > "socket-id": 1, > "driver": "IvyBridge-IBRS-x86_64-cpu", > "id": "cpu-2", > "core-id": 0, > "thread-id": 0 > } > } > { > "return": {} > } > (QEMU) > > (5) Optionally, run QMP `query-cpus-fast` for some details about the > vCPUs. Publishing this in a commit message is much better than not publishing it. Still, can we find a better home somewhere under docs/? > Suggested-by: Eduardo Habkost <ehabkost@redhat.com > Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com> > --- > Also shouldn't we update tests/cpu-plug-test.c to make it use > `device_add`. Can take a stab at it, if you'd like me to. Yes, please. > --- > qapi/misc.json | 6 +++++- > qemu-deprecated.texi | 5 +++++ > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/qapi/misc.json b/qapi/misc.json > index d450cfef21..83bc9ad0ee 100644 > --- a/qapi/misc.json > +++ b/qapi/misc.json > @@ -1104,7 +1104,11 @@ > ## > # @cpu-add: > # > -# Adds CPU with specified ID > +# Adds CPU with specified ID. > +# > +# Notes: This command is deprecated. The `device_add` command should be > +# used instead. See the `query-hotpluggable-cpus` command for > +# details. > # > # @id: ID of CPU to be created, valid values [0..max_cpus) > # Eduardo pointed out that query-hotpluggable-cpus's documentation is lacking. Add a suitable TODO there? > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi > index 1b9c007f12..9c6d70d43a 100644 > --- a/qemu-deprecated.texi > +++ b/qemu-deprecated.texi > @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command. > The ``arch'' output member of the ``query-cpus-fast'' command is > replaced by the ``target'' output member. > > +@subsection cpu-add (since 3.1) > + > +The intended functionality of ``cpu-add'' command, which is the ability > +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. > + For me, "now" suggests device_add can achieve this since 3.1. Scratch "now"? > @section System emulator devices > > @subsection ivshmem (since 2.6.0)
On Thu, Sep 20, 2018 at 02:27:02PM +0200, Markus Armbruster wrote: > Kashyap Chamarthy <kchamart@redhat.com> writes: [...] > When I try this, JSON gets formatted slightly differently: > > { > "execute": "query-hotpluggable-cpus", > "arguments": {} > } > { > "return": [ > { > "type": "IvyBridge-IBRS-x86_64-cpu", > "vcpus-count": 1, > "props": { > "socket-id": 1, > "core-id": 0, > "thread-id": 0 > } > }, > { > "qom-path": "/machine/unattached/device[0]", > "type": "IvyBridge-IBRS-x86_64-cpu", > "vcpus-count": 1, > "props": { > "socket-id": 0, > "core-id": 0, > "thread-id": 0 > } > } > ] > } > > How come? You caught me :-). I actually get the same as you well. But I fudged the output by running it through: https://jsonformatter.curiousconcept.com/ with "2 Space Tab", but it doesn't make any difference. So I'll actually retain the original raw output from 'qmp-shell'. > > (4) We can see that socket 1 is free, so use `device_add` to hotplug > > "IvyBridge-IBRS-x86_64-cpu": > > > > (QEMU) device_add id=cpu-2 driver=IvyBridge-IBRS-x86_64-cpu socket-id=1 core-id=0 thread-id=0 > > { > > "execute": "device_add", > > "arguments": { > > "socket-id": 1, > > "driver": "IvyBridge-IBRS-x86_64-cpu", > > "id": "cpu-2", > > "core-id": 0, > > "thread-id": 0 > > } > > } > > { > > "return": {} > > } > > (QEMU) > > > > (5) Optionally, run QMP `query-cpus-fast` for some details about the > > vCPUs. > > Publishing this in a commit message is much better than not publishing > it. Still, can we find a better home somewhere under docs/? Good point. I'll make an 'cpu-hotplug.rst' in docs/ and submit it as a patch in v2. Hope that's okay with you. [...] > > --- > > Also shouldn't we update tests/cpu-plug-test.c to make it use > > `device_add`. Can take a stab at it, if you'd like me to. > > Yes, please. Igor was saying on IRC that we can fix the test when we _actually_ do the deprecation. So I'll make a TODO (and won't forget) to make it as a separate patch after we deprecate this. [...] > > # @id: ID of CPU to be created, valid values [0..max_cpus) > > # > > Eduardo pointed out that query-hotpluggable-cpus's documentation is > lacking. Add a suitable TODO there? Yes, will do. > > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi > > index 1b9c007f12..9c6d70d43a 100644 > > --- a/qemu-deprecated.texi > > +++ b/qemu-deprecated.texi > > @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command. > > The ``arch'' output member of the ``query-cpus-fast'' command is > > replaced by the ``target'' output member. > > > > +@subsection cpu-add (since 3.1) > > + > > +The intended functionality of ``cpu-add'' command, which is the ability > > +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. > > + > > For me, "now" suggests device_add can achieve this since 3.1. Scratch > "now"? Yes, will do. Thanks for the quick review!
On Thu, Sep 20, 2018 at 02:27:02PM +0200, Markus Armbruster wrote: > Kashyap Chamarthy <kchamart@redhat.com> writes: [...] > > --- > > qapi/misc.json | 6 +++++- > > qemu-deprecated.texi | 5 +++++ > > 2 files changed, 10 insertions(+), 1 deletion(-) > > > > diff --git a/qapi/misc.json b/qapi/misc.json > > index d450cfef21..83bc9ad0ee 100644 > > --- a/qapi/misc.json > > +++ b/qapi/misc.json > > @@ -1104,7 +1104,11 @@ > > ## > > # @cpu-add: > > # > > -# Adds CPU with specified ID > > +# Adds CPU with specified ID. > > +# > > +# Notes: This command is deprecated. The `device_add` command should be > > +# used instead. See the `query-hotpluggable-cpus` command for > > +# details. > > # > > # @id: ID of CPU to be created, valid values [0..max_cpus) > > # > > Eduardo pointed out that query-hotpluggable-cpus's documentation is > lacking. Add a suitable TODO there? Yes, please. > > > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi > > index 1b9c007f12..9c6d70d43a 100644 > > --- a/qemu-deprecated.texi > > +++ b/qemu-deprecated.texi > > @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command. > > The ``arch'' output member of the ``query-cpus-fast'' command is > > replaced by the ``target'' output member. > > > > +@subsection cpu-add (since 3.1) > > + > > +The intended functionality of ``cpu-add'' command, which is the ability > > +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. > > + > > For me, "now" suggests device_add can achieve this since 3.1. Scratch > "now"? Agreed. I would also try to write a shorter and simpler sentence, and mention query-hotpluggable-cpus. e.g.: The ``device_add'' command should be used for hotplugging VCPUs instead of ``cpu-add''. See the documentation of the ``query-hotpluggable-cpus'' command for additional details. > > > @section System emulator devices > > > > @subsection ivshmem (since 2.6.0)
Eduardo Habkost <ehabkost@redhat.com> writes: > On Thu, Sep 20, 2018 at 02:27:02PM +0200, Markus Armbruster wrote: >> Kashyap Chamarthy <kchamart@redhat.com> writes: > [...] >> > --- >> > qapi/misc.json | 6 +++++- >> > qemu-deprecated.texi | 5 +++++ >> > 2 files changed, 10 insertions(+), 1 deletion(-) >> > >> > diff --git a/qapi/misc.json b/qapi/misc.json >> > index d450cfef21..83bc9ad0ee 100644 >> > --- a/qapi/misc.json >> > +++ b/qapi/misc.json >> > @@ -1104,7 +1104,11 @@ >> > ## >> > # @cpu-add: >> > # >> > -# Adds CPU with specified ID >> > +# Adds CPU with specified ID. >> > +# >> > +# Notes: This command is deprecated. The `device_add` command should be >> > +# used instead. See the `query-hotpluggable-cpus` command for >> > +# details. >> > # >> > # @id: ID of CPU to be created, valid values [0..max_cpus) >> > # >> >> Eduardo pointed out that query-hotpluggable-cpus's documentation is >> lacking. Add a suitable TODO there? > > Yes, please. > >> >> > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi >> > index 1b9c007f12..9c6d70d43a 100644 >> > --- a/qemu-deprecated.texi >> > +++ b/qemu-deprecated.texi >> > @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command. >> > The ``arch'' output member of the ``query-cpus-fast'' command is >> > replaced by the ``target'' output member. >> > >> > +@subsection cpu-add (since 3.1) >> > + >> > +The intended functionality of ``cpu-add'' command, which is the ability >> > +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. >> > + >> >> For me, "now" suggests device_add can achieve this since 3.1. Scratch >> "now"? > > Agreed. > > I would also try to write a shorter and simpler sentence, and > mention query-hotpluggable-cpus. e.g.: > > The ``device_add'' command should be used for hotplugging VCPUs > instead of ``cpu-add''. See the documentation of the > ``query-hotpluggable-cpus'' command for additional details. Perhaps even Use ``device_add'' for hotplugging VCPUs instead of ``cpu-add''. See documentation of ``query-hotpluggable-cpus'' for additional details. > > > >> >> > @section System emulator devices >> > >> > @subsection ivshmem (since 2.6.0)
On Fri, Sep 21, 2018 at 08:30:54AM +0200, Markus Armbruster wrote: > Eduardo Habkost <ehabkost@redhat.com> writes: > > > On Thu, Sep 20, 2018 at 02:27:02PM +0200, Markus Armbruster wrote: > >> Kashyap Chamarthy <kchamart@redhat.com> writes: > > [...] > >> > --- > >> > qapi/misc.json | 6 +++++- > >> > qemu-deprecated.texi | 5 +++++ > >> > 2 files changed, 10 insertions(+), 1 deletion(-) > >> > > >> > diff --git a/qapi/misc.json b/qapi/misc.json > >> > index d450cfef21..83bc9ad0ee 100644 > >> > --- a/qapi/misc.json > >> > +++ b/qapi/misc.json > >> > @@ -1104,7 +1104,11 @@ > >> > ## > >> > # @cpu-add: > >> > # > >> > -# Adds CPU with specified ID > >> > +# Adds CPU with specified ID. > >> > +# > >> > +# Notes: This command is deprecated. The `device_add` command should be > >> > +# used instead. See the `query-hotpluggable-cpus` command for > >> > +# details. > >> > # > >> > # @id: ID of CPU to be created, valid values [0..max_cpus) > >> > # > >> > >> Eduardo pointed out that query-hotpluggable-cpus's documentation is > >> lacking. Add a suitable TODO there? > > > > Yes, please. > > > >> > >> > diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi > >> > index 1b9c007f12..9c6d70d43a 100644 > >> > --- a/qemu-deprecated.texi > >> > +++ b/qemu-deprecated.texi > >> > @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command. > >> > The ``arch'' output member of the ``query-cpus-fast'' command is > >> > replaced by the ``target'' output member. > >> > > >> > +@subsection cpu-add (since 3.1) > >> > + > >> > +The intended functionality of ``cpu-add'' command, which is the ability > >> > +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. > >> > + > >> > >> For me, "now" suggests device_add can achieve this since 3.1. Scratch > >> "now"? > > > > Agreed. > > > > I would also try to write a shorter and simpler sentence, and > > mention query-hotpluggable-cpus. e.g.: > > > > The ``device_add'' command should be used for hotplugging VCPUs > > instead of ``cpu-add''. See the documentation of the > > ``query-hotpluggable-cpus'' command for additional details. > > Perhaps even > > Use ``device_add'' for hotplugging VCPUs instead of ``cpu-add''. > See documentation of ``query-hotpluggable-cpus'' for additional > details. Nice, that's even more straightforward and simple.
diff --git a/qapi/misc.json b/qapi/misc.json index d450cfef21..83bc9ad0ee 100644 --- a/qapi/misc.json +++ b/qapi/misc.json @@ -1104,7 +1104,11 @@ ## # @cpu-add: # -# Adds CPU with specified ID +# Adds CPU with specified ID. +# +# Notes: This command is deprecated. The `device_add` command should be +# used instead. See the `query-hotpluggable-cpus` command for +# details. # # @id: ID of CPU to be created, valid values [0..max_cpus) # diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi index 1b9c007f12..9c6d70d43a 100644 --- a/qemu-deprecated.texi +++ b/qemu-deprecated.texi @@ -155,6 +155,11 @@ The ``query-cpus'' command is replaced by the ``query-cpus-fast'' command. The ``arch'' output member of the ``query-cpus-fast'' command is replaced by the ``target'' output member. +@subsection cpu-add (since 3.1) + +The intended functionality of ``cpu-add'' command, which is the ability +to hot-plug vCPUs, can now be achieved by the ``device_add'' command. + @section System emulator devices @subsection ivshmem (since 2.6.0)
The intended functionality of QMP command `cpu-add` is replaced by `device_add` (and `query-hotpluggable-cpus`). So let's deprecate `cpu-add`. A complete example of vCPU hotplug with the recommended way, using `device_add`: (1) Launch QEMU as follows (note that the "maxcpus" is mandatory to allow vCPU hotplug): $ qemu-system-x86_64 -display none -no-user-config -m 2048 \ -nodefaults -monitor stdio -machine pc,accel=kvm,usb=off \ -smp 1,maxcpus=2 -cpu IvyBridge-IBRS \ -blockdev node-name=node-Base,driver=qcow2,file.driver=file,file.filename=./base.qcow2 \ -device virtio-blk,drive=node-Base,id=virtio0 -qmp unix:/tmp/qmp-sock,server,nowait (2) Run 'qmp-shell' (located in the source tree) to connect to the just-launched QEMU: $> ./qmp/qmp-shell -p -v /tmp/qmp-sock [...] (QEMU) (3) Check which socket is free to allow hotplugging a CPU: (QEMU) query-hotpluggable-cpus { "execute":"query-hotpluggable-cpus", "arguments":{ } } { "return":[ { "type":"IvyBridge-IBRS-x86_64-cpu", "vcpus-count":1, "props":{ "socket-id":1, "core-id":0, "thread-id":0 } }, { "qom-path":"/machine/unattached/device[0]", "type":"IvyBridge-IBRS-x86_64-cpu", "vcpus-count":1, "props":{ "socket-id":0, "core-id":0, "thread-id":0 } } ] } (QEMU) (4) We can see that socket 1 is free, so use `device_add` to hotplug "IvyBridge-IBRS-x86_64-cpu": (QEMU) device_add id=cpu-2 driver=IvyBridge-IBRS-x86_64-cpu socket-id=1 core-id=0 thread-id=0 { "execute": "device_add", "arguments": { "socket-id": 1, "driver": "IvyBridge-IBRS-x86_64-cpu", "id": "cpu-2", "core-id": 0, "thread-id": 0 } } { "return": {} } (QEMU) (5) Optionally, run QMP `query-cpus-fast` for some details about the vCPUs. Suggested-by: Eduardo Habkost <ehabkost@redhat.com Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com> --- Also shouldn't we update tests/cpu-plug-test.c to make it use `device_add`. Can take a stab at it, if you'd like me to. --- qapi/misc.json | 6 +++++- qemu-deprecated.texi | 5 +++++ 2 files changed, 10 insertions(+), 1 deletion(-)