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Re: [Qemu-devel] [PATCH v7] docs: add cpu-hotplug.txt
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH v7] docs: add cpu-hotplug.txt |
Date: |
Tue, 6 Sep 2016 17:05:18 -0300 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Tue, Aug 23, 2016 at 01:17:01PM +0800, Dou Liyang wrote:
> Hi Alexandre,
>
> At 08/22/2016 04:56 PM, Alexandre DERUMIER wrote:
> > Hello,
> >
> > I'm looking to implement cpu hotplug,
> >
> > and I have a question about cpu flags
> >
> > currently I have something like
> >
> > -cpu qemu64,+lahf_lm,+sep,+kvm_pv_unhalt,+kvm_pv_eoi,enforce
> > -smp 4,sockets=2,cores=2,maxcpus=4
> >
> >
> > Does I need to define flags like:
> >
> > -smp 2,sockets=2,cores=2,maxcpus=4
> > -device
> > qemu64-x86_64-cpu,+lahf_lm,+sep,+kvm_pv_unhalt,+kvm_pv_eoi,enforce,id=cpu1,socket-id=1,core-id=1,thread-id=0
>
> I think we don't need to do that.
> In my option, just like this:
>
> -device qemu64-x86_64-cpu,id=cpu1,socket-id=1,..
>
> Because QEMU sets the "-cpu" options in MachineState:
>
> current_machine->cpu_model = cpu_model;
>
> when you add a CPU, QEMU can get the flag from the MachineState.
You don't need to repeat the flags, but that's not because of
MachineState::cpu_model, but because of the semantics of -smp:
The option:
-smp MODEL,+FOO,+BAR
is internally translated to:
-global MODEL.FOO=on
-global MODEL.BAR=on
in addition to setting the CPU model for creating initial CPUs to
MODEL.
>
> > ...
> >
> > ?
> >
> >
> > Another question,
> > is -smp mandatory ? (if I want coldplug all cpus)
>
> it's not mandatory. such as this:
>
> ./x86_64-softmmu/qemu-system-x86_64 -m 1G /image/fedora.img
> -enable-kvm -monitor stdio
>
> (qemu) info cpus
> * CPU #0: pc=0xffffffff81060586 (halted) thread_id=4032
>
> the default number of CPUs is 1.
>
> >
> > -smp sockets=2,cores=2,maxcpus=4
>
> > -device qemu64-x86_64-cpu,id=cpu1,socket-id=1,core-id=1,thread-id=0
> > -device qemu64-x86_64-cpu,id=cpu1,socket-id=1,core-id=2,thread-id=0
> > -device qemu64-x86_64-cpu,id=cpu3,socket-id=2,core-id=1,thread-id=0
> > -device qemu64-x86_64-cpu,id=cpu4,socket-id=2,core-id=2,thread-id=0
> >
> > or does I need minimum 1 non unplugable cpu
As mentioned above, the default number of CPUs is 1, so "-smp
sockets=2" is the same as "-smp 1,sockets=2".
I assume you mean something like "-smp 0", but that doesn't work
today. I would like to eventually allow all CPUs to be created
using -device, but that's not possible yet.
> >
> > -smp 1,sockets=2,cores=2,maxcpus=4
> > -device qemu64-x86_64-cpu,id=cpu1,socket-id=1,core-id=2,thread-id=0
> > -device qemu64-x86_64-cpu,id=cpu3,socket-id=2,core-id=1,thread-id=0
> > -device qemu64-x86_64-cpu,id=cpu4,socket-id=2,core-id=2,thread-id=0
> >
>
> I think that is better, and the socket-id/core-id/thread-id starts at
> index 0
>
> I am new to the community. Please don't mind, and take with a grain of
> salt.
>
> Thanks,
> Dou
>
>
--
Eduardo
- Re: [Qemu-devel] [PATCH v7] docs: add cpu-hotplug.txt,
Eduardo Habkost <=