Re: [Qemu-devel] [PATCH v2] docs: add cpu-hotplug.txt

[Andrew Jones]

On Mon, Aug 15, 2016 at 11:48:59AM +0800, Dou Liyang wrote:
> Hi drew,
> 
> 在 2016年08月12日 23:44, Andrew Jones 写道:
> > 
> > Hi Dou,
> > 
> > I'm catching up on mail after vacation so I reviewed the wrong
> > version of this patch first... Darn. I'll try again with this
> > version. Please still check my comments in that old version though,
> > as I'm going faster through this one and may miss things that are
> > here too (although not all comments are still applicable)
> 
> Yes, I will.
> 
> 
> > > +For example, the following command-line:
> > > +
> > > + qemu [...] -smp 3,maxcpus=10,sockets=2,cores=2,threads=2
> > 
> > Same as my v0 comments. sockets*cores*threads must be exactly maxcpus
> 
> I see. I will modify the example.
> 
> However, when I executed the example in current QEMU, I can hotplug an
> CPU device in the location(socket-id=2,core-id=0,thread-id=1) which was
> not in the CPU topology successfully.
> 
> 1: If we need a judgment: "maxcpus==sockets*cores*threads" when parsing the
> command line.

Yes, I have a patch [1] for this. We can't make things overly strict now
though, as that would risk breaking old command lines. (Eventually we
can fix it by changing to a new interface - see whole thread of that
patch [2])

> 
> 2: If replacing the maxcpus by the sockets*cores*threads in QEMU when a
> complete topology is given.

Yes, somewhere in that thread we had a lengthy discussion about it.
In the end, I think agreed to maxcpus being an optional parameter.
However, if it is given, then checking it's correct, and erroring out
when it isn't, is really the only sane course of action.

[1] https://www.mail-archive.com/address@hidden/msg376965.html
[2] https://www.mail-archive.com/address@hidden/msg376961.html

Thanks,
drew