Re: [Qemu-devel] [PATCH 1/2] sched: add virt sched domain for the guest

[Dave Hansen]

On 05/23/2012 01:48 AM, Peter Zijlstra wrote:
> On Wed, 2012-05-23 at 16:34 +0800, Liu ping fan wrote:
>> > so we need to migrate some of vcpus from node-B to node-A, or to
>> > node-C.
> This is absolutely broken, you cannot do that.
> 
> A guest task might want to be node affine, it looks at the topology sets
> a cpu affinity mask and expects to stay on that node.
> 
> But then you come along, and flip one of those cpus to another node. The
> guest task will now run on another node and get remote memory accesses.

Insane, sure.  But, if the node has physically gone away, what do we do?
 I think we've got to either kill the guest, or let it run somewhere
suboptimal.  Sounds like you're advocating killing it. ;)