On Wed, Mar 18, 2015 at 11:49:59AM +1100, David Gibson wrote: > On Fri, Mar 13, 2015 at 05:26:36PM +0530, Bharata B Rao wrote: > > From: Bharata B Rao <bharata....@gmail.com> > > > > Currently CPUState.cpu_index is monotonically increasing and a newly > > created CPU always gets the next higher index. The next available > > index is calculated by counting the existing number of CPUs. This is > > fine as long as we only add CPUs, but there are architectures which > > are starting to support CPU removal too. For an architecture like PowerPC > > which derives its CPU identifier (device tree ID) from cpu_index, the > > existing logic of generating cpu_index values causes problems. > > > > With the currently proposed method of handling vCPU removal by parking > > the vCPU fd in QEMU > > (Ref: http://lists.gnu.org/archive/html/qemu-devel/2015-02/msg02604.html), > > generating cpu_index this way will not work for PowerPC. > > > > This patch changes the way cpu_index is handed out by maintaining > > a bit map of the CPUs that tracks both addition and removal of CPUs. > > > > I am not sure if this is the right and an acceptable approach. The > > alternative is to do something similar for PowerPC alone and not > > depend on cpu_index. > > > > I have tested this with out-of-the-tree patches for CPU hot plug and > > removal on x86 and sPAPR PowerPC. > > How does this interact with the tweaking of cpu indexes that spapr > does in order to configure the guest SMT mode on POWER7 and POWER8 > systems?
I am not changing the mapping of cpu_index to cpu_dt_id. So nothing should be change. Can you please point me to the piece of tweaking code that you are referring to above ? Regards, Bharata.
