Re: [Qemu-devel] [RFC PATCH v0] numa: API to lookup NUMA node by address

[Bharata B Rao <bharata@linux.vnet.ibm.com>]

On Mon, May 25, 2015 at 02:42:40PM -0300, Eduardo Habkost wrote:
> On Mon, May 25, 2015 at 01:17:57PM +0530, Bharata B Rao wrote:
> > On Thu, May 14, 2015 at 11:39:06AM +0200, Paolo Bonzini wrote:
> > > On 13/05/2015 20:06, Eduardo Habkost wrote:
> > > > Also, this introduces a circular dependency between pc-dimm.c and
> > > > numa.c. Instead of that, pc-dimm could simply notify us when a new
> > > > device is realized (with just (addr, end, node) as arguments), so we can
> > > > save the list of memory ranges inside struct node_info.
> > > > 
> > > > I wonder if the memory API already provides something that would help
> > > > us. Paolo, do you see a way we could simply use a MemoryRegion as input
> > > > to lookup the NUMA node?
> > > 
> > > No, but I guess you could add a numa_get/set_memory_region_node_id API
> > > that uses a hash table.  That's a variant of the "pc-dimm could simply
> > > notify" numa.c that you propose above.
> > 
> > While you say we can't use MemoryRegion as input to lookup the NUMA node,
> > you suggest that we add numa_get/set_memory_region_node_id. Does this API
> > get/set NUMA node id for the given MemoryRegion ? 
> 
> I was going to suggest that, but it would require changing the
> non-memdev code path to create a MemoryRegion for each node, too. So
> having a numa_set_mem_node_id(start_addr, end_addr, node_id) API would
> be simpler.

In order to save the list of memory ranges inside node_info, I tried this
approach where I call

numa_set_mem_node_id(dimm.addr, dimm.size, dimm.node) from

pc_dimm_realize(), but

the value of dimm.addr is finalized only later in ->plug().

So we would have to call this API from arch code like pc_dimm_plug().
Is that acceptable ?

Regards,
Bharata.