On Fri, 2014-04-18 at 08:43 +1000, Alexey Kardashevskiy wrote: > On 04/18/2014 06:25 AM, Nishanth Aravamudan wrote: > > Hi Alexey, > > > > Prior to the $SUBJECT commit, we could present memoryless node0s to > > guests. Now, we indicate that we don't have the requisite 128M for the > > RMA if node 0 has no memory. Note that a memoryless node0 is possible > > under PowerVM (but not predictably present) so I was hoping to use KVM > > to test relevant fixes for memoryless nodes. > > > > I think this change is a misinterpretation of the PAPR standard, though. > > Yes, the RMA must be in the first block of memory, but that isn't > > necessarily on node 0. The topology of a PAPR-compliant guest does not > > require a node 0 (and in fact, under PowerVM, Linux doesn't actually > > require node 0 either, but it would under KVM). > > > > Thoughts? I suppose it's fine to say that node 0 must be sufficiently > > populated under KVM -- there's not really a reason to not have memory on > > a given node (except maybe ballooning). I can keep the commit reverted > > locally for testing purposes. Just wanted to see if the semantic change > > was intentional. > > > PAPR spec 2.7: > C.6.6 Memory Node > === > This section defines the PAPR modifications to the OF /memory node. In > PAPR, the memory allocated to an OS image > may be divided into a number of allocation units called “regions” or > “Logical Memory Blocks (LMB). An OS image > may be dynamically allocated additional regions or may be asked to release > regions. Each LMB is either represented in > the device tree by its own /memory node or by an entry in > /ibm,dynamic-reconfiguration-memory nodes > (see Section C.6.6.2‚ “ibm,dynamic-reconfiguration-memory‚” on page 1089). > The /memory node that refers to the > storage starting at real address zero (“reg” property starting at the value > zero) always remains allocated to an OS image. > > The client program is initially loaded into this storage, called the RMA, > that is represented by the first value of the > “reg” property of this first /memory node. > === > > The last sentence is why the change was made. It does not say "first > populated" node. I am adding Ben as he had very strong opinion about this > thing.
You are confusing device-tree node with NUMA nodes. Yes, it must be the LMB at address 0, which is the /memory node, but that doesn't have to be NUMA node 0. Cheers, Ben.
