Re: [Qemu-devel] [PATCH v9 05/11] numa: Extend CLI to provide initiator information for numa nodes

[Tao Xu]

On 8/15/2019 5:29 AM, Dan Williams wrote:
> On Tue, Aug 13, 2019 at 10:14 PM Tao Xu <address@hidden> wrote:
> > On 8/14/2019 10:39 AM, Dan Williams wrote:
> > > On Tue, Aug 13, 2019 at 8:00 AM Igor Mammedov <address@hidden> wrote:
> > > > On Fri,  9 Aug 2019 14:57:25 +0800
> > > > Tao <address@hidden> wrote:
> > > >
> > > > > From: Tao Xu <address@hidden>
[...]
> > > > > +    for (i = 0; i < machine->numa_state->num_nodes; i++) {
> > > > > +        if (numa_info[i].initiator_valid &&
> > > > > +            !numa_info[numa_info[i].initiator].has_cpu) {
> > > >                             ^^^^^^^^^^^^^^^^^^^^^^ possible out of bounds read, 
> > > > see bellow
> > > >
> > > > > +            error_report("The initiator-id %"PRIu16 " of NUMA node %d"
> > > > > +                         " does not exist.", numa_info[i].initiator, i);
> > > > > +            error_printf("\n");
> > > > > +
> > > > > +            exit(1);
> > > > > +        }
> > > > it takes care only about nodes that have cpus or memory-only ones that have
> > > > initiator explicitly provided on CLI. And leaves possibility to have
> > > > memory-only nodes without initiator mixed with nodes that have initiator.
> > > > Is it valid to have mixed configuration?
> > > > Should we forbid it?
> > >
> > > The spec talks about the "Proximity Domain for the Attached Initiator"
> > > field only being valid if the memory controller for the memory can be
> > > identified by an initiator id in the SRAT. So I expect the only way to
> > > define a memory proximity domain without this local initiator is to
> > > allow specifying a node-id that does not have an entry in the SRAT.
> > Hi Dan,
> >
> > So there may be a situation for the Attached Initiator field is not
> > valid? If true, I would allow user to input Initiator invalid.
>
> Yes it's something the OS needs to consider because the platform may
> not be able to meet the constraint that a single initiator is
> associated with the memory controller for a given memory target. In
> retrospect it would have been nice if the spec reserved 0xffffffff for
> this purpose, but it seems "not in SRAT" is the only way to identify
> memory that is not attached to any single initiator.
But As far as I konw, QEMU can't emulate a NUMA node "not in SRAT". I am 
wondering if it is effective only set Initiator invalid?