On Mon, 13 Jul 2020 11:43:33 -0500
Babu Moger <babu.mo...@amd.com> wrote:
> On 7/13/20 11:17 AM, Igor Mammedov wrote:
> > On Mon, 13 Jul 2020 10:02:22 -0500
> > Babu Moger <babu.mo...@amd.com> wrote:
> >
> >>> -----Original Message-----
> >>> From: Igor Mammedov <imamm...@redhat.com>
> >>> Sent: Monday, July 13, 2020 4:08 AM
> >>> To: Moger, Babu <babu.mo...@amd.com>
> >>> Cc: pbonz...@redhat.com; r...@twiddle.net; ehabk...@redhat.com; qemu-
> >>> de...@nongnu.org
> >>> Subject: Re: [PATCH v2 1/3] hw/i386: Initialize topo_ids from
> >>> CpuInstanceProperties
> > [...]
> >>>> +
> >>>> +/*
> >>>> + * Initialize topo_ids from CpuInstanceProperties
> >>>> + * node_id in CpuInstanceProperties(or in CPU device) is a sequential
> >>>> + * number, but while building the topology
> >>>
> >>>> we need to separate it for
> >>>> + * each socket(mod nodes_per_pkg).
> >>> could you clarify a bit more on why this is necessary?
> >>
> >> If you have two sockets and 4 numa nodes, node_id in CpuInstanceProperties
> >> will be number sequentially as 0, 1, 2, 3. But in EPYC topology, it will
> >> be 0, 1, 0, 1( Basically mod % number of nodes per socket).
> >
> > I'm confused, let's suppose we have 2 EPYC sockets with 2 nodes per socket
> > so APIC id woulbe be composed like:
> >
> > 1st socket
> > pkg_id(0) | node_id(0)
> > pkg_id(0) | node_id(1)
> >
> > 2nd socket
> > pkg_id(1) | node_id(0)
> > pkg_id(1) | node_id(1)
> >
> > if that's the case, then EPYC's node_id here doesn't look like
> > a NUMA node in the sense it's usually used
> > (above config would have 4 different memory controllers => 4 conventional
> > NUMA nodes).
>
> EPIC model uses combination of socket id and node id to identify the numa
> nodes. So, it internally uses all the information.
well with above values, EPYC's node_id doesn't look like it's specifying
a machine numa node, but rather a node index within single socket. In which
case, it doesn't make much sense calling it NUMA node_id, it's rather some
index within a socket. (it starts looking like terminology is all mixed up)
If you have access to a milti-socket EPYC machine, can you dump and post here
its apic ids, pls?
>
> >
> > I wonder if linux guest actually uses node_id encoded in apic id for
> > configuring/checking numa structures, or it just uses whatever ACPI SRAT
> > table provided.
> >
> >>>> + */
> >>>> +static inline void x86_init_topo_ids(X86CPUTopoInfo *topo_info,
> >>>> + CpuInstanceProperties props,
> >>>> + X86CPUTopoIDs *topo_ids) {
> >>>> + topo_ids->smt_id = props.has_thread_id ? props.thread_id : 0;
> >>>> + topo_ids->core_id = props.has_core_id ? props.core_id : 0;
> >>>> + topo_ids->die_id = props.has_die_id ? props.die_id : 0;
> >>>> + topo_ids->node_id = props.has_node_id ?
> >>>> + props.node_id % MAX(topo_info->nodes_per_pkg,
> >>>> 1) : 0;
> >>>> + topo_ids->pkg_id = props.has_socket_id ? props.socket_id : 0; }
> >>>> /*
> >>>> * Make APIC ID for the CPU 'cpu_index'
> >>>> *
> >>>>
> >>
> >
>
