On Tue, Jun 02, 2020 at 04:59:19PM -0500, Babu Moger wrote:
>
>
> > -----Original Message-----
> > From: Eduardo Habkost <ehabk...@redhat.com>
> > Sent: Tuesday, June 2, 2020 12:19 PM
> > To: Moger, Babu <babu.mo...@amd.com>
> > Cc: marcel.apfelb...@gmail.com; pbonz...@redhat.com; r...@twiddle.net;
> > m...@redhat.com; imamm...@redhat.com; qemu-devel@nongnu.org
> > Subject: Re: [PATCH v7 07/13] hw/386: Add EPYC mode topology decoding
> > functions
> >
> > Hi,
> >
> > It looks like this series breaks -device and CPU hotplug:
> >
> > On Wed, Mar 11, 2020 at 05:53:34PM -0500, Babu Moger wrote:
> > > These functions add support for building EPYC mode topology given the smp
> > > details like numa nodes, cores, threads and sockets.
> > >
> > > The new apic id decoding is mostly similar to current apic id decoding
> > > except that it adds a new field node_id when numa configured. Removes all
> > > the hardcoded values. Subsequent patches will use these functions to build
> > > the topology.
> > >
> > > Following functions are added.
> > > apicid_llc_width_epyc
> > > apicid_llc_offset_epyc
> > > apicid_pkg_offset_epyc
> > > apicid_from_topo_ids_epyc
> > > x86_topo_ids_from_idx_epyc
> > > x86_topo_ids_from_apicid_epyc
> > > x86_apicid_from_cpu_idx_epyc
> > >
> > > The topology details are available in Processor Programming Reference
> > > (PPR)
> > > for AMD Family 17h Model 01h, Revision B1 Processors. The revision guides
> > are
> > > available from the bugzilla Link below.
> > > Link:
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugzilla.
> > kernel.org%2Fshow_bug.cgi%3Fid%3D206537&data=02%7C01%7Cbabu.m
> > oger%40amd.com%7C3487f40d37df4d59097d08d807190248%7C3dd8961fe488
> > 4e608e11a82d994e183d%7C0%7C0%7C637267151289763739&sdata=wE0
> > ukXIVh0l5eNQWsv6VDE9UZEVJmisofaW192gcZAI%3D&reserved=0
> > >
> > > Signed-off-by: Babu Moger <babu.mo...@amd.com>
> > > Acked-by: Igor Mammedov <imamm...@redhat.com>
> > > Acked-by: Michael S. Tsirkin <m...@redhat.com>
> > > ---
> > [...]
> > > typedef struct X86CPUTopoIDs {
> > > unsigned pkg_id;
> > > + unsigned node_id;
> >
> > You have added a new field here.
> >
> > > unsigned die_id;
> > > unsigned core_id;
> > > unsigned smt_id;
> > [...]
> > > +static inline apic_id_t
> > > +x86_apicid_from_topo_ids_epyc(X86CPUTopoInfo *topo_info,
> > > + const X86CPUTopoIDs *topo_ids)
> > > +{
> > > + return (topo_ids->pkg_id << apicid_pkg_offset_epyc(topo_info)) |
> > > + (topo_ids->node_id << apicid_node_offset_epyc(topo_info)) |
> >
> > You are using the new field here.
> >
> > > + (topo_ids->die_id << apicid_die_offset(topo_info)) |
> > > + (topo_ids->core_id << apicid_core_offset(topo_info)) |
> > > + topo_ids->smt_id;
> > > +}
> >
> > But you are not initializing node_id in one caller of
> > apicid_from_topo_ids():
> >
> > static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
> > DeviceState *dev, Error **errp)
> > {
> > [...]
> > X86CPUTopoIDs topo_ids;
> > [...]
> > if (cpu->apic_id == UNASSIGNED_APIC_ID) {
> > [...]
> > topo_ids.pkg_id = cpu->socket_id;
> > topo_ids.die_id = cpu->die_id;
> > topo_ids.core_id = cpu->core_id;
> > topo_ids.smt_id = cpu->thread_id;
> > cpu->apic_id = x86ms->apicid_from_topo_ids(&topo_info, &topo_ids);
> > }
> > [...]
> > }
> >
> > Result: -device is broken when using -cpu EPYC:
> >
> > $ qemu-system-x86_64 -machine q35,accel=kvm -smp
> > 1,maxcpus=2,cores=1,threads=1,sockets=2 -cpu EPYC -device EPYC-x86_64-
> > cpu,core-id=0,socket-id=1,thread-id=0
[1]
> > qemu-system-x86_64: -device EPYC-x86_64-cpu,core-id=0,socket-id=1,thread-
> > id=0: Invalid CPU [socket: 21855, die: 0, core: 0, thread: 0] with APIC ID
> > 21855,
> > valid index range 0:1
> >
> > This happens because APIC ID is calculated using uninitialized
> > memory.
> This patch should initialize the node_id. But I am not sure how to
> reproduce the bug. Can you please send me the full command line to
> reproduce the problem. Also test different options.
The full command line is above[1].
>
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 2128f3d6fe..047b4b9391 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1539,6 +1539,9 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
> if (cpu->apic_id == UNASSIGNED_APIC_ID) {
> int max_socket = (ms->smp.max_cpus - 1) /
> smp_threads / smp_cores / x86ms->smp_dies;
So, here's the input you are using to calculate topo_ids.node_id:
> + unsigned nr_nodes = MAX(topo_info.nodes_per_pkg, 1);
When is topo_info.nodes_per_pkg allowed to be 0?
> + unsigned cores_per_node = DIV_ROUND_UP((x86ms->smp_dies * smp_cores *
> + smp_threads), nr_nodes);
x86ms->smp_dies should be available at topo_info.dies_per_pkg,
smp_cores should available at topo_info.cores_per_die,
smp_threads should be available at topo_info.threads_per_core,
nr_nodes should be available at topo_info.nodes_per_pkg.
>
> /*
> * die-id was optional in QEMU 4.0 and older, so keep it optional
> @@ -1585,6 +1588,7 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
> topo_ids.die_id = cpu->die_id;
> topo_ids.core_id = cpu->core_id;
> topo_ids.smt_id = cpu->thread_id;
> + topo_ids.node_id = (cpu->core_id / cores_per_node) % nr_nodes;
apicid_from_topo_ids() have access to topo_info and topo_ids, If
all the information you need to calculate node_id is already
available inside topo_info + topo_ids, we could be calculating it
inside apicid_from_topo_ids(). Why don't we do it?
Also, is topo_ids.core_id really allowed to be larger than
cores_per_node when calling apicid_from_topo_ids()?
> cpu->apic_id = x86ms->apicid_from_topo_ids(&topo_info, &topo_ids);
> }
>
--
Eduardo
