* Babu Moger (babu.mo...@amd.com) wrote: > > > > -----Original Message----- > > From: Eduardo Habkost <ehabk...@redhat.com> > > Sent: Wednesday, June 3, 2020 10:46 AM > > 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 > > > > On Wed, Jun 03, 2020 at 10:38:46AM -0500, Babu Moger wrote: > > > > > > > > > On 6/3/20 10:31 AM, Eduardo Habkost wrote: > > > > On Wed, Jun 03, 2020 at 10:22:10AM -0500, Babu Moger wrote: > > > >> > > > >> > > > >>> -----Original Message----- > > > >>> From: Eduardo Habkost <ehabk...@redhat.com> > > > >>> Sent: Tuesday, June 2, 2020 6:01 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 > > > >>> > > > >>> 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]. > > > >> > > > >> I just picked up the latest tree from > > > >> git clone > > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.qem > > u.org%2Fgit%2Fqemu.git&data=02%7C01%7Cbabu.moger%40amd.com%7 > > C4b409b77ff2c4c4ed90608d807d53570%7C3dd8961fe4884e608e11a82d994e1 > > 83d%7C0%7C0%7C637267959601716206&sdata=ih6bo9Wp0RbJgRpryzSa2 > > D0v6kr3Zfww%2B1uB%2FNyngk8%3D&reserved=0 qemu > > > >> Not seeing the problem. > > > >> > > > >> ./x86_64-softmmu/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 > > > >> VNC server running on ::1:5900 > > > >> > > > >> It appears to run ok. > > > > > > [2] > > > > > > >> > > > >>> > > > >>> > > > >>>> > > > >>>> 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? > > > >> > > > >> It will be zero if numa is not configured. Node_id will be zero for all > > > >> the cores. > > > >> > > > >>> > > > >>>> + 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()? > > > >> > > > >> Yes. It is. If we have two numa nodes and 8 cores. Then cores_per_node > > > >> is > > > >> 4. Nr_nodes =2. Yes. Core_id can be larger than cores_per_node. > > > > > > > > I assumed core_id identified the core inside a die, and the range > > > > would be [0, cores_per_die). This seems to be what > > > > apicid_from_topo_ids_epyc() expects. > > > > > > > > We need clearer documentation on the semantics of each *_id > > > > field, to avoid confusion. > > > > > > Ok. Sure. I will add that. Can you please clarify on how to repro the > > > issue. Marked the question at [2]. > > > > As it is usage of uninitialized memory, behavior is undefined and > > not guaranteed to crash. My QEMU binary was built with > > --enable-debug, maybe it makes it easier to reproduce. > > This patch works fine. Tested few combination. Will send the formal > version if patch looks good. > > diff --git a/include/hw/i386/topology.h b/include/hw/i386/topology.h > index 07239f95f4..cb28f0a57c 100644 > --- a/include/hw/i386/topology.h > +++ b/include/hw/i386/topology.h > @@ -140,6 +140,17 @@ static inline unsigned > apicid_pkg_offset_epyc(X86CPUTopoInfo *topo_info) > apicid_node_width_epyc(topo_info); > } > > +static inline unsigned x86_node_id_for_epyc(X86CPUTopoInfo *topo_info, > + const X86CPUTopoIDs *topo_ids) > +{ > + unsigned nr_nodes = MAX(topo_info->nodes_per_pkg, 1); > + unsigned cores_per_node = DIV_ROUND_UP((topo_info->dies_per_pkg * > + topo_info->cores_per_die * > + topo_info->threads_per_core), > + nr_nodes); > + > + return ((topo_ids->core_id / cores_per_node) % nr_nodes); > +} > /* > * Make APIC ID for the CPU based on Pkg_ID, Core_ID, SMT_ID > * > @@ -149,8 +160,11 @@ static inline apic_id_t > x86_apicid_from_topo_ids_epyc(X86CPUTopoInfo *topo_info, > const X86CPUTopoIDs *topo_ids) > { > + /* node_id can be uninitialized. Initialize here */ > + unsigned node_id = x86_node_id_for_epyc(topo_info, topo_ids); > + > return (topo_ids->pkg_id << apicid_pkg_offset_epyc(topo_info)) | > - (topo_ids->node_id << apicid_node_offset_epyc(topo_info)) | > + (node_id << apicid_node_offset_epyc(topo_info)) | > (topo_ids->die_id << apicid_die_offset(topo_info)) | > (topo_ids->core_id << apicid_core_offset(topo_info)) | > topo_ids->smt_id; >
What's the status of this? It seems to fix a hotplug case our QE hit (RH bz 1828750) Dave -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
