| Message ID | 159362467562.36204.11074523095942812006.stgit@naples-babu.amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fix couple of issues with AMD topology | expand |
On Wed, 01 Jul 2020 12:31:15 -0500 Babu Moger <babu.moger@amd.com> wrote: > Noticed the following command failure while testing CPU hotplug. > > $ 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 > > 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 is happening after the addition of new field node_id in X86CPUTopoIDs > structure. The node_id field is uninitialized while calling > apicid_from_topo_ids. The problem is discussed in the thread below. > https://lore.kernel.org/qemu-devel/20200602171838.GG577771@habkost.net/ > > Fix the problem by initializing the node_id from the device being added. > > Fixes: > Link: https://bugzilla.redhat.com/show_bug.cgi?id=1828750 > > Signed-off-by: Babu Moger <babu.moger@amd.com> > --- > hw/i386/pc.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index e613b2299f..aa9fb48834 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -1553,6 +1553,15 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev, > cpu->die_id = 0; > } > so this is from 'if (cpu->apic_id == UNASSIGNED_APIC_ID) {' branch, meaning cpu comes from -device/device_add > + /* > + * If node_id is not set, initialize it to zero for now. If the user > + * does not pass the correct node in case of numa configuration, it > + * will be rejected eventually. > + */ > + if (cpu->node_id < 0) { which means that user hasn't provided 'node-id', in which case we should error out asking for specifying NUMA node-id along with other options (1) However that's not enough since by contract query-hotpluggbale-cpus shall provide all attributes necessary to hotplug CPU, which makes node-id is not an optional in case of EPYC cpu. So we need to initialize ms->possible_cpus->cpus[i].props.[has_]node_id by the time we start creating CPUs. here are 2 variants: (2) * single node: nodes_per_pkg 1 and ms->smp.sockets == 1 since it's the only node and mapping of RAM/CPU is unambigiuos, we can deal with it by moving auto_enable_numa into MachineState and enabling it in case EPYC CPU is used * multiple nodes: - ms->smp.sockets > 1 - nodes_per_pkg > 1 we can't make up NUMA nodes automatically, and have to ask user to use -numa options to provide nodes along with CPU/RAM mapping. So in case NUMA wasn't configured explicitly, we can only error out. (that also applies to CPU created implicitly by board '-smp X') (3) Once user supplied mapping we need to checks that it matches EPYC topology, (4) As for CPUID, current code in CPUID_Fn8000001E_ECX if (nodes <= 4) { /* here nodes is nodes_per_pkg */ / goes by stricly spec / *ecx = ((nodes - 1) << 8) | (topo_ids.pkg_id << 2) | topo_ids.node_id; /* makes up system wide NUMA node IDs which happen to match system wide NUMA node IDs created by -numa, when -smp + -numa produces nodes_per_pkg is in that range, basically user has no idea when this happens */ } else { /* makeup new algorithm system wide NUMA node IDs generation for out of spec behaviour */ } problem with both branches is that might lead to inconsistentcy between system wide NUMA node id in CPUID_Fn8000001E_ECX and the one configured with -numa which goes to SRAT ACPI table and should go to CPU::node-id property. Considering that out of spec behaviour is allowed we probably schould replace both branches with *ecx = ((nodes - 1) << 8) | cpu->node_id; which ensures consistency of system wide NUMA node ids and add checks for max nodes/max node id. checks could be done early in cpu's realize() function. > + cpu->node_id = 0; > + } > if (cpu->socket_id < 0) { > error_setg(errp, "CPU socket-id is not set"); > return; > @@ -1587,6 +1596,7 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev, > } > > topo_ids.pkg_id = cpu->socket_id; > + topo_ids.node_id = cpu->node_id; > topo_ids.die_id = cpu->die_id; > topo_ids.core_id = cpu->core_id; > topo_ids.smt_id = cpu->thread_id; >
diff --git a/hw/i386/pc.c b/hw/i386/pc.c index e613b2299f..aa9fb48834 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -1553,6 +1553,15 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev, cpu->die_id = 0; } + /* + * If node_id is not set, initialize it to zero for now. If the user + * does not pass the correct node in case of numa configuration, it + * will be rejected eventually. + */ + if (cpu->node_id < 0) { + cpu->node_id = 0; + } + if (cpu->socket_id < 0) { error_setg(errp, "CPU socket-id is not set"); return; @@ -1587,6 +1596,7 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev, } topo_ids.pkg_id = cpu->socket_id; + topo_ids.node_id = cpu->node_id; topo_ids.die_id = cpu->die_id; topo_ids.core_id = cpu->core_id; topo_ids.smt_id = cpu->thread_id;
Noticed the following command failure while testing CPU hotplug. $ 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 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 is happening after the addition of new field node_id in X86CPUTopoIDs structure. The node_id field is uninitialized while calling apicid_from_topo_ids. The problem is discussed in the thread below. https://lore.kernel.org/qemu-devel/20200602171838.GG577771@habkost.net/ Fix the problem by initializing the node_id from the device being added. Fixes: Link: https://bugzilla.redhat.com/show_bug.cgi?id=1828750 Signed-off-by: Babu Moger <babu.moger@amd.com> --- hw/i386/pc.c | 10 ++++++++++ 1 file changed, 10 insertions(+)