Re: [PATCH v4 1/6] hw/loongarch/virt: Add CPU topology support

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 18 Nov 2024 17:10:29 +0100
Igor Mammedov <imammedo@redhat.com> wrote:

> On Tue, 12 Nov 2024 10:17:33 +0800
> Bibo Mao <maobibo@loongson.cn> wrote:
> 
> > Add topological relationships for Loongarch VCPU and initialize
> > topology member variables. Also physical cpu id calculation
> > method comes from its topo information.

hmm,

maybe split patch on 3 parts,

* initialize topo in possible CPUs
* add topo properties to CPU
* modify main cpu creation loop
  (I'd reorder that after 2/6, so you'd have pre_plug handler in
    place to move code to)

> > 
> > Co-developed-by: Xianglai Li <lixianglai@loongson.cn>
> > Signed-off-by: Bibo Mao <maobibo@loongson.cn>
> > ---
> >  docs/system/loongarch/virt.rst | 31 +++++++++++++++
> >  hw/loongarch/virt.c            | 73 ++++++++++++++++++++++++++++------
> >  target/loongarch/cpu.c         | 12 ++++++
> >  target/loongarch/cpu.h         | 16 ++++++++
> >  4 files changed, 119 insertions(+), 13 deletions(-)
> > 
> > diff --git a/docs/system/loongarch/virt.rst b/docs/system/loongarch/virt.rst
> > index 172fba079e..8daf60785f 100644
> > --- a/docs/system/loongarch/virt.rst
> > +++ b/docs/system/loongarch/virt.rst
> > @@ -28,6 +28,37 @@ The ``qemu-system-loongarch64`` provides emulation for virt
> >  machine. You can specify the machine type ``virt`` and
> >  cpu type ``la464``.
> >  
> > +CPU Topology
> > +------------
> > +
> > +The ``LA464`` type CPUs have the concept of Socket Core and Thread.
> > +
> > +For example:
> > +
> > +``-smp 1,maxcpus=M,sockets=S,cores=C,threads=T``
> > +
> > +The above parameters indicate that the machine has a maximum of ``M`` vCPUs and
> > +``S`` sockets, each socket has ``C`` cores, each core has ``T`` threads,
> > +and each thread corresponds to a vCPU.
> > +
> > +Then ``M`` ``S`` ``C`` ``T`` has the following relationship:
> > +
> > +``M = S * C * T``
> > +
> > +In the CPU topology relationship, When we know the ``socket_id`` ``core_id``
> > +and ``thread_id`` of the CPU, we can calculate its ``arch_id``:
> > +
> > +``arch_id = (socket_id * S) + (core_id * C) + (thread_id * T)``  
> 
> Is there a spec or some other reference where all of this is described?
> (or is that a made up just for QEMU?)
> 
> 
> > +
> > +Similarly, when we know the ``arch_id`` of the CPU,
> > +we can also get its ``socket_id`` ``core_id`` and ``thread_id``:
> > +
> > +``socket_id = arch_id / (C * T)``
> > +
> > +``core_id = (arch_id / T) % C``
> > +
> > +``thread_id = arch_id % T``
> > +
> >  Boot options
> >  ------------
> >  
> > diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
> > index 9a635d1d3d..1ed5130edf 100644
> > --- a/hw/loongarch/virt.c
> > +++ b/hw/loongarch/virt.c
> > @@ -1143,9 +1143,9 @@ static void virt_init(MachineState *machine)
> >      LoongArchVirtMachineState *lvms = LOONGARCH_VIRT_MACHINE(machine);
> >      int i;
> >      hwaddr base, size, ram_size = machine->ram_size;
> > -    const CPUArchIdList *possible_cpus;
> >      MachineClass *mc = MACHINE_GET_CLASS(machine);
> >      CPUState *cpu;
> > +    Object *cpuobj;
> >  
> >      if (!cpu_model) {
> >          cpu_model = LOONGARCH_CPU_TYPE_NAME("la464");
> > @@ -1163,13 +1163,30 @@ static void virt_init(MachineState *machine)
> >      memory_region_add_subregion(&lvms->system_iocsr, 0, &lvms->iocsr_mem);
> >  
> >      /* Init CPUs */
> > -    possible_cpus = mc->possible_cpu_arch_ids(machine);  
> I'd keep this, and use below, it makes line shorter
> 
> 
> > -    for (i = 0; i < possible_cpus->len; i++) {
> > -        cpu = cpu_create(machine->cpu_type);
> > +    mc->possible_cpu_arch_ids(machine);
> > +    for (i = 0; i < machine->smp.cpus; i++) {
> > +        cpuobj = object_new(machine->cpu_type);
> > +        if (cpuobj == NULL) {
> > +            error_report("Fail to create object with type %s ",
> > +                         machine->cpu_type);
> > +            exit(EXIT_FAILURE);
> > +        }
> > +
> > +        cpu = CPU(cpuobj);  
> 
> >          cpu->cpu_index = i;  
> this probably should be in _pre_plug handler,
> also see
> (a15d2728a9aa pc: Init CPUState->cpu_index with index in possible_cpus[])
> for why x86 does it. 
> 
> >          machine->possible_cpus->cpus[i].cpu = cpu;
> > -        lacpu = LOONGARCH_CPU(cpu);
> > +        lacpu = LOONGARCH_CPU(cpuobj);  
> 
> >          lacpu->phy_id = machine->possible_cpus->cpus[i].arch_id;  
> Given above is derived from topo data set below, I'd move above above
> to pre_plug time, and calculate/set it there based on topo data.
> There is no point in setting both at the same place. 
> 
> > +        object_property_set_int(cpuobj, "socket-id",
> > +                                machine->possible_cpus->cpus[i].props.socket_id,
> > +                                NULL);
> > +        object_property_set_int(cpuobj, "core-id",
> > +                                machine->possible_cpus->cpus[i].props.core_id,
> > +                                NULL);
> > +        object_property_set_int(cpuobj, "thread-id",
> > +                                machine->possible_cpus->cpus[i].props.thread_id,
> > +                                NULL);
> > +        qdev_realize_and_unref(DEVICE(cpuobj), NULL, &error_fatal);
> >      }
> >      fdt_add_cpu_nodes(lvms);
> >      fdt_add_memory_nodes(machine);
> > @@ -1286,6 +1303,35 @@ static void virt_initfn(Object *obj)
> >      virt_flash_create(lvms);
> >  }
> >  
> > +static int virt_get_arch_id_from_topo(MachineState *ms, LoongArchCPUTopo *topo)
> > +{
> > +    int arch_id, sock_vcpu_num, core_vcpu_num;
> > +
> > +    /*
> > +     * calculate total logical cpus across socket/core/thread.
> > +     * For more information on how to calculate the arch_id,
> > +     * you can refer to the CPU Topology chapter of the
> > +     * docs/system/loongarch/virt.rst document.
> > +     */
> > +    sock_vcpu_num = topo->socket_id * (ms->smp.threads * ms->smp.cores);
> > +    core_vcpu_num = topo->core_id * ms->smp.threads;
> > +
> > +    /* get vcpu-id(logical cpu index) for this vcpu from this topology */
> > +    arch_id = (sock_vcpu_num + core_vcpu_num) + topo->thread_id;
> > +
> > +    assert(arch_id >= 0 && arch_id < ms->possible_cpus->len);
> > +
> > +    return arch_id;
> > +}
> > +
> > +static void virt_get_topo_from_index(MachineState *ms,
> > +                                     LoongArchCPUTopo *topo, int index)
> > +{
> > +    topo->socket_id = index / (ms->smp.cores * ms->smp.threads);
> > +    topo->core_id = index / ms->smp.threads % ms->smp.cores;
> > +    topo->thread_id = index % ms->smp.threads;
> > +}
> > +
> >  static bool memhp_type_supported(DeviceState *dev)
> >  {
> >      /* we only support pc dimm now */
> > @@ -1385,8 +1431,9 @@ static HotplugHandler *virt_get_hotplug_handler(MachineState *machine,
> >  
> >  static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)
> >  {
> > -    int n;
> > +    int n, arch_id;
> >      unsigned int max_cpus = ms->smp.max_cpus;
> > +    LoongArchCPUTopo topo;
> >  
> >      if (ms->possible_cpus) {
> >          assert(ms->possible_cpus->len == max_cpus);
> > @@ -1397,17 +1444,17 @@ static const CPUArchIdList *virt_possible_cpu_arch_ids(MachineState *ms)
> >                                    sizeof(CPUArchId) * max_cpus);
> >      ms->possible_cpus->len = max_cpus;
> >      for (n = 0; n < ms->possible_cpus->len; n++) {
> > +        virt_get_topo_from_index(ms, &topo, n);
> > +        arch_id = virt_get_arch_id_from_topo(ms, &topo);
> > +        ms->possible_cpus->cpus[n].vcpus_count = 1;
> >          ms->possible_cpus->cpus[n].type = ms->cpu_type;
> > -        ms->possible_cpus->cpus[n].arch_id = n;
> > -
> > +        ms->possible_cpus->cpus[n].arch_id = arch_id;
> >          ms->possible_cpus->cpus[n].props.has_socket_id = true;
> > -        ms->possible_cpus->cpus[n].props.socket_id  =
> > -                                   n / (ms->smp.cores * ms->smp.threads);
> > +        ms->possible_cpus->cpus[n].props.socket_id = topo.socket_id;
> >          ms->possible_cpus->cpus[n].props.has_core_id = true;
> > -        ms->possible_cpus->cpus[n].props.core_id =
> > -                                   n / ms->smp.threads % ms->smp.cores;
> > +        ms->possible_cpus->cpus[n].props.core_id = topo.core_id;
> >          ms->possible_cpus->cpus[n].props.has_thread_id = true;
> > -        ms->possible_cpus->cpus[n].props.thread_id = n % ms->smp.threads;
> > +        ms->possible_cpus->cpus[n].props.thread_id = topo.thread_id;
> >      }
> >      return ms->possible_cpus;
> >  }
> > diff --git a/target/loongarch/cpu.c b/target/loongarch/cpu.c
> > index 57cc4f314b..a99e22094e 100644
> > --- a/target/loongarch/cpu.c
> > +++ b/target/loongarch/cpu.c
> > @@ -16,6 +16,7 @@
> >  #include "kvm/kvm_loongarch.h"
> >  #include "exec/exec-all.h"
> >  #include "cpu.h"
> > +#include "hw/qdev-properties.h"
> >  #include "internals.h"
> >  #include "fpu/softfloat-helpers.h"
> >  #include "cpu-csr.h"
> > @@ -725,6 +726,7 @@ static void loongarch_cpu_init(Object *obj)
> >      timer_init_ns(&cpu->timer, QEMU_CLOCK_VIRTUAL,
> >                    &loongarch_constant_timer_cb, cpu);
> >  #endif
> > +    cpu->phy_id = UNSET_PHY_ID;
> >  #endif
> >  }
> >  
> > @@ -823,6 +825,14 @@ static int64_t loongarch_cpu_get_arch_id(CPUState *cs)
> >  }
> >  #endif
> >  
> > +static Property loongarch_cpu_properties[] = {
> > +    DEFINE_PROP_INT32("socket-id", LoongArchCPU, socket_id, 0),
> > +    DEFINE_PROP_INT32("core-id", LoongArchCPU, core_id, 0),
> > +    DEFINE_PROP_INT32("thread-id", LoongArchCPU, thread_id, 0),
> > +    DEFINE_PROP_INT32("node-id", LoongArchCPU, node_id, CPU_UNSET_NUMA_NODE_ID),
> > +    DEFINE_PROP_END_OF_LIST()
> > +};
> > +
> >  static void loongarch_cpu_class_init(ObjectClass *c, void *data)
> >  {
> >      LoongArchCPUClass *lacc = LOONGARCH_CPU_CLASS(c);
> > @@ -830,6 +840,7 @@ static void loongarch_cpu_class_init(ObjectClass *c, void *data)
> >      DeviceClass *dc = DEVICE_CLASS(c);
> >      ResettableClass *rc = RESETTABLE_CLASS(c);
> >  
> > +    device_class_set_props(dc, loongarch_cpu_properties);
> >      device_class_set_parent_realize(dc, loongarch_cpu_realizefn,
> >                                      &lacc->parent_realize);
> >      resettable_class_set_parent_phases(rc, NULL, loongarch_cpu_reset_hold, NULL,
> > @@ -854,6 +865,7 @@ static void loongarch_cpu_class_init(ObjectClass *c, void *data)
> >  #ifdef CONFIG_TCG
> >      cc->tcg_ops = &loongarch_tcg_ops;
> >  #endif
> > +    dc->user_creatable = true;
> >  }
> >  
> >  static const gchar *loongarch32_gdb_arch_name(CPUState *cs)
> > diff --git a/target/loongarch/cpu.h b/target/loongarch/cpu.h
> > index 86c86c6c95..7472df0521 100644
> > --- a/target/loongarch/cpu.h
> > +++ b/target/loongarch/cpu.h
> > @@ -19,6 +19,12 @@
> >  #include "cpu-csr.h"
> >  #include "cpu-qom.h"
> >  
> > +/*
> > + * CPU can't have 0xFFFFFFFF physical ID, use that value to distinguish
> > + * that physical ID hasn't been set yet  
> 
> pointer to CPU spec/doc here would be nice to have
> 
> > + */
> > +#define UNSET_PHY_ID 0xFFFFFFFF
> > +
> >  #define IOCSRF_TEMP             0
> >  #define IOCSRF_NODECNT          1
> >  #define IOCSRF_MSI              2
> > @@ -390,6 +396,12 @@ typedef struct CPUArchState {
> >  #endif
> >  } CPULoongArchState;
> >  
> > +typedef struct LoongArchCPUTopo {
> > +    int32_t socket_id;  /* socket-id of this VCPU */
> > +    int32_t core_id;    /* core-id of this VCPU */
> > +    int32_t thread_id;  /* thread-id of this VCPU */
> > +} LoongArchCPUTopo;
> > +
> >  /**
> >   * LoongArchCPU:
> >   * @env: #CPULoongArchState
> > @@ -404,6 +416,10 @@ struct ArchCPU {
> >      uint32_t  phy_id;
> >      OnOffAuto lbt;
> >      OnOffAuto pmu;
> > +    int32_t socket_id;  /* socket-id of this VCPU */
> > +    int32_t core_id;    /* core-id of this VCPU */
> > +    int32_t thread_id;  /* thread-id of this VCPU */
> > +    int32_t node_id;    /* NUMA node of this VCPU */
> >  
> >      /* 'compatible' string for this CPU for Linux device trees */
> >      const char *dtb_compatible;  
>