Re: [RFC PATCH v2 2/6] hw/arm/virt: DT: Add cpu-map

[wangyanan (Y)]

On 2021/5/13 14:58, Andrew Jones wrote:
> On Tue, Apr 13, 2021 at 04:07:41PM +0800, Yanan Wang wrote:
> > From: Andrew Jones <drjones@redhat.com>
> >
> > Support device tree CPU topology descriptions.
> >
> > Signed-off-by: Andrew Jones <drjones@redhat.com>
> > Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> > ---
> >   hw/arm/virt.c         | 41 ++++++++++++++++++++++++++++++++++++++++-
> >   include/hw/arm/virt.h |  1 +
> >   2 files changed, 41 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index 9f01d9041b..f4ae60ded9 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -352,10 +352,11 @@ static void fdt_add_cpu_nodes(const VirtMachineState *vms)
> >       int cpu;
> >       int addr_cells = 1;
> >       const MachineState *ms = MACHINE(vms);
> > +    const VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms);
> >       int smp_cpus = ms->smp.cpus;
> >   
> >       /*
> > -     * From Documentation/devicetree/bindings/arm/cpus.txt
> > +     *  See Linux Documentation/devicetree/bindings/arm/cpus.yaml
> >        *  On ARM v8 64-bit systems value should be set to 2,
> >        *  that corresponds to the MPIDR_EL1 register size.
> >        *  If MPIDR_EL1[63:32] value is equal to 0 on all CPUs
> > @@ -408,8 +409,45 @@ static void fdt_add_cpu_nodes(const VirtMachineState *vms)
> >                   ms->possible_cpus->cpus[cs->cpu_index].props.node_id);
> >           }
> >   
> > +        if (ms->smp.cpus > 1 && !vmc->no_cpu_topology) {
> We should probably always generate the cpu-map, like we agreed to always
> generate the PPTT.
Ok, I will remove smp.cpus check for cpu-map too.
Single cpu node, corresponding to single cpu-map path also works.
> If, for some reason, we don't want to generate the
> cpu-map for uniprocessor systems, then we should actually be checking
> ms->smp.maxcpus here (and below) to be sure it's uniprocessor.
Right, it's max cpus that ought to be checked but not smp cpus.

Thanks,
Yanan
> Thanks,
> drew
>
> > +            qemu_fdt_setprop_cell(ms->fdt, nodename, "phandle",
> > +                                  qemu_fdt_alloc_phandle(ms->fdt));
> > +        }
> > +
> >           g_free(nodename);
> >       }
> > +
> > +    if (ms->smp.cpus > 1 && !vmc->no_cpu_topology) {
> > +        /*
> > +         * See Linux Documentation/devicetree/bindings/cpu/cpu-topology.txt
> > +         * In a SMP system, the hierarchy of CPUs is defined through four
> > +         * entities that are used to describe the layout of physical CPUs
> > +         * in the system: socket/cluster/core/thread.
> > +         */
> > +        qemu_fdt_add_subnode(ms->fdt, "/cpus/cpu-map");
> > +
> > +        for (cpu = ms->smp.cpus - 1; cpu >= 0; cpu--) {
> > +            char *cpu_path = g_strdup_printf("/cpus/cpu@%d", cpu);
> > +            char *map_path;
> > +
> > +            if (ms->smp.threads > 1) {
> > +                map_path = g_strdup_printf(
> > +                    "/cpus/cpu-map/%s%d/%s%d/%s%d",
> > +                    "socket", cpu / (ms->smp.cores * ms->smp.threads),
> > +                    "core", (cpu / ms->smp.threads) % ms->smp.cores,
> > +                    "thread", cpu % ms->smp.threads);
> > +            } else {
> > +                map_path = g_strdup_printf(
> > +                    "/cpus/cpu-map/%s%d/%s%d",
> > +                    "socket", cpu / ms->smp.cores,
> > +                    "core", cpu % ms->smp.cores);
> > +            }
> > +            qemu_fdt_add_path(ms->fdt, map_path);
> > +            qemu_fdt_setprop_phandle(ms->fdt, map_path, "cpu", cpu_path);
> > +            g_free(map_path);
> > +            g_free(cpu_path);
> > +        }
> > +    }
> >   }
> >   
> >   static void fdt_add_its_gic_node(VirtMachineState *vms)
> > @@ -2769,6 +2807,7 @@ static void virt_machine_5_2_options(MachineClass *mc)
> >       virt_machine_6_0_options(mc);
> >       compat_props_add(mc->compat_props, hw_compat_5_2, hw_compat_5_2_len);
> >       vmc->no_secure_gpio = true;
> > +    vmc->no_cpu_topology = true;
> >   }
> >   DEFINE_VIRT_MACHINE(5, 2)
> >   
> > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> > index 921416f918..4a4b98e4a7 100644
> > --- a/include/hw/arm/virt.h
> > +++ b/include/hw/arm/virt.h
> > @@ -129,6 +129,7 @@ struct VirtMachineClass {
> >       bool no_kvm_steal_time;
> >       bool acpi_expose_flash;
> >       bool no_secure_gpio;
> > +    bool no_cpu_topology;
> >   };
> >   
> >   struct VirtMachineState {
> > --
> > 2.19.1
> .