Re: [PATCH 0/5] RISC-V: Add cpu-map topology information nodes

[Sudeep Holla]

On Tue, Jul 05, 2022 at 11:03:54PM +0000, Conor.Dooley@xxxxxxxxxxxxx wrote:
> 
> 
> On 05/07/2022 21:33, Conor.Dooley@xxxxxxxxxxxxx wrote:
> > 
> > 
> > On 05/07/2022 21:19, Sudeep Holla wrote:
> >> On Tue, Jul 05, 2022 at 08:04:31PM +0100, Conor Dooley wrote:
> >>> From: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> >>>
> >>> It was reported to me that the Hive Unmatched incorrectly reports
> >>> its topology to hwloc, but the StarFive VisionFive did in [0] &
> >>> a subsequent off-list email from Brice (the hwloc maintainer).
> >>> This turned out not to be entirely true, the /downstream/ version
> >>> of the VisionFive does work correctly but not upstream, as the
> >>> downstream devicetree has a cpu-map node that was added recently.
> >>>
> >>> This series adds a cpu-map node to all upstream devicetrees, which
> >>> I have tested on mpfs & fu540. The first patch is lifted directly
> >>> from the downstream StarFive devicetree.
> >>>
> >>
> >> Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> >>
> >> I would recommend to have sane defaults in core risc-v code in case of
> >> absence of /cpu-map node as it is optional. The reason I mentioned is that
> >> Conor mentioned how the default values in absence of the node looked quite
> >> wrong. I don't know if it is possible on RISC-V but on ARM64 we do have
> >> default values if arch_topology fails to set based on DT/ACPI.
> >>
> > 
> > Yeah the defaults are all -1. I'll add some sane defaults for a v2.
> > Thanks,
> > Conor.
> 
> I shamelessly stole from arm64... Seems to work, but have done minimal
> testing (only PolarFire SoC).
> 
> Author: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> Date:   Wed Jul 6 00:00:34 2022 +0100
> 
>     riscv: arch-topology: add sane defaults
>     
>     RISC-V has no sane defaults to fall back on where there is no cpu-map
>     in the devicetree. Add sane defaults in ~the exact same way as ARM64.
>     
>     Signed-off-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>
> 
> diff --git a/arch/riscv/include/asm/topology.h b/arch/riscv/include/asm/topology.h
> new file mode 100644
> index 000000000000..71c80710f00e
> --- /dev/null
> +++ b/arch/riscv/include/asm/topology.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2022 Microchip Technology Inc. and its subsidiaries
> + */
> +
> +#ifndef _ASM_RISCV_TOPOLOGY_H
> +#define _ASM_RISCV_TOPOLOGY_H
> +
> +#include <asm-generic/topology.h>
> +
> +void store_cpu_topology(unsigned int cpuid);
> +
> +#endif /* _ASM_RISCV_TOPOLOGY_H */
> \ No newline at end of file
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index c71d6591d539..9518882ba6f9 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -50,6 +50,7 @@ obj-y += riscv_ksyms.o
>  obj-y  += stacktrace.o
>  obj-y  += cacheinfo.o
>  obj-y  += patch.o
> +obj-y  += topology.o
>  obj-y  += probes/
>  obj-$(CONFIG_MMU) += vdso.o vdso/
>  
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index f1e4948a4b52..d551c7f452d4 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -32,6 +32,7 @@
>  #include <asm/sections.h>
>  #include <asm/sbi.h>
>  #include <asm/smp.h>
> +#include <asm/topology.h>
>  
>  #include "head.h"
>  
> @@ -40,6 +41,8 @@ static DECLARE_COMPLETION(cpu_running);
>  void __init smp_prepare_boot_cpu(void)
>  {
>         init_cpu_topology();
> +
> +       store_cpu_topology(smp_processor_id());
>  }
>  
>  void __init smp_prepare_cpus(unsigned int max_cpus)
> @@ -161,6 +164,7 @@ asmlinkage __visible void smp_callin(void)
>         mmgrab(mm);
>         current->active_mm = mm;
>  
> +       store_cpu_topology(curr_cpuid);
>         notify_cpu_starting(curr_cpuid);
>         numa_add_cpu(curr_cpuid);
>         update_siblings_masks(curr_cpuid);
> diff --git a/arch/riscv/kernel/topology.c b/arch/riscv/kernel/topology.c
> new file mode 100644
> index 000000000000..799b3423e0bc
> --- /dev/null
> +++ b/arch/riscv/kernel/topology.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Based on the arm64 version, which was in turn based on arm32, which was
> + * ultimately based on sh's.
> + * The arm64 version was listed as:
> + * Copyright (C) 2011,2013,2014 Linaro Limited.
> + *
> + */
> +#include <linux/arch_topology.h>
> +#include <linux/topology.h>
> +#include <asm/topology.h>
> +
> +void store_cpu_topology(unsigned int cpuid)
> +{
> +       struct cpu_topology *cpuid_topo = &cpu_topology[cpuid];
> +
> +       if (cpuid_topo->package_id != -1)
> +               goto topology_populated;
> +
> +       cpuid_topo->thread_id = -1;
> +       cpuid_topo->core_id = cpuid;
> +       cpuid_topo->package_id = cpu_to_node(cpuid);
> +
> +       pr_info("CPU%u: cluster %d core %d thread %d\n",
> +                cpuid, cpuid_topo->package_id, cpuid_topo->core_id,
> +                cpuid_topo->thread_id);
> +
> +topology_populated:
> +       update_siblings_masks(cpuid);
> +}
>

Looks good. Again package id is not cluster. This is what my series is
addressing. So update the log as Package instead of Cluster above. The
cluster id will be -1 unless you can get that for DT.


-- 
Regards,
Sudeep