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

[Sudeep Holla <sudeep.holla@arm.com>]

On Wed, Jul 06, 2022 at 09:43:02AM +0000, Conor.Dooley@microchip.com wrote:
> 
> 
> On 06/07/2022 10:21, Sudeep Holla wrote:
> > On Tue, Jul 05, 2022 at 11:03:54PM +0000, Conor.Dooley@microchip.com wrote:
> >>
> >>
> >> On 05/07/2022 21:33, Conor.Dooley@microchip.com 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@microchip.com>
> >>>>>
> >>>>> 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@arm.com>
> >>>>
> >>>> 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@microchip.com>
> >> 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@microchip.com>
> >>
> >> 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.
> 
> 
> Cool, I'll respin a v2 without this included then & get the series
> backported since this is user visible & will fix all existing supported
> platforms.
>

The DT /cpu-map is optional, so I don't think it needs to be backported.

> 
> I'll send the topology code changes separately to avoid it going
> forwards.

This on the other hand can be backported to fix userspace.

-- 
Regards,
Sudeep