Re: [PATCH v3 2/2] riscv: topology: fix default topology reporting

From: <Conor.Dooley@microchip.com>
To: <sudeep.holla@arm.com>, <mail@conchuod.ie>
Cc: <paul.walmsley@sifive.com>, <palmer@dabbelt.com>,
	<palmer@rivosinc.com>, <aou@eecs.berkeley.edu>,
	<catalin.marinas@arm.com>, <will@kernel.org>,
	<gregkh@linuxfoundation.org>, <rafael@kernel.org>,
	<Daire.McNamara@microchip.com>, <niklas.cassel@wdc.com>,
	<damien.lemoal@opensource.wdc.com>, <geert@linux-m68k.org>,
	<zong.li@sifive.com>, <kernel@esmil.dk>, <hahnjo@hahnjo.de>,
	<guoren@kernel.org>, <anup@brainfault.org>,
	<atishp@atishpatra.org>, <heiko@sntech.de>,
	<philipp.tomsich@vrull.eu>, <robh@kernel.org>, <maz@kernel.org>,
	<viresh.kumar@linaro.org>, <linux-riscv@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>, <Brice.Goglin@inria.fr>
Subject: Re: [PATCH v3 2/2] riscv: topology: fix default topology reporting
Date: Mon, 11 Jul 2022 16:28:28 +0000	[thread overview]
Message-ID: <6f96ad4b-6901-d5fd-9d55-2da9bdc925c3@microchip.com> (raw)
In-Reply-To: <20220711145941.q5rdrtavstjkp3km@bogus>

On 11/07/2022 15:59, Sudeep Holla wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On Sat, Jul 09, 2022 at 04:23:55PM +0100, Conor Dooley wrote:
>> From: Conor Dooley <conor.dooley@microchip.com>
>>
>> RISC-V has no sane defaults to fall back on where there is no cpu-map
>> in the devicetree.
>> Without sane defaults, the package, core and thread IDs are all set to
>> -1. This causes user-visible inaccuracies for tools like hwloc/lstopo
>> which rely on the sysfs cpu topology files to detect a system's
>> topology.
>>
>> On a PolarFire SoC, which should have 4 harts with a thread each,
>> lstopo currently reports:
>>
>> Machine (793MB total)
>>   Package L#0
>>     NUMANode L#0 (P#0 793MB)
>>     Core L#0
>>       L1d L#0 (32KB) + L1i L#0 (32KB) + PU L#0 (P#0)
>>       L1d L#1 (32KB) + L1i L#1 (32KB) + PU L#1 (P#1)
>>       L1d L#2 (32KB) + L1i L#2 (32KB) + PU L#2 (P#2)
>>       L1d L#3 (32KB) + L1i L#3 (32KB) + PU L#3 (P#3)
>>
>> Adding calls to store_cpu_topology() in {boot,smp} hart bringup code
>> results in the correct topolgy being reported:
>>
>> Machine (793MB total)
>>   Package L#0
>>     NUMANode L#0 (P#0 793MB)
>>     L1d L#0 (32KB) + L1i L#0 (32KB) + Core L#0 + PU L#0 (P#0)
>>     L1d L#1 (32KB) + L1i L#1 (32KB) + Core L#1 + PU L#1 (P#1)
>>     L1d L#2 (32KB) + L1i L#2 (32KB) + Core L#2 + PU L#2 (P#2)
>>     L1d L#3 (32KB) + L1i L#3 (32KB) + Core L#3 + PU L#3 (P#3)
>>
>> CC: stable@vger.kernel.org
>> Fixes: 03f11f03dbfe ("RISC-V: Parse cpu topology during boot.")
>> Reported-by: Brice Goglin <Brice.Goglin@inria.fr>
>> Link: https://github.com/open-mpi/hwloc/issues/536
>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>> ---
>> ---
>>  arch/riscv/Kconfig          | 2 +-
>>  arch/riscv/kernel/smpboot.c | 4 +++-
>>  2 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 2af0701b7518..4b6c2fdbb57c 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -52,7 +52,7 @@ config RISCV
>>       select COMMON_CLK
>>       select CPU_PM if CPU_IDLE
>>       select EDAC_SUPPORT
>> -     select GENERIC_ARCH_TOPOLOGY if SMP
>> +     select GENERIC_ARCH_TOPOLOGY
> 
> I am not sure of !SMP as ARM64 is default SMP only. I have never reviewed
> the arch topology code with !SMP considered. I will leave that part to
> RISC-V developers.
> 

I checked it on a D1 which is !SMP - no trouble booting and
the topology reporting seemed fine.

Thanks for the reviews,
Conor.
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