linux-kernel - Re: [PATCH] MIPS: generic: enable SMP on SMVP systems

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Message-ID: <e570866957f677aab77f2ecb48befc0dcc4481f4.camel@svanheule.net>
Date:   Sat, 18 Dec 2021 10:36:35 +0100
From:   Sander Vanheule <sander@...nheule.net>
To:     Jiaxun Yang <jiaxun.yang@...goat.com>, linux-mips@...r.kernel.org
Cc:     Paul Burton <paulburton@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-kernel@...r.kernel.org,
        INAGAKI Hiroshi <musashino.open@...il.com>
Subject: Re: [PATCH] MIPS: generic: enable SMP on SMVP systems

Hi Jiaxun,

On Fri, 2021-12-17 at 22:12 +0000, Jiaxun Yang wrote:
> 
> 
> 在 2021/12/17 18:39, Sander Vanheule 写道:
> > In addition to CPS SMP setups, also try to initialise MT SMP setups with
> > multiple VPEs per CPU core. CMP SMP support is not provided as it is
> > considered deprecated.
> > 
> > Additionally, rework the code by dropping the err variable and make it
> > similar to how other platforms perform this initialisation.
> Hi,
> 
> Thanks for your patch :-)
> 
> However there is a probem that register_vsmp_smp_ops never returns error
> if CONFIG_MIPS_MT_SMP is enabled. But generic kernel is supposed to
> run on systems with & without MT.
> 
> So probably you need:
> 
> diff --git a/arch/mips/include/asm/smp-ops.h 
> b/arch/mips/include/asm/smp-ops.h
> index 65618ff1280c..864aea803984 100644
> --- a/arch/mips/include/asm/smp-ops.h
> +++ b/arch/mips/include/asm/smp-ops.h
> @@ -101,6 +101,9 @@ static inline int register_vsmp_smp_ops(void)
>   #ifdef CONFIG_MIPS_MT_SMP
>          extern const struct plat_smp_ops vsmp_smp_ops;
> 
> +       if (!cpu_has_mipsmt)
> +               return -ENODEV;
> +
>          register_smp_ops(&vsmp_smp_ops);
> 
>          return 0;


Thanks for the feedback, I was wondering if we had missed something :)
I'll send a v2 (series) including this addition.

Best,
Sander