linux-kernel - Re: [PATCH] MIPS: vpe-mt: provide a default 'physical

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Date:   Tue, 14 Feb 2023 08:40:01 +0100
From:   Philippe Mathieu-Daudé <philmd@...aro.org>
To:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org
Cc:     kernel test robot <lkp@...el.com>,
        Dengcheng Zhu <dzhu@...ecomp.com>,
        John Crispin <john@...ozen.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        linux-mips@...r.kernel.org, Qais Yousef <qyousef@...alina.io>
Subject: Re: [PATCH] MIPS: vpe-mt: provide a default 'physical_memsize'

Hi Randy,

On 14/2/23 02:09, Randy Dunlap wrote:
> When neither LANTIQ nor MIPS_MALTA is set, 'physical_memsize' is not
> declared. This causes the build to fail with:
> 
> mips-linux-ld: arch/mips/kernel/vpe-mt.o: in function `vpe_run':
> arch/mips/kernel/vpe-mt.c:(.text.vpe_run+0x280): undefined reference to `physical_memsize'
> 
> Fix this by declaring a 0-value physical_memsize with neither LANTIQ
> nor MIPS_MALTA is set, like LANTIQ does.
> 
> Fixes: 1a2a6d7e8816 ("MIPS: APRP: Split VPE loader into separate files.")
> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
> Reported-by: kernel test robot <lkp@...el.com>
> Link: https://lore.kernel.org/all/202302030625.2g3E98sY-lkp@intel.com/
> Cc: Dengcheng Zhu <dzhu@...ecomp.com>
> Cc: John Crispin <john@...ozen.org>
> Cc: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
> Cc: linux-mips@...r.kernel.org
> ---
> How has this build error not been detected for 10 years?
> 
>   arch/mips/kernel/vpe-mt.c |    9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff -- a/arch/mips/kernel/vpe-mt.c b/arch/mips/kernel/vpe-mt.c
> --- a/arch/mips/kernel/vpe-mt.c
> +++ b/arch/mips/kernel/vpe-mt.c
> @@ -22,6 +22,15 @@ static int major;
>   /* The number of TCs and VPEs physically available on the core */
>   static int hw_tcs, hw_vpes;
>   
> +#if !defined(CONFIG_MIPS_MALTA) && !defined(CONFIG_LANTIQ)
> +/* The 2 above provide their own 'physical_memsize' variable. */

Which seems dubious. The variable should be defined once, likely in
arch/mips/kernel/vpe-mt.c, since arch/mips/include/asm/vpe.h declares
it.

I'm surprised CONFIG_MIPS_MALTA always links malta-dtshim.o, but
malta-dtshim.o depends on MIPS_VPE_LOADER_MT, and I can't find a
CONFIG_MIPS_MALTA -> MIPS_VPE_LOADER_MT Kconfig dep.

> +/*
> + * This is needed by the vpe-mt loader code, just set it to 0 and assume
> + * that the firmware hardcodes this value to something useful.
> + */
> +unsigned long physical_memsize = 0L;

I agree this is where this variable has be be declared / initialized,
but having this dependent on CONFIG_MIPS_MALTA/CONFIG_LANTIQ machines
doesn't seem right.

> +#endif
> +
>   /* We are prepared so configure and start the VPE... */
>   int vpe_run(struct vpe *v)
>   {

Regards,

Phil.