linux-kernel - Re: [PATCH v2 0/7] selftests/nolibc: customize CROSS

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Date:   Mon, 14 Aug 2023 10:25:00 +0200
From:   Willy Tarreau <w@....eu>
To:     Zhangjin Wu <falcon@...ylab.org>
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        tanyuan@...ylab.org, thomas@...ch.de
Subject: Re: [PATCH v2 0/7] selftests/nolibc: customize CROSS_COMPILE for all
 supported architectures

On Mon, Aug 14, 2023 at 03:38:54PM +0800, Zhangjin Wu wrote:
> > On Sun, Aug 13, 2023 at 06:05:03PM +0800, Zhangjin Wu wrote:
> > > > I think that later I'll further extend XARCH with new variants to
> > > > support ARMv5 and Thumb2, because we have different code for this
> > > > and I continue to manually change the CFLAGS to test both.
> > > >
> > > 
> > > Ok, what about further add x86_64 as the default variant for x86 (like ppc for
> > > powerpc)? and then it is able to only resereve the variables for x86_64. I have
> > > prepared a patch for this goal in our new tinyconfig patchset, it will further
> > > avoid adding the same nolibc-test-x86.config and nolibc-test-x86_64.config.
> > 
> > I'm confused, x86 already defaults to x86_64, it's just that it depends
> > on the .config itself to figure whether to produce a 32- or 64-bit kernel.
> > But for example it starts qemu in 64-bit mode. Am I missing anything ?
> >
> 
> In kernel side, it is, but in our nolibc-test, we have added a copy of x86_64
> for x86:
> 
>     $ grep -E "_x86" tools/testing/selftests/nolibc/Makefile 
>     IMAGE_x86_64     = arch/x86/boot/bzImage
>     IMAGE_x86        = arch/x86/boot/bzImage
>     CROSS_COMPILE_x86_64    ?= x86_64-linux- x86_64-linux-gnu-
>     CROSS_COMPILE_x86       ?= x86_64-linux- x86_64-linux-gnu-
>     DEFCONFIG_x86_64     = defconfig
>     DEFCONFIG_x86        = defconfig
>     QEMU_ARCH_x86_64     = x86_64
>     QEMU_ARCH_x86        = x86_64
>     QEMU_ARGS_x86_64     = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
>     QEMU_ARGS_x86        = -M pc -append "console=ttyS0,9600 i8042.noaux panic=-1 $(TEST:%=NOLIBC_TEST=%)"
> 
> With 'XARCH', the "_x86" copy of them can be simply replaced with such a line:
> 
>      # configure default variants for target kernel supported architectures
>      XARCH_powerpc    = ppc
>     +XARCH_x86        = x86_64
>      XARCH            = $(or $(XARCH_$(ARCH)),$(ARCH))
> 
> And therefore, the future nolibc-test-x86_64.config is also enough for x86.
> 
> But I have seen the 'x86' exception in tools/include/nolibc/Makefile, just a
> confirm on if this replacement is ok.

Ah I thought you meant the opposite, i.e. that ppc did map to powerpc
that I was not seeing anywhere else. Yes we can probably do that and
remove the x86-specific lines later.

Willy