linux-kernel - Re: [PATCH 2/3] selftests/nolibc: use file driver for QEMU serial

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Message-ID: <20250620075126.GB22550@1wt.eu>
Date: Fri, 20 Jun 2025 09:51:26 +0200
From: Willy Tarreau <w@....eu>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Yoshinori Sato <ysato@...rs.osdn.me>, Rich Felker <dalias@...c.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        Shuah Khan <shuah@...nel.org>, linux-sh@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] selftests/nolibc: use file driver for QEMU serial

Hi Thomas,

On Mon, Jun 09, 2025 at 11:28:58AM +0200, Thomas Weißschuh wrote:
> For the test implementation of the SuperH architecture a second serial
> serial port needs to be used. Unfortunately the currently used 'stdio'
> driver does not support multiple serial ports at the same time.
> 
> Switch to the 'file' driver which does support multiple ports and is
> sufficient for the nolibc-test usecase.
> 
> Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> ---
>  tools/testing/selftests/nolibc/Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/nolibc/Makefile b/tools/testing/selftests/nolibc/Makefile
> index 22da78a4bfea0274f66abec319d34b3d2a2824ac..238acaa7bb06dcdbcadd9d3190c2de726e1a40b1 100644
> --- a/tools/testing/selftests/nolibc/Makefile
> +++ b/tools/testing/selftests/nolibc/Makefile
> @@ -315,12 +315,12 @@ kernel-standalone: initramfs | defconfig
>  
>  # run the tests after building the kernel
>  run: kernel initramfs.cpio
> -	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(IMAGE)" -initrd initramfs.cpio -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
> +	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(IMAGE)" -initrd initramfs.cpio -serial file:/dev/stdout $(QEMU_ARGS) > "$(CURDIR)/run.out"
>  	$(Q)$(REPORT) $(CURDIR)/run.out
>  
>  # re-run the tests from an existing kernel
>  rerun:
> -	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(IMAGE)" -initrd initramfs.cpio -serial stdio $(QEMU_ARGS) > "$(CURDIR)/run.out"
> +	$(Q)qemu-system-$(QEMU_ARCH) -display none -no-reboot -kernel "$(IMAGE)" -initrd initramfs.cpio -serial file:/dev/stdout $(QEMU_ARGS) > "$(CURDIR)/run.out"

I'm cautious every time we touch the -serial output after having faced
issues earlier when trying to use pipes. Here I think it's OK, however,
I'm wondering if "file:$(CURDIR)/run.out" wouldn't be clearer, and also
encourage future changes to stick to a file and avoid piping the output
to a filter command. No strong opinion though.

In any case: Acked-by: Willy Tarreau <w@....eu>

Thanks,
Willy