linux-kernel - Re: [PATCH] selftests/nolibc: fix sparc32 tests with -mcpu=v9

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Message-ID: <aVtr8vJd_683mqUO@1wt.eu>
Date: Mon, 5 Jan 2026 08:44:50 +0100
From: Willy Tarreau <w@....eu>
To: Thomas Weißschuh <linux@...ssschuh.net>
Cc: Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/nolibc: fix sparc32 tests with -mcpu=v9

Hi Thomas,

On Sun, Jan 04, 2026 at 11:14:13PM +0100, Thomas Weißschuh wrote:
> Since LLVM commit 39e30508a7f6 ("[Driver][Sparc] Default to -mcpu=v9 for
> 32-bit Linux/sparc64 (#109278)"), clang defaults to -mcpu=v9 for 32-bit
> SPARC builds. -mcpu=v9 generates instructions which are not recognized
> by qemu-sparc and qemu-system-sparc. Instead qemu-sparc32plus and
> qemu-system-sparc64 with a 64-bit kernel and CONFIG_COMPAT are needed.
>
> Rework the test setup so that -mcpu=v9 also works correctly.

Hmmm doesn't this mean that we're now unable to emit proper sparc32
instructions with this compiler ? I don't know which CPUs the kernel
still supports, but if it still supports these old SS-5, maybe we
should instead pass the correct -mcpu to clang so that it emits the
expected instructions, otherwise we're just hiding the regressing by
upgrading the test machine beyond what the kernel supports ? Of course
if they're no longer supported that's different, but I'm still seeing
traces of SparcStation5 in the code so I don't know what to think about
this.

Thanks,
Willy