linux-kernel - Re: [tip: x86/core] zstd: Increase DYNAMIC_BMI2 GCC version cutoff from 4.8 to 11.0 to work around compiler segfault

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Message-ID: <20250321124813.GAZ91gDUYB6TDsMJNv@fat_crate.local>
Date: Fri, 21 Mar 2025 13:48:13 +0100
From: Borislav Petkov <bp@...en8.de>
To: linux-kernel@...r.kernel.org, Nick Terrell <terrelln@...com>
Cc: linux-tip-commits@...r.kernel.org,
	Michael Kelley <mhklinux@...look.com>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org
Subject: Re: [tip: x86/core] zstd: Increase DYNAMIC_BMI2 GCC version cutoff
 from 4.8 to 11.0 to work around compiler segfault

(cleanup the botched CC: line :))

+ Nick.

Interesting - we were looking at a similar issue recently:

https://lore.kernel.org/r/20250317135539.GDZ9gp24DhTKBGmkd8@fat_crate.local

and upgrading my toolchain fixed it.

Weird.

On Fri, Mar 21, 2025 at 07:59:49AM -0000, tip-bot2 for Ingo Molnar wrote:
> The following commit has been merged into the x86/core branch of tip:
> 
> Commit-ID:     1400c87e6cac47eb243f260352c854474d9a9073
> Gitweb:        https://git.kernel.org/tip/1400c87e6cac47eb243f260352c854474d9a9073
> Author:        Ingo Molnar <mingo@...nel.org>
> AuthorDate:    Fri, 21 Mar 2025 08:38:43 +01:00
> Committer:     Ingo Molnar <mingo@...nel.org>
> CommitterDate: Fri, 21 Mar 2025 08:38:43 +01:00
> 
> zstd: Increase DYNAMIC_BMI2 GCC version cutoff from 4.8 to 11.0 to work around compiler segfault
> 
> Due to pending percpu improvements in -next, GCC9 and GCC10 are
> crashing during the build with:
> 
>     lib/zstd/compress/huf_compress.c:1033:1: internal compiler error: Segmentation fault
>      1033 | {
>           | ^
>     Please submit a full bug report,
>     with preprocessed source if appropriate.
>     See <file:///usr/share/doc/gcc-9/README.Bugs> for instructions.
> 
> The DYNAMIC_BMI2 feature is a known-challenging feature of
> the ZSTD library, with an existing GCC quirk turning it off
> for GCC versions below 4.8.
> 
> Increase the DYNAMIC_BMI2 version cutoff to GCC 11.0 - GCC 10.5
> is the last version known to crash.
> 
> Reported-by: Michael Kelley <mhklinux@...look.com>
> Debugged-by: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Cc: https://lore.kernel.org/r/SN6PR02MB415723FBCD79365E8D72CA5FD4D82@SN6PR02MB4157.namprd02.prod.outlook.com
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> ---
>  lib/zstd/common/portability_macros.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/zstd/common/portability_macros.h b/lib/zstd/common/portability_macros.h
> index 0e3b2c0..0dde8bf 100644
> --- a/lib/zstd/common/portability_macros.h
> +++ b/lib/zstd/common/portability_macros.h
> @@ -55,7 +55,7 @@
>  #ifndef DYNAMIC_BMI2
>    #if ((defined(__clang__) && __has_attribute(__target__)) \
>        || (defined(__GNUC__) \
> -          && (__GNUC__ >= 5 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 8)))) \
> +          && (__GNUC__ >= 11))) \
>        && (defined(__x86_64__) || defined(_M_X64)) \
>        && !defined(__BMI2__)
>    #  define DYNAMIC_BMI2 1

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette