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From: Matt Fleming <matt@readmodwrite.com>
To: Borislav Petkov <bp@alien8.de>
Cc: "Rik van Riel" <riel@surriel.com>,
	"Henrik Böving" <henrik@lean-fro.org>,
	dave.hansen@linux.intel.com, luto@kernel.org,
	peterz@infradead.org, linux-kernel@vger.kernel.org,
	"Sebastian Ullrich" <sebastian@lean-fro.org>,
	"Joscha Mennicken" <joscha@lean-fro.org>,
	kernel-team@cloudflare.com
Subject: Re: PROBLEM: Probabilistic segfault on AMD hardware with INVLPGB
Date: Thu, 9 Jul 2026 08:21:55 +0100	[thread overview]
Message-ID: <ak9HSPvRDL7uNzI6@matt-Precision-5490> (raw)
In-Reply-To: <20260708161739.GAak54I-I0n5Pt_vAY@fat_crate.local>

On Wed, Jul 08, 2026 at 09:17:39AM -0700, Borislav Petkov wrote:
> Hey man,
> 
> what's up?
> 
> I see you're having fun. :-P
 
Hey! Yep, you know me mate... slightest whiff of a CPU bug and I'm there ;-)

> On Tue, Jul 07, 2026 at 01:18:30PM +0100, Matt Fleming wrote:
> > Hi Rik and Henrik,
> > 
> > I've got a small C reproducer that triggers this within the first round
> > on Cloudflare's AMD Turin machines:
> > 
> >   https://gist.github.com/mfleming/ca26ad3f8d65a12d23d62fb176480fc1
> > 
> > Build:
> > 
> >   gcc -O2 -Wall -Wextra -pthread -static -o repro-invlpgb repro-invlpgb.c
> 
> You need to have -std=c11 here on Debian-based systems because it says
> 
> repro-invlpgb.c:94:30: error: implicit declaration of function ‘ATOMIC_VAR_INIT’; did you mean ‘ATOMIC_FLAG_INIT’? [-Wimplicit-function-declaration]
>    94 | static atomic_bool running = ATOMIC_VAR_INIT(true);
> 
> here due to not "seeing" the stdatomic.h include. I guess atomics are a C11
> thing... :)

Thanks! I guess Ubuntu's GCC defaults masked this.

  reply	other threads:[~2026-07-09  7:21 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-06-19 13:17 PROBLEM: Probabilistic segfault on AMD hardware with INVLPGB Henrik Böving
2026-06-22 19:00 ` Rik van Riel
2026-06-23 12:28   ` Henrik Böving
2026-06-23 13:47     ` Andrew Cooper
2026-06-23 15:59     ` Rik van Riel
2026-07-07 12:18       ` Matt Fleming
2026-07-07 13:45         ` Henrik Böving
2026-07-07 14:11         ` Rik van Riel
2026-07-08 14:51           ` Dave Hansen
2026-07-07 16:44         ` Rik van Riel
2026-07-08 15:27         ` Rik van Riel
2026-07-08 15:51           ` Borislav Petkov
2026-07-08 16:17         ` Borislav Petkov
2026-07-09  7:21           ` Matt Fleming [this message]
2026-07-09 19:17             ` Borislav Petkov

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