From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f48.google.com (mail-ej1-f48.google.com [209.85.218.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B8E13D75CE for ; Tue, 7 Jul 2026 12:18:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783426715; cv=none; b=PS1aHiWTLSq1m76deY/Sm8BjHoY96sfM9ALeKsgLNqy/xRTFTVhNyqbGaSFy9jvfzJG2oRGpSUcSlTyysBJX2mqY7bCbtds8zN5f5sGdL8ILl7jC/TdGjT9EuXz6+lR0JxiUhp04ZLky2HN3FYP5JlfvyqVecampZ95399iwHUM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783426715; c=relaxed/simple; bh=JiqpGUBprpouYk9fQZ7boBmIQuOZ1lAB6yNR9E7CbbM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tpmEiupw3H4MbC1bSzXCWLXuhXQK4pPQ4aHe07O2P3AW8yEATw1sF4HeGhNgnDlJuyEdDDq2fT8S3GI97Zc9NICOFWxeVH4jABtEdr9osudDyRkGXnECjfSdxY+b1byZk7UCxfQygX/Fmynpcb14UnrSpdTvMWEsnw06UElMrvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=readmodwrite.com; spf=none smtp.mailfrom=readmodwrite.com; dkim=pass (2048-bit key) header.d=readmodwrite-com.20251104.gappssmtp.com header.i=@readmodwrite-com.20251104.gappssmtp.com header.b=z+Dip7hx; arc=none smtp.client-ip=209.85.218.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=readmodwrite.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=readmodwrite.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=readmodwrite-com.20251104.gappssmtp.com header.i=@readmodwrite-com.20251104.gappssmtp.com header.b="z+Dip7hx" Received: by mail-ej1-f48.google.com with SMTP id a640c23a62f3a-c127813835aso484615366b.2 for ; Tue, 07 Jul 2026 05:18:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=readmodwrite-com.20251104.gappssmtp.com; s=20251104; t=1783426712; x=1784031512; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=wiBrSWVeOljXZOZBmeB5jTrYnq9h+ZNVgQca6JOAJ0E=; b=z+Dip7hxYKpvcC0m+jrK/xp0dTSL1mqkZml6Q3AxV4gbvkDKGWPrsJ6U+yT4APjq8Z A9vspq8rpdiIaDbP21Bp3SDGKwifyOy1MJWgX0LJt6NkoM7p4wF4dMZxw/2Ot9oQbD4l XhtvQ3kPJ9FNByIIJNfNDqoWxKVZLMaAe4OiX0GKC67OyPPElA3Lr5PxCIbadqpu6eLH b8WkmgX+dkF819nqXxIlPyvGrGI2rAQBTBmjS+s3OtLYuRwopfpGja5IulhM1eC0HMI0 v1PC6s9a4ox02CSdexB2dFbVj2p6XBbklvi7mnr9jSMcreB99U0aylDpQghhpHQV7t2U Iqug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1783426712; x=1784031512; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=wiBrSWVeOljXZOZBmeB5jTrYnq9h+ZNVgQca6JOAJ0E=; b=CI4D2p3KncctSFVi8EvvmjSLfy0xLQCCcdQ81YtrHcCYBtZpPeWvQoe95wV0UKTgkE 3wThT8TuxSS+7KKeJ133j/s7yLuHjMjiPVHgxqBJazjLMCwk7v/biZbZbdDBvljLPJ6+ 5UckciNP16sCdeMA0gTOvPU+MEAXCuLr23tA1p1d0iLj7cbJihioiEsNsZAjSijb5iGd G/NMa47leaNkzSrGOpZM7EMlDIE/dCnRBY5AuysLdjSiXmMabaCc1yrnohQwUt8B7np1 0JkOHBL4G4Y882V7LeGQColAHpf/uFqWl7QV/bUWnFRzbHlsPoTPiYwuEVEGh/Fg1lfj xJUg== X-Forwarded-Encrypted: i=1; AHgh+RrF5mxpVJu8n+Vzx/X/AhMNO8M/z+4cLrI0NWP0dohHc+Yg1uhBxsbfggO7IuT07fg/FZTkliBAuz+BZQA=@vger.kernel.org X-Gm-Message-State: AOJu0YxN8EP3fw9y+zbrDjUg5EBY1cS6OXSE75l9ZWojjjSqx5mLDV5K 2YcXR4gxqfesGiA4Jp2Ij5uETmE187sK/Or8MpNSOl2yQ+1bEcvSaKFVS4KlQECozXU= X-Gm-Gg: AfdE7cmNmQQsGY+xr7ncZUVZ0+hKbD5/FKC58X4MIc+xRd0pcIvB4sPASzujTx8ngtw mVfK3UeKSymGnMSGYkDxPgfY17C/5UnDl/21ikyRnl0GD4XwZoUc/z7tw2paGDs9CvNXtcommzQ qE9BW0snCImj1NMkFvbDlqg8IC7LZKzRgN1v1YshiBvat8JtIM8R22Uf5/sN/kWrQWDKfYHWrVu xepXYAEHLhE/euDbgVy2W61v3g5pbMHRw8kZE8fbAohoEJH4JJrd7HnnCtWLCS+hTwga9kIqPXn EwVahoiRZeOo5YIsUm8XgW0hyQY7S33dmtIbKDD5NkUCkssSYV1SdyJHswM0nRcSki/9/ZQihnk gFjKcdo1RE7W/Xat0Ta+lLLtKiza9UiHUqqycSUh2Wx+3F+CHE5qynZ6wIjxpyqhw716eGbOGW5 A= X-Received: by 2002:a17:906:846e:b0:c12:8fe9:3a42 with SMTP id a640c23a62f3a-c15a68ea911mr174317566b.35.1783426712350; Tue, 07 Jul 2026 05:18:32 -0700 (PDT) Received: from localhost ([2a09:bac6:37a8:2696::3d8:22]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-c15ad84c636sm120848166b.22.2026.07.07.05.18.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 07 Jul 2026 05:18:31 -0700 (PDT) Date: Tue, 7 Jul 2026 13:18:30 +0100 From: Matt Fleming To: Rik van Riel Cc: Henrik =?utf-8?Q?B=C3=B6ving?= , dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, Sebastian Ullrich , Joscha Mennicken , kernel-team@cloudflare.com Subject: Re: PROBLEM: Probabilistic segfault on AMD hardware with INVLPGB Message-ID: References: <9363eca429424d967052bc401d4d835f1e6d2716.camel@surriel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Run: ./repro-invlpgb --batch --rounds 20 --jobs 32 -d 5 -w 8 -m 2 -s 512 -q The mutator side holds a pthread rwlock write lock while doing munmap() + mmap(MAP_FIXED) on the same VA and filling the range with {cookie, slot, generation, offset} markers. Reader threads hold the read lock while checking those markers. The failure mode is usually a CORRUPTION line rather than a direct SIGSEGV: a read from one virtual offset returns a valid marker for a different offset. That looks consistent with a stale or wrong translation after VA reuse. Thanks, Matt