From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 69ACF2D3745; Wed, 2 Jul 2025 17:12:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751476333; cv=none; b=jstQBhV5EFb84MFNn1Iu5HXXN1/PCcJvujgUlXDB8c1n3PMwjgZRRTi2/5RUU+rgLNlKwT/L6zuzDMte+3t8zlvy2gX7IDgVb2zNcR9MeuufdSySdKAUjAj15rbTdIzMcztvqLMyfNApeIO+YB45yF4l0D1IDT2L/D96P5wDW2g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751476333; c=relaxed/simple; bh=kNg/g5ljt7nOKC7WSIlXA9rxszXt9xhQVAALjJf2IYA=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=MnZ8vVppVsiuHXQ1esa2BucPlq2sZcQSX6sW8/FgPwQoqY/pq3d3Rrl0bY14XWUgIdBVnNN3pXJl9PgIa69aUaoti9rifAa+qlSNuhdiuPO8XRKyt9+kMRb7BbkWWPJWEf4GIfpT3Y/7V3v1Buj5htoxBi7Wtw78SG3m5nawu+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=Hjeif9o6; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="Hjeif9o6" Received: from [127.0.0.1] (c-76-133-66-138.hsd1.ca.comcast.net [76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 562HB06T746462 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Wed, 2 Jul 2025 10:11:00 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 562HB06T746462 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025062101; t=1751476264; bh=kNg/g5ljt7nOKC7WSIlXA9rxszXt9xhQVAALjJf2IYA=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=Hjeif9o6GyWihjdMk5Hc7VaQ50WO7uLC7HzqhSUd/55fcAhpCapeTKEfyaM12BtdP gz0aCmWronOAjPiG8PFmpiKZLUUgms/EB+TluNZQGC0t+htsKumiZnB19lwpJm1lxd XipDNLBIhgIcXXTJhTEB18mKX4956sMHLlVhGHa3qP/+Tiib0YjFSP0gCwRtwX3qxg H7VtggQXp62qQ8Jqi8JutBAsT2f6+dw6WmZeAyLVZxFy8adB2lc64rl5Z9r44BAKHM PNEhOVUevuJ8BvcGjrd/U9juT59nGLE4xRb5fFJw+aOnp+kFWiq/gGuEEHgXZCkIF+ GnxnsUEIyZMbQ== Date: Wed, 02 Jul 2025 10:10:58 -0700 From: "H. Peter Anvin" To: "Kirill A. Shutemov" CC: Sohil Mehta , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Peter Zijlstra , Ard Biesheuvel , "Paul E. McKenney" , Josh Poimboeuf , Xiongwei Song , Xin Li , "Mike Rapoport (IBM)" , Brijesh Singh , Michael Roth , Tony Luck , Alexey Kardashevskiy , Alexander Shishkin , Jonathan Corbet , Ingo Molnar , Pawan Gupta , Daniel Sneddon , Kai Huang , Sandipan Das , Breno Leitao , Rick Edgecombe , Alexei Starovoitov , Hou Tao , Juergen Gross , Vegard Nossum , Kees Cook , Eric Biggers , Jason Gunthorpe , "Masami Hiramatsu (Google)" , Andrew Morton , Luis Chamberlain , Yuntao Wang , Rasmus Villemoes , Christophe Leroy , Tejun Heo , Changbin Du , Huang Shijie , Geert Uytterhoeven , Namhyung Kim , Arnaldo Carvalho de Melo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv8 14/17] x86/traps: Handle LASS thrown #SS User-Agent: K-9 Mail for Android In-Reply-To: <6vihhfk5z33nrpy53ck2c6tkscjas4fhi6hqorenknbnjo4k3j@ywybd4obx76m> References: <20250701095849.2360685-1-kirill.shutemov@linux.intel.com> <20250701095849.2360685-15-kirill.shutemov@linux.intel.com> <95dc18fd-73b0-4019-92d2-c0e6aaf22c96@intel.com> <4DE45AFD-C1E0-4FB8-BE01-44A72C5C6E1E@zytor.com> <5q2zbkzyjknusd3feqolycqialetqfe52yfyzasnr6zp24pmej@4cg2r2hi4pf2> <6vihhfk5z33nrpy53ck2c6tkscjas4fhi6hqorenknbnjo4k3j@ywybd4obx76m> Message-ID: <498F5590-2711-47E9-A58F-CC9EB41D71AA@zytor.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On July 2, 2025 7:47:30 AM PDT, "Kirill A=2E Shutemov" wrote: >On Wed, Jul 02, 2025 at 07:37:12AM -0700, H=2E Peter Anvin wrote: >> A LASS violation of any kind in the kernel (unless handled by fixup, >> including user access fixup) ought to be fatal, correct? > >Yes, LASS violation is fatal for !user_mode(regs), unless addressed by >fixups=2E > >For user_mode(regs), emulate_vsyscall_gp() is the notable exception=2E > Note also that for FRED we can have separate kernel and user space paths b= asically "for free"=2E I'm not sure if we do that yet (if the infrastructur= e is there), but we could=2E=20 Not that it matters for this case=2E This is a slow path=2E