From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) (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 99FFD2EACF6 for ; Thu, 26 Jun 2025 15:13:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750950791; cv=none; b=bS+zoP8V4bP+Eiy4m/C24XGmPKLndfH98lQGlPud94fpqG42+FIwF+Wu49B6njO13lMGzAq5nc8FsQjpEspOhrHQR4gZL2+YBtygI4H/ImIbeCMpU51vBIbx1m9aQc503Ilqfl+zC60kuQTp0paIiMJoocpd/aEABxz316Wdkd4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750950791; c=relaxed/simple; bh=3f3qxDKvxDl4HUf3HIbqzgM9/mI/iNDu+z+hney4Tq0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gixve7bh3B+aiXLIXDSOZ1vPhJMwPNXlzu+erj3XQ2QmOA0W2pFaCVnjQ42dcLZ36rct9HSpPjltcn63/wSnLLJzubrKt+UdhdYAmYDrCkGMu45wjzbJv5lM5p1YS1HDdI7OyHCEyl9jadId/B/5d3rda02NTtnBLS/YQY9qMpw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=ghG0PZyW; arc=none smtp.client-ip=209.85.128.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="ghG0PZyW" Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-451d41e1ad1so7542255e9.1 for ; Thu, 26 Jun 2025 08:13:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1750950788; x=1751555588; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:from:to:cc:subject:date:message-id:reply-to; bh=Sq8L/7jnSV6837VjO0hrxDQrv+5WbHPxhbytT6DZZLk=; b=ghG0PZyW9sxmwApYdhwqcZq2laRem4xdNhf4zmI00QlpufPBayN9ZiNdSgKi2AqJv7 3P8CoeGrlEAorqQh0uJQkRgPk6nSk4kZPOOriByRLk57dOLOsQAnP1EQKrfGAro1RK49 84H1z6n6OlVvG6AgzpihXvTyzqR62rZRNvdWnoOgyWxFZKxYCDWmASEvadzAmwpbPTiP GzAdimiSR2tn63TfUNy0puI1vTbTTnRSfCJP9bLNG04XNLXvlJt46iIgvDntRHKKIshW GmxYAZxKHysDsfN/qplcnTZ54a8hY9DkL8b/j2MVBwkQVWy4IRalJkvtO8peyhtboEVJ p3XA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750950788; x=1751555588; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=Sq8L/7jnSV6837VjO0hrxDQrv+5WbHPxhbytT6DZZLk=; b=LlaubpKXyuk6OZAzM/WRlrcguw/D1beSF4FgIVD+zfDvRuzvUZgjMxRpaeyV2MwRLe i+0Yo2IbTlNC05CP6qUYqT2hlBihXBv8jPU4UauJxiN9xPev/bVmOaK1AqHQ4pAqhlZt tc2Ovh8j3+xpsg2KzJVcA5PfpCCMWfPiEP8j1MKhzyZ67iPaU29QshvNjxuANT3KIfoz FuKK9f/TQRCNKdP5PnOrmROzcJq3/agsUswSf39t+78/8bB0IVhbznzELAbnGjK3BX3N EdPn8JgTj37GH4PmjUStDWKKk5zf7hTuHinVwL3DiRr7EHcN0uDreoR5BqRlMZ8gF/J1 SPiw== X-Forwarded-Encrypted: i=1; AJvYcCXSPtHaBhQyFZ6Jt+dJ1EnncDqeYu0cM4P/gLRg3HTGD1f1w766WxOYrh6tZHCbdQTomoFWcuolPQ8e5dU=@vger.kernel.org X-Gm-Message-State: AOJu0YwO/JxsCYxP51cJyDaqw9a8U4XdVDByOY1WawbDModEgfRiIwSW h+QVtmmDozK3gUdGpDEks1xISuFk8Pg4ER5bctG/G3Cr0mnsnxoEVEXR6Pr+oN69qdo= X-Gm-Gg: ASbGncs/mJAl63sb9OWAP+OYDctKWQSyeSSMbKytZmxURT2xqnYBOWqX8+jIe4yuDlp c83O1b0BOSlpIWd3EclWOZONMmHA2/pJgqyYO60Kn4tFN7BIQadxWFkx5XX29rv/gYXYQdwE7JZ 0Xijlpsh330yVr7jVlLGw1JiLl9OEeBLAfQITe8mb04N0hoiEUkHR9bRZF9f/d7e3C1Dd+KK+yB +8Bk1R2o2sxKPBDvwvsv8EQlF01sKsmXwnmasfD9O4vTBZ7jwYvPDLafV7TIUHfakIef4br3hVF z60TQRPJ8cgCVQsdZuFuIQtQYrEnOrqkDszAJaKKx1A1OGn5PhNfBA6IL//Zyp1vKeTUd338efd J X-Google-Smtp-Source: AGHT+IFPF71+mfSO9NvN0xkeypXe5O2hTFR0l2NynQYTObOWmXChzYdnye9o5T5yiOJKGSQbmmhpVA== X-Received: by 2002:a05:600c:1c29:b0:43b:ca39:6c75 with SMTP id 5b1f17b1804b1-4538875c58amr47054965e9.16.1750950787825; Thu, 26 Jun 2025 08:13:07 -0700 (PDT) Received: from [192.168.0.20] ([212.21.159.38]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4538a390bf8sm23178575e9.4.2025.06.26.08.13.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Jun 2025 08:13:07 -0700 (PDT) Message-ID: <295f94d4-f5e2-4849-ab62-9fdc75722e20@suse.com> Date: Thu, 26 Jun 2025 18:13:05 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] x86/bugs: Remove 'force' options for retbleed/ITS To: Peter Zijlstra , David Kaplan Cc: Thomas Gleixner , Borislav Petkov , Josh Poimboeuf , Pawan Gupta , Ingo Molnar , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org References: <20250626142703.716997-1-david.kaplan@amd.com> <20250626144047.GN1613200@noisy.programming.kicks-ass.net> From: Nikolay Borisov Content-Language: en-US Autocrypt: addr=nik.borisov@suse.com; keydata= xsFNBGcrpvIBEAD5cAR5+qu30GnmPrK9veWX5RVzzbgtkk9C/EESHy9Yz0+HWgCVRoNyRQsZ 7DW7vE1KhioDLXjDmeu8/0A8u5nFMqv6d1Gt1lb7XzSAYw7uSWXLPEjFBtz9+fBJJLgbYU7G OpTKy6gRr6GaItZze+r04PGWjeyVUuHZuncTO7B2huxcwIk9tFtRX21gVSOOC96HcxSVVA7X N/LLM2EOL7kg4/yDWEhAdLQDChswhmdpHkp5g6ytj9TM8bNlq9I41hl/3cBEeAkxtb/eS5YR 88LBb/2FkcGnhxkGJPNB+4Siku7K8Mk2Y6elnkOctJcDvk29DajYbQnnW4nhfelZuLNupb1O M0912EvzOVI0dIVgR+xtosp66bYTOpX4Xb0fylED9kYGiuEAeoQZaDQ2eICDcHPiaLzh+6cc pkVTB0sXkWHUsPamtPum6/PgWLE9vGI5s+FaqBaqBYDKyvtJfLK4BdZng0Uc3ijycPs3bpbQ bOnK9LD8TYmYaeTenoNILQ7Ut54CCEXkP446skUMKrEo/HabvkykyWqWiIE/UlAYAx9+Ckho TT1d2QsmsAiYYWwjU8igXBecIbC0uRtF/cTfelNGrQwbICUT6kJjcOTpQDaVyIgRSlUMrlNZ XPVEQ6Zq3/aENA8ObhFxE5PLJPizJH6SC89BMKF3zg6SKx0qzQARAQABzSZOaWtvbGF5IEJv cmlzb3YgPG5pay5ib3Jpc292QHN1c2UuY29tPsLBkQQTAQoAOxYhBDuWB8EJLBUZCPjT3SRn XZEnyhfsBQJnK6byAhsDBQsJCAcCAiICBhUKCQgLAgQWAgMBAh4HAheAAAoJECRnXZEnyhfs XbIQAJxuUnelGdXbSbtovBNm+HF3LtT0XnZ0+DoR0DemUGuA1bZAlaOXGr5mvVbTgaoGUQIJ 3Ejx3UBEG7ZSJcfJobB34w1qHEDO0pN9orGIFT9Bic3lqhawD2r85QMcWwjsZH5FhyRx7P2o DTuUClLMO95GuHYQngBF2rHHl8QMJPVKsR18w4IWAhALpEApxa3luyV7pAAqKllfCNt7tmed uKmclf/Sz6qoP75CvEtRbfAOqYgG1Uk9A62C51iAPe35neMre3WGLsdgyMj4/15jPYi+tOUX Tc7AAWgc95LXyPJo8069MOU73htZmgH4OYy+S7f+ArXD7h8lTLT1niff2bCPi6eiAQq6b5CJ Ka4/27IiZo8tm1XjLYmoBmaCovqx5y5Xt2koibIWG3ZGD2I+qRwZ0UohKRH6kKVHGcrmCv0J YO8yIprxgoYmA7gq21BpTqw3D4+8xujn/6LgndLKmGESM1FuY3ymXgj5983eqaxicKpT9iq8 /a1j31tms4azR7+6Dt8H4SagfN6VbJ0luPzobrrNFxUgpjR4ZyQQ++G7oSRdwjfIh1wuCF6/ mDUNcb6/kA0JS9otiC3omfht47yQnvod+MxFk1lTNUu3hePJUwg1vT1te3vO5oln8lkUo9BU knlYpQ7QA2rDEKs+YWqUstr4pDtHzwQ6mo0rqP+zzsFNBGcrpvIBEADGYTFkNVttZkt6e7yA LNkv3Q39zQCt8qe7qkPdlj3CqygVXfw+h7GlcT9fuc4kd7YxFys4/Wd9icj9ZatGMwffONmi LnUotIq2N7+xvc4Xu76wv+QJpiuGEfCDB+VdZOmOzUPlmMkcJc/EDSH4qGogIYRu72uweKEq VfBI43PZIGpGJ7TjS3THX5WVI2YNSmuwqxnQF/iVqDtD2N72ObkBwIf9GnrOgxEyJ/SQq2R0 g7hd6IYk7SOKt1a8ZGCN6hXXKzmM6gHRC8fyWeTqJcK4BKSdX8PzEuYmAJjSfx4w6DoxdK5/ 9sVrNzaVgDHS0ThH/5kNkZ65KNR7K2nk45LT5Crjbg7w5/kKDY6/XiXDx7v/BOR/a+Ryo+lM MffN3XSnAex8cmIhNINl5Z8CAvDLUtItLcbDOv7hdXt6DSyb65CdyY8JwOt6CWno1tdjyDEG 5ANwVPYY878IFkOJLRTJuUd5ltybaSWjKIwjYJfIXuoyzE7OL63856MC/Os8PcLfY7vYY2LB cvKH1qOcs+an86DWX17+dkcKD/YLrpzwvRMur5+kTgVfXcC0TAl39N4YtaCKM/3ugAaVS1Mw MrbyGnGqVMqlCpjnpYREzapSk8XxbO2kYRsZQd8J9ei98OSqgPf8xM7NCULd/xaZLJUydql1 JdSREId2C15jut21aQARAQABwsF2BBgBCgAgFiEEO5YHwQksFRkI+NPdJGddkSfKF+wFAmcr pvICGwwACgkQJGddkSfKF+xuuxAA4F9iQc61wvAOAidktv4Rztn4QKy8TAyGN3M8zYf/A5Zx VcGgX4J4MhRUoPQNrzmVlrrtE2KILHxQZx5eQyPgixPXri42oG5ePEXZoLU5GFRYSPjjTYmP ypyTPN7uoWLfw4TxJqWCGRLsjnkwvyN3R4161Dty4Uhzqp1IkNhl3ifTDYEvbnmHaNvlvvna 7+9jjEBDEFYDMuO/CA8UtoVQXjy5gtOhZZkEsptfwQYc+E9U99yxGofDul7xH41VdXGpIhUj 4wjd3IbgaCiHxxj/M9eM99ybu5asvHyMo3EFPkyWxZsBlUN/riFXGspG4sT0cwOUhG2ZnExv XXhOGKs/y3VGhjZeCDWZ+0ZQHPCL3HUebLxW49wwLxvXU6sLNfYnTJxdqn58Aq4sBXW5Un0Q vfbd9VFV/bKFfvUscYk2UKPi9vgn1hY38IfmsnoS8b0uwDq75IBvup9pYFyNyPf5SutxhFfP JDjakbdjBoYDWVoaPbp5KAQ2VQRiR54lir/inyqGX+dwzPX/F4OHfB5RTiAFLJliCxniKFsM d8eHe88jWjm6/ilx4IlLl9/MdVUGjLpBi18X7ejLz3U2quYD8DBAGzCjy49wJ4Di4qQjblb2 pTXoEyM2L6E604NbDu0VDvHg7EXh1WwmijEu28c/hEB6DwtzslLpBSsJV0s1/jE= In-Reply-To: <20250626144047.GN1613200@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/26/25 17:40, Peter Zijlstra wrote: > On Thu, Jun 26, 2025 at 09:27:03AM -0500, David Kaplan wrote: >> Command line options which force-enable a mitigation on an unaffected >> processor provide arguably no security value but do create the potential >> for problems due to the increased set of mitigation interactions. >> >> For example, setting "indirect_target_selection=force" on an AMD >> Retbleed-affected CPU (e.g., Zen2) results in a configuration where the >> kernel reports that both ITS and Retbleed are mitigated, but Retbleed is >> not in fact mitigated. In this configuration, untraining of the retbleed >> return thunk is enabled but the its_return_thunk is active, rendering the >> untraining ineffective. >> >> It is wrong for the kernel to report that a bug is mitigated when it is >> not. While this specific interaction could be directly fixed, the ability >> to force-enable these bugs creates unneeded complexity, so remove it. >> >> If removing these options entirely is unacceptable, perhaps for >> compatibility reasons, another option could be to only allow forcing on the >> affected vendor (i.e., only allow forcing ITS on Intel CPUs), which would >> at least limit the potential interactions that need to be analyzed. >> Tagging as RFC to prompt discussion on this point. > > Testing; I use these things for testing. Makes I don't have to run on > affected hardware, I can just force the feature on and inspect the code > and ensures it runs. > > If you use force, you get to keep all pieces -- no warranties. I concur, however using force won't always guarantee that the code runs though, because there can be other condition that must/must not be met i.e trying to run ITS on AMD hw (yeah, yeah I know :) ) also required commenting out some checks in patch_retpoline. >