From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 823A0C02183 for ; Fri, 17 Jan 2025 23:41:44 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.874351.1285066 (Exim 4.92) (envelope-from ) id 1tYvxw-0006Je-NL; Fri, 17 Jan 2025 23:41:28 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 874351.1285066; Fri, 17 Jan 2025 23:41:28 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1tYvxw-0006JX-KP; Fri, 17 Jan 2025 23:41:28 +0000 Received: by outflank-mailman (input) for mailman id 874351; Fri, 17 Jan 2025 23:41:28 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1tYvxv-0006JR-Um for xen-devel@lists.xenproject.org; Fri, 17 Jan 2025 23:41:27 +0000 Received: from mail-wm1-x32b.google.com (mail-wm1-x32b.google.com [2a00:1450:4864:20::32b]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 903a99ad-d52c-11ef-a0e2-8be0dac302b0; Sat, 18 Jan 2025 00:41:25 +0100 (CET) Received: by mail-wm1-x32b.google.com with SMTP id 5b1f17b1804b1-4361f664af5so28712845e9.1 for ; Fri, 17 Jan 2025 15:41:25 -0800 (PST) Received: from [192.168.1.10] (host-92-26-98-202.as13285.net. [92.26.98.202]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-438904084e7sm48317705e9.6.2025.01.17.15.41.24 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 17 Jan 2025 15:41:24 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 903a99ad-d52c-11ef-a0e2-8be0dac302b0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1737157285; x=1737762085; darn=lists.xenproject.org; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:from:to:cc:subject:date:message-id:reply-to; bh=7G+q7+YNodUeSCykRUjbKao1Cp6MRoZwAU9NzKs+V2Y=; b=fhy8Aka7FZ9cFtHYwDjJKS+FECbDjOv0kZEQI1EQE+x3P5+/9F6FSxU8MdBZaZm8y8 uJdxIVGiChE4M6b2iAtjVdQ7vMwFJQZlp/KwPNuh9yfKjoTn74+ZeTEM5Fk6Ub7T6fMt En3tqw8ZPThBuuEod4+Yrp8HOFE8e1dEwhdgk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737157285; x=1737762085; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language: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=7G+q7+YNodUeSCykRUjbKao1Cp6MRoZwAU9NzKs+V2Y=; b=KbkjqJBTRffsEvDutA+PwXAZTZ38YpAK2cWkNSpgCf4b3a58xzP8jQ5/L5xvi3a1pz WuRrnWIXLb+D2hFF12ZBgFct75cyzNAHmw3+F3JEZVvHgCO4fbzgOVUHcN1FLtKzX1N0 WvU3fJgVfRCMuWgTY9w4TFsTmd/wOUQUwAYPrGbG97V0BT6kEXFrsNM9S4399YJTxYpv X+oRmYubpvpfo4RE75Y0RqoVhxH7CdHeOdVyYNy4t1l/GF7SYrAx7fUUye2W/UOzoXZH zYBQIldjwYxxDN4gJLlLw0FJJV34t63CZcgYfxtuk/fkfZcTnzpnnbSVdvOaEfsmE3Es rMbQ== X-Forwarded-Encrypted: i=1; AJvYcCVTeFCu2pBtKnKpjDXT1m432xSjOka4DEvahuTKeVincxU6VnEBaBx6yZsRYGz+3EzpSpbA3xvCWbY=@lists.xenproject.org X-Gm-Message-State: AOJu0YznaBKFxMvVSpJO3Pbc+MGb0MAnfa7EHl0QRXWkFiXrrtE4m+96 vYvdXBL60Efj2xOZvy/AYid9kUdafOa8WnGSoSM9AWNhzFY0KtjhTqrIqh4MGBQ= X-Gm-Gg: ASbGncuB5wEYoTyoByTyMZx/AeJehJufFHp5FbHIKycFbZ3TGqUhPqXoAdVes1G1t+b hEgWaOHNCQGjoG+EvjRWq/RVNYhnxM7vDAinvKsoDGSdPC9MmEvWlkkQTEW7Z0iqBFeYZJz2hVK tvx55/Ls5SP30zol68QLb5Z+/HC5SvhCgf8wGA8Hj5ukFTD1Ib9wXqae22MvuGKufm2yp8yiGcJ nbag6Ez25g2n2250xs5JHQnG5+TycvfKGPM39OVVCAREb0cyI4N+KLWE/+cdGlK3Pe+w6uXzmFC F97Jm41QfVe0GlwYAgmY6m/LCVdGD/TfaQ== X-Google-Smtp-Source: AGHT+IHe/sgsUcek+Vt3Nw04aT02txb4V9vNV2R/6qTKuS/gvdVvsjV+LIMdtfyg/XFfOpBWB9KFmg== X-Received: by 2002:a05:600c:3ba7:b0:435:172:5052 with SMTP id 5b1f17b1804b1-438913becb8mr36689365e9.1.1737157284922; Fri, 17 Jan 2025 15:41:24 -0800 (PST) Message-ID: Date: Fri, 17 Jan 2025 23:41:24 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] x86: provide an inverted Kconfig control for shim-exclusive mode To: Stefano Stabellini , Jan Beulich Cc: Alejandro Vallejo , "xen-devel@lists.xenproject.org" , Julien Grall , Wei Liu , sergiy_kibrik@epam.com, =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= References: <617842e1-8ef2-b095-0c52-c2e2e5f1c0a8@suse.com> <6285f86d-f2d2-4040-999d-01aed3e72a36@suse.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; keydata= xsFNBFLhNn8BEADVhE+Hb8i0GV6mihnnr/uiQQdPF8kUoFzCOPXkf7jQ5sLYeJa0cQi6Penp VtiFYznTairnVsN5J+ujSTIb+OlMSJUWV4opS7WVNnxHbFTPYZVQ3erv7NKc2iVizCRZ2Kxn srM1oPXWRic8BIAdYOKOloF2300SL/bIpeD+x7h3w9B/qez7nOin5NzkxgFoaUeIal12pXSR Q354FKFoy6Vh96gc4VRqte3jw8mPuJQpfws+Pb+swvSf/i1q1+1I4jsRQQh2m6OTADHIqg2E ofTYAEh7R5HfPx0EXoEDMdRjOeKn8+vvkAwhviWXTHlG3R1QkbE5M/oywnZ83udJmi+lxjJ5 YhQ5IzomvJ16H0Bq+TLyVLO/VRksp1VR9HxCzItLNCS8PdpYYz5TC204ViycobYU65WMpzWe LFAGn8jSS25XIpqv0Y9k87dLbctKKA14Ifw2kq5OIVu2FuX+3i446JOa2vpCI9GcjCzi3oHV e00bzYiHMIl0FICrNJU0Kjho8pdo0m2uxkn6SYEpogAy9pnatUlO+erL4LqFUO7GXSdBRbw5 gNt25XTLdSFuZtMxkY3tq8MFss5QnjhehCVPEpE6y9ZjI4XB8ad1G4oBHVGK5LMsvg22PfMJ ISWFSHoF/B5+lHkCKWkFxZ0gZn33ju5n6/FOdEx4B8cMJt+cWwARAQABzSlBbmRyZXcgQ29v cGVyIDxhbmRyZXcuY29vcGVyM0BjaXRyaXguY29tPsLBegQTAQgAJAIbAwULCQgHAwUVCgkI CwUWAgMBAAIeAQIXgAUCWKD95wIZAQAKCRBlw/kGpdefoHbdD/9AIoR3k6fKl+RFiFpyAhvO 59ttDFI7nIAnlYngev2XUR3acFElJATHSDO0ju+hqWqAb8kVijXLops0gOfqt3VPZq9cuHlh IMDquatGLzAadfFx2eQYIYT+FYuMoPZy/aTUazmJIDVxP7L383grjIkn+7tAv+qeDfE+txL4 SAm1UHNvmdfgL2/lcmL3xRh7sub3nJilM93RWX1Pe5LBSDXO45uzCGEdst6uSlzYR/MEr+5Z JQQ32JV64zwvf/aKaagSQSQMYNX9JFgfZ3TKWC1KJQbX5ssoX/5hNLqxMcZV3TN7kU8I3kjK mPec9+1nECOjjJSO/h4P0sBZyIUGfguwzhEeGf4sMCuSEM4xjCnwiBwftR17sr0spYcOpqET ZGcAmyYcNjy6CYadNCnfR40vhhWuCfNCBzWnUW0lFoo12wb0YnzoOLjvfD6OL3JjIUJNOmJy RCsJ5IA/Iz33RhSVRmROu+TztwuThClw63g7+hoyewv7BemKyuU6FTVhjjW+XUWmS/FzknSi dAG+insr0746cTPpSkGl3KAXeWDGJzve7/SBBfyznWCMGaf8E2P1oOdIZRxHgWj0zNr1+ooF /PzgLPiCI4OMUttTlEKChgbUTQ+5o0P080JojqfXwbPAyumbaYcQNiH1/xYbJdOFSiBv9rpt TQTBLzDKXok86M7BTQRS4TZ/ARAAkgqudHsp+hd82UVkvgnlqZjzz2vyrYfz7bkPtXaGb9H4 Rfo7mQsEQavEBdWWjbga6eMnDqtu+FC+qeTGYebToxEyp2lKDSoAsvt8w82tIlP/EbmRbDVn 7bhjBlfRcFjVYw8uVDPptT0TV47vpoCVkTwcyb6OltJrvg/QzV9f07DJswuda1JH3/qvYu0p vjPnYvCq4NsqY2XSdAJ02HrdYPFtNyPEntu1n1KK+gJrstjtw7KsZ4ygXYrsm/oCBiVW/OgU g/XIlGErkrxe4vQvJyVwg6YH653YTX5hLLUEL1NS4TCo47RP+wi6y+TnuAL36UtK/uFyEuPy wwrDVcC4cIFhYSfsO0BumEI65yu7a8aHbGfq2lW251UcoU48Z27ZUUZd2Dr6O/n8poQHbaTd 6bJJSjzGGHZVbRP9UQ3lkmkmc0+XCHmj5WhwNNYjgbbmML7y0fsJT5RgvefAIFfHBg7fTY/i kBEimoUsTEQz+N4hbKwo1hULfVxDJStE4sbPhjbsPCrlXf6W9CxSyQ0qmZ2bXsLQYRj2xqd1 bpA+1o1j2N4/au1R/uSiUFjewJdT/LX1EklKDcQwpk06Af/N7VZtSfEJeRV04unbsKVXWZAk uAJyDDKN99ziC0Wz5kcPyVD1HNf8bgaqGDzrv3TfYjwqayRFcMf7xJaL9xXedMcAEQEAAcLB XwQYAQgACQUCUuE2fwIbDAAKCRBlw/kGpdefoG4XEACD1Qf/er8EA7g23HMxYWd3FXHThrVQ HgiGdk5Yh632vjOm9L4sd/GCEACVQKjsu98e8o3ysitFlznEns5EAAXEbITrgKWXDDUWGYxd pnjj2u+GkVdsOAGk0kxczX6s+VRBhpbBI2PWnOsRJgU2n10PZ3mZD4Xu9kU2IXYmuW+e5KCA vTArRUdCrAtIa1k01sPipPPw6dfxx2e5asy21YOytzxuWFfJTGnVxZZSCyLUO83sh6OZhJkk b9rxL9wPmpN/t2IPaEKoAc0FTQZS36wAMOXkBh24PQ9gaLJvfPKpNzGD8XWR5HHF0NLIJhgg 4ZlEXQ2fVp3XrtocHqhu4UZR4koCijgB8sB7Tb0GCpwK+C4UePdFLfhKyRdSXuvY3AHJd4CP 4JzW0Bzq/WXY3XMOzUTYApGQpnUpdOmuQSfpV9MQO+/jo7r6yPbxT7CwRS5dcQPzUiuHLK9i nvjREdh84qycnx0/6dDroYhp0DFv4udxuAvt1h4wGwTPRQZerSm4xaYegEFusyhbZrI0U9tJ B8WrhBLXDiYlyJT6zOV2yZFuW47VrLsjYnHwn27hmxTC/7tvG3euCklmkn9Sl9IAKFu29RSo d5bD8kMSCYsTqtTfT6W4A3qHGvIDta3ptLYpIAOD2sY3GYq2nf3Bbzx81wZK14JdDDHUX2Rs 6+ahAA== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 17/01/2025 10:43 pm, Stefano Stabellini wrote: > On Fri, 17 Jan 2025, Jan Beulich wrote: >> On 17.01.2025 13:24, Alejandro Vallejo wrote: >>> On Fri Jan 17, 2025 at 10:31 AM GMT, Roger Pau Monné wrote: >>>> On Thu, Jan 16, 2025 at 04:31:46PM -0800, Stefano Stabellini wrote: >>>>> On Wed, 1 Mar 2023, Jan Beulich wrote: >>>>>> While we want certain things turned off in shim-exclusive mode, doing >>>>>> so via "depends on !PV_SHIM_EXCLUSIVE" badly affects allyesconfig: Since >>>>>> that will turn on PV_SHIM_EXCLUSIVE, other options will be turned off as >>>>>> a result. Yet allyesconfig wants to enable as much of the functionality >>>>>> as possible. >>>>>> >>>>>> Retain PV_SHIM_EXCLUSIVE as a prompt-less option such that first of all >>>>>> C code using it can remain as is. This isn't just for less code churn, >>>>>> but also because I think that symbol is more logical to use in many >>>>>> (all?) places. >>>>>> >>>>>> Requested-by: Andrew Cooper >>>>>> Signed-off-by: Jan Beulich >>>>>> >>>>>> --- >>>>>> The new Kconfig control's name is up for improvement suggestions, but I >>>>>> think it's already better than the originally thought of >>>>>> FULL_HYPERVISOR. >>>>> I think the approach in general is OK, maybe we can improve the naming >>>>> further. What about one of the following? >>>>> >>>>> NO_PV_SHIM_EXCLUSIVE >>>>> PV_SHIM_NOT_EXCLUSIVE >>>> IMO negated options are confusing, and if possible I think we should >>>> avoid using them unless strictly necessary. >>> The problem is that the option is negative in nature. It's asking for >>> hypervisor without _something_. I do agree with Stefano that shim would be >>> better in the name. Otherwise readers are forced to play divination tricks. >>> >>> How about something like: >>> >>> SHIMLESS_HYPERVISOR >>> >>> That's arguably not negated, preserves "shim" in the name and has the correct >>> polarity for allyesconfig to yield the right thing. >> Except that a hypervisor with this option enabled isn't shim-less, but permits >> working in shim as well as in non-shim mode. > First, let's recognize that we have two opposing requirements. One > requirement is to make it as easy as possible to configure for the user. > Ideally without using negative CONFIG options, such as > NO_PV_SHIM_EXCLUSIVE. From the user point of view, honestly, > PV_SHIM_EXCLUSIVE is a pretty good name. Better than all of the others, > I think. > > On the other hand, we have the requirement that we don't want > allyesconfig to end up disabling a bunch of CONFIG options. Now this > requirement can be satisfied easily by adding something like > NO_PV_SHIM_EXCLUSIVE. However, it would go somewhat against the previous > requirement. > > So we need a compromise, something that doesn't end up disabling other > CONFIG options, to make allyesconfig happy, but also not too confusing > for the user (which is a matter of personal opinion). > > In short, expect that people will have different opinions on this and > will find different compromises better or worse. For one, I prefer to > compromise on "no negative CONFIG options" and use > PV_SHIM_NOT_EXCLUSIVE. Because it serves the allyesconfig goal, and > while it is not as clear as PV_SHIM_EXCLUSIVE, is still better than a > completely generic FULL_HYPERVISOR option, which means nothing to me. > > I cannot see a way to have a good and clear non-negated CONFIG option, > and also satisfy the allyesconfig requirement. So I prefer to compromise > on the "non-negated" part. Debating the naming is missing the point. The problem here is the wish to have PV_SHIM_EXCLUSIVE behave in a way that Kconfig is not capable of expressing.  Specifically, what is broken is having "lower level" options inhibit unrelated "higher level" options when the graph gets rescanned[1].  That's why we're in the laughable position of `make allyesconfig` turning off CONFIG_HVM. Jan, you want "echo PV_SHIM_EXCLUSIVE=y >> .config && make" to mean "reset me back to a PV Shim". Kconfig spells this "make $foo_defconfig" for an appropriately given foo. There should be: 1) an option called PV_SHIM_EXCLUSIVE which does *nothing* other than making the boolean be a compile time constant. 2) a pvshim_defconfig target which expresses what a pvshim ought to look like. Trying to fight against the behaviour of Kconfig is not a good use of anyone's time. ~Andrew [1] default to unrelated symbols is also broken for a related reason.  The result you get is sensitive to the order of processing of symbols.