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Thu, 29 Feb 2024 04:05:42 -0800 (PST) Message-ID: Date: Thu, 29 Feb 2024 12:05:38 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 23/23] xen/README: add compiler and binutils versions for RISC-V64 Content-Language: en-GB To: Julien Grall , Jan Beulich Cc: George Dunlap , Stefano Stabellini , Wei Liu , xen-devel@lists.xenproject.org, Oleksii Kurochko References: <73a38d85-0798-4cfa-8625-0f8c9e05b2a3@suse.com> <80fb8091-9a26-40a4-b2e7-371df9411861@xen.org> <889b132b-b92e-465b-94af-4e4133e4c297@suse.com> <52188e88-374c-449f-a71c-bfce9b6d07f4@xen.org> 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: <52188e88-374c-449f-a71c-bfce9b6d07f4@xen.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 29/02/2024 10:23 am, Julien Grall wrote: >>>> IOW it is hard for me to see why RISC-V needs stronger restrictions >>>> here >>>> than other architectures. It ought to be possible to determine a >>>> baseline >>>> version. Even if taking the desire to have "pause" available as a >>>> requirement, gas (and presumably gld) 2.36.1 would already suffice. >>> >>> I think we want to bump it on Arm. There are zero reasons to try to >>> keep >>> a lower versions if nobody tests/use it in production. >>> >>> I would suggest to do the same on x86. What's the point of try to >>> support Xen with a 15+ years old compiler? >> >> It could have long been bumped if only a proper scheme to follow for >> this and future bumping would have been put forward by anyone keen on >> such bumping, like - see his reply - e.g. Andrew. You may recall that >> this was discussed more than once on meetings, with no real outcome. >> I'm personally not meaning to stand in the way of such bumping as long >> as it's done in a predictable manner, but I'm not keen on doing so and >> hence I don't view it as my obligation to try to invent a reasonable >> scheme. (My personal view is that basic functionality should be >> possible to have virtually everywhere, whereas for advanced stuff it >> is fine to require a more modern tool chain.) > > That's one way to see it. The problem with this statement is a user > today is mislead to think you can build Xen with any GCC versions > since 4.1. I don't believe we can guarantee that and we are exposing > our users to unnecessary risk. > > In addition to that, I agree with Andrew. This is preventing us to > improve our code base and we have to carry hacks for older compilers. I don't think anyone here is suggesting that we switch to a bleeding-edge-only policy.  But 15y of support is extreme in the opposite direction. Xen ought to be buildable in the contemporary distros of the day, and I don't think anyone is going to credibly argue otherwise. But, it's also fine for new things to have newer requirements. Take CET for example.  I know we have disagreements on exactly how it's toolchain-conditionalness is implemented, but the basic principle of "If you want shiny new optional feature $X, you need newer toolchain $Y" is entirely fine. A brand new architecture is exactly the same.  Saying "this is the minimum, because it's what we test" doesn't preclude someone coming along and saying "can we use $N-1 ?  See here it works, and here's a change to CI test it". Anyway, its clear we need to write some policy on this, before making specific adjustments.  To get started, is there going to be any objection whatsoever on some principles which begin as follows: * For established architectures, we expect Xen to be buildable on the common contemporary distros.  (i.e. minima is not newer than what's available in contemporary distros, without a good reason) * Optional features explicitly may have newer minima, generally chosen by when toolchain support landed and/or was bugfixed suitably to be usable. * Xen won't expect to update minima "just because".  But updates across-the-board will be considered periodically where it doesn't conflict with point 1, and where changing the minima allows us to use a new feature to have a positive impact on the codebase. * We always reserve the right to update minima to e.g. avoid crippling code generation bugs, even if it conflicts with point 1.  Where workarounds can reasonably be done, they ought to be preferred, but this is ultimately at the discretion of the relevant architecture maintainers. ? ~Andrew