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Peter Anvin" , "Kirill A. Shutemov" Cc: 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 , Sohil Mehta , 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, Yian Chen References: <20250620135325.3300848-1-kirill.shutemov@linux.intel.com> <20250620135325.3300848-2-kirill.shutemov@linux.intel.com> <73796800-819b-4433-b0ef-db852336d7a4@zytor.com> <0A71C898-B587-4292-AB05-6CA46BBD6F88@zytor.com> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 4A7C840008 X-Stat-Signature: m4gb8s8o5dkob8f3oti317o3sp55d7og X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1750741089-157939 X-HE-Meta: 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 RnFN4e+p MEXw90TLl7daEU9GhAMNsSP8OG5c0jG57kFplbVViMw1eWzBkpSqP5XbOaXLFytVlrkwrReEgI4otyFkG8wDdTkFdHBwwMFCOU80TM6w+t7ODy9Q8AYs2vL1CljrP2wLNZGCMLqbrW/ClPXuaDExHkhwO4DXwOi0wCG+zqHcKo5/gZoo6MdVc2qaKUxCuvZ+FhXX4WVZL0+iB5m8Ea+dlbBvTJ6tWhytNdhX15szz0PjODGzo7jYAi+FQhqOPmXQto0BArUJX/3BsVVH8xyeWi2wWIkSDW9O+Vlt7KaMSRszuKmZpdNU1xu0iPM7REasm56N+59smPoBp7raK7TMlXLgiNqlHhPiLv7g6fIXqFB3ZE/fx0tXduzAcliaY8EmZLu9sjpBTUTZ1aykw0iEnzQcJLj+UwfjWInZH0cM6AES7CRSzTL7Q0+v7W1TFQurzlFcK X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/23/2025 7:04 PM, H. Peter Anvin wrote: > On June 23, 2025 10:40:59 AM PDT, Xin Li wrote: >> On 6/20/2025 5:50 PM, H. Peter Anvin wrote: >>> On 2025-06-20 17:45, H. Peter Anvin wrote: >>>>> >>>>> But I simply hate adding a disabled feature that depends on !X86_64; >>>>> x86_64 has a broad scope, and new CPU features are often intentionally >>>>> not enabled for 32-bit. >>>>> >>>>> (X86_DISABLED_FEATURE_PCID is the only one before LASS) >>>> >>>> More importantly, it is wrong. >>>> >>>> The 32-bit build can depend on this feature not existing, therefore it SHOULD be listed as a disabled feature. >>>> >>> >>> Ok, that was word salad. What I meant was that the original patch is correct, and we SHOULD have this as a disabled feature. >> >> Agreed! >> >>> The reason is that it reduces the need to explicitly test for 32/64 bits for features that don't exist on 32 bits. When they are flagged as disabled, they get filtered out *at compile time*. >> >> It's better to make it depend on X86_32 directly rather than !X86_64: >> >> config X86_DISABLED_FEATURE_LASS >> def_bool y >> depends on X86_32 >> >> >> But the disabled feature list due to lack of 32-bit enabling will keep >> growing until we remove 32-bit kernel code. >> >> Wondering should we bother enforcing cpuid_deps[] on 32-bit? >> >> IOW, turn off the feature when its dependency isn’t satisfied on 32b-it; >> don’t just throw a warning and hope for the best. >> >> Thanks! >> Xin >> > > We should have the dependencies enforced; in fact, preferably we would enforce them at build time as well. > > Yeah, sounds something we can do later :)