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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> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; keydata= xsDNBGUPz1cBDACS/9yOJGojBFPxFt0OfTWuMl0uSgpwk37uRrFPTTLw4BaxhlFL0bjs6q+0 2OfG34R+a0ZCuj5c9vggUMoOLdDyA7yPVAJU0OX6lqpg6z/kyQg3t4jvajG6aCgwSDx5Kzg5 Rj3AXl8k2wb0jdqRB4RvaOPFiHNGgXCs5Pkux/qr0laeFIpzMKMootGa4kfURgPhRzUaM1vy bsMsL8vpJtGUmitrSqe5dVNBH00whLtPFM7IbzKURPUOkRRiusFAsw0a1ztCgoFczq6VfAVu raTye0L/VXwZd+aGi401V2tLsAHxxckRi9p3mc0jExPc60joK+aZPy6amwSCy5kAJ/AboYtY VmKIGKx1yx8POy6m+1lZ8C0q9b8eJ8kWPAR78PgT37FQWKYS1uAroG2wLdK7FiIEpPhCD+zH wlslo2ETbdKjrLIPNehQCOWrT32k8vFNEMLP5G/mmjfNj5sEf3IOKgMTMVl9AFjsINLHcxEQ 6T8nGbX/n3msP6A36FDfdSEAEQEAAc0WWGluIExpIDx4aW5Aenl0b3IuY29tPsLBDQQTAQgA NxYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89XBQkFo5qAAhsDBAsJCAcFFQgJCgsFFgID AQAACgkQa70OVx2uN1HUpgv/cM2fsFCQodLArMTX5nt9yqAWgA5t1srri6EgS8W3F+3Kitge tYTBKu6j5BXuXaX3vyfCm+zajDJN77JHuYnpcKKr13VcZi1Swv6Jx1u0II8DOmoDYLb1Q2ZW v83W55fOWJ2g72x/UjVJBQ0sVjAngazU3ckc0TeNQlkcpSVGa/qBIHLfZraWtdrNAQT4A1fa sWGuJrChBFhtKbYXbUCu9AoYmmbQnsx2EWoJy3h7OjtfFapJbPZql+no5AJ3Mk9eE5oWyLH+ QWqtOeJM7kKvn/dBudokFSNhDUw06e7EoVPSJyUIMbYtUO7g2+Atu44G/EPP0yV0J4lRO6EA wYRXff7+I1jIWEHpj5EFVYO6SmBg7zF2illHEW31JAPtdDLDHYcZDfS41caEKOQIPsdzQkaQ oW2hchcjcMPAfyhhRzUpVHLPxLCetP8vrVhTvnaZUo0xaVYb3+wjP+D5j/3+hwblu2agPsaE vgVbZ8Fx3TUxUPCAdr/p73DGg57oHjgezsDNBGUPz1gBDAD4Mg7hMFRQqlzotcNSxatlAQNL MadLfUTFz8wUUa21LPLrHBkUwm8RujehJrzcVbPYwPXIO0uyL/F///CogMNx7Iwo6by43KOy g89wVFhyy237EY76j1lVfLzcMYmjBoTH95fJC/lVb5Whxil6KjSN/R/y3jfG1dPXfwAuZ/4N cMoOslWkfZKJeEut5aZTRepKKF54T5r49H9F7OFLyxrC/uI9UDttWqMxcWyCkHh0v1Di8176 jjYRNTrGEfYfGxSp+3jYL3PoNceIMkqM9haXjjGl0W1B4BidK1LVYBNov0rTEzyr0a1riUrp Qk+6z/LHxCM9lFFXnqH7KWeToTOPQebD2B/Ah5CZlft41i8L6LOF/LCuDBuYlu/fI2nuCc8d m4wwtkou1Y/kIwbEsE/6RQwRXUZhzO6llfoN96Fczr/RwvPIK5SVMixqWq4QGFAyK0m/1ap4 bhIRrdCLVQcgU4glo17vqfEaRcTW5SgX+pGs4KIPPBE5J/ABD6pBnUUAEQEAAcLA/AQYAQgA JhYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89ZBQkFo5qAAhsMAAoJEGu9DlcdrjdR4C0L /RcjolEjoZW8VsyxWtXazQPnaRvzZ4vhmGOsCPr2BPtMlSwDzTlri8BBG1/3t/DNK4JLuwEj OAIE3fkkm+UG4Kjud6aNeraDI52DRVCSx6xff3bjmJsJJMb12mWglN6LjdF6K+PE+OTJUh2F dOhslN5C2kgl0dvUuevwMgQF3IljLmi/6APKYJHjkJpu1E6luZec/lRbetHuNFtbh3xgFIJx 2RpgVDP4xB3f8r0I+y6ua+p7fgOjDLyoFjubRGed0Be45JJQEn7A3CSb6Xu7NYobnxfkwAGZ Q81a2XtvNS7Aj6NWVoOQB5KbM4yosO5+Me1V1SkX2jlnn26JPEvbV3KRFcwV5RnDxm4OQTSk PYbAkjBbm+tuJ/Sm+5Yp5T/BnKz21FoCS8uvTiziHj2H7Cuekn6F8EYhegONm+RVg3vikOpn gao85i4HwQTK9/D1wgJIQkdwWXVMZ6q/OALaBp82vQ2U9sjTyFXgDjglgh00VRAHP7u1Rcu4 l75w1xInsg== In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 390EC4000D X-Stat-Signature: rruhhkeknefbf5abmgnzass4mmf5ggpf X-HE-Tag: 1750700521-786233 X-HE-Meta: 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 DckTlZ0U 7cPnaQ9lE7GvvV5NZx6M+52NQALvceYxxeqNRvEex1SR8RI/l/yyT2MLO3cOvVk4Ofjtg 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 6/20/2025 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