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Peter Anvin" To: Xin Li , "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 Subject: Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits User-Agent: K-9 Mail for Android In-Reply-To: References: <20250620135325.3300848-1-kirill.shutemov@linux.intel.com> <20250620135325.3300848-2-kirill.shutemov@linux.intel.com> Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: B72F140006 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 53jzcwm4z8kugrdykk1nqmy93a9jtewu X-HE-Tag: 1750466804-604033 X-HE-Meta: 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 cldE1DS7 QVze8MezPDkjsH/zAuZjYFR3ztwOMKRqzG56R9+A0psOf6K6NsMOgy+XvNNMe0oUTFjnaipW4uuPr4qsOg2n1m3nl6zXycON87/aUZcjsnpzI6Qn9CohOeUZRYx8KbQBMvc6RuUxBswEiuamKNTRGPIOpUPjCd04Uy4CAb3orbp0Ehmgft8UN4dgPbXrD2fPV6mgC0VIcd6tZNAmN4rYKfplXv55c4/ZcmprDe5JPKW+cm/15lQkzvnPjTrg0wU0/k0eGThyde1CjWrT/DsAjzijWnS0S8CTToEk7qczXxZgm3caDwn1Q7RcwfNTPUGkbzbN+w8xj/pUF2MYRjx4HZYkdI7M8WCro6Jy2vi2V2ul5iPy9RuPxU5+8CVDWgpRhOV96b7eZvh0YWqHfWsXHoUpvcBhBX50CRizzV24lCeXo5ts= 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 June 20, 2025 4:46:21 PM PDT, Xin Li wrote: >On 6/20/2025 10:31 AM, Kirill A=2E Shutemov wrote: >> On Fri, Jun 20, 2025 at 08:36:30AM -0700, Xin Li wrote: >>> On 6/20/2025 6:53 AM, Kirill A=2E Shutemov wrote: >>>> diff --git a/arch/x86/Kconfig=2Ecpufeatures b/arch/x86/Kconfig=2Ecpuf= eatures >>>> index 250c10627ab3=2E=2E9574c198fc08 100644 >>>> --- a/arch/x86/Kconfig=2Ecpufeatures >>>> +++ b/arch/x86/Kconfig=2Ecpufeatures >>>> @@ -124,6 +124,10 @@ config X86_DISABLED_FEATURE_PCID >>>> def_bool y >>>> depends on !X86_64 >>>> +config X86_DISABLED_FEATURE_LASS >>>> + def_bool y >>>> + depends on !X86_64 >>>> + >>>> config X86_DISABLED_FEATURE_PKU >>>> def_bool y >>>> depends on !X86_INTEL_MEMORY_PROTECTION_KEYS >>>=20 >>> You don't need to add X86_DISABLED_FEATURE_LASS, because the LASS code >>> is NOT optional at build time, i=2Ee=2E, you now don't have CONFIG_X86= _LASS=2E >>=20 >> Hmm=2E But it is optional=2E It depends on CONFIG_X86_64=2E I don't thi= nk we >> want it to be advertised on 32-bit kernels=2E >>=20 > >I kind of ignore 32-bit=2E=2E=2E > >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=2E > >(X86_DISABLED_FEATURE_PCID is the only one before LASS) > > More importantly, it is wrong=2E=20 The 32-bit build can depend on this feature not existing, therefore it SHO= ULD be listed as a disabled feature=2E