From: "H. Peter Anvin" <hpa@zytor.com>
To: Xin Li <xin@zytor.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Ard Biesheuvel <ardb@kernel.org>,
"Paul E. McKenney" <paulmck@kernel.org>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Xiongwei Song <xiongwei.song@windriver.com>,
Xin Li <xin3.li@intel.com>,
"Mike Rapoport (IBM)" <rppt@kernel.org>,
Brijesh Singh <brijesh.singh@amd.com>,
Michael Roth <michael.roth@amd.com>,
Tony Luck <tony.luck@intel.com>,
Alexey Kardashevskiy <aik@amd.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jonathan Corbet <corbet@lwn.net>,
Sohil Mehta <sohil.mehta@intel.com>,
Ingo Molnar <mingo@kernel.org>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Kai Huang <kai.huang@intel.com>,
Sandipan Das <sandipan.das@amd.com>,
Breno Leitao <leitao@debian.org>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Alexei Starovoitov <ast@kernel.org>, Hou Tao <houtao1@huawei.com>,
Juergen Gross <jgross@suse.com>,
Vegard Nossum <vegard.nossum@oracle.com>,
Kees Cook <kees@kernel.org>, Eric Biggers <ebiggers@google.com>,
Jason Gunthorpe <jgg@ziepe.ca>,
"Masami Hiramatsu (Google)" <mhiramat@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Luis Chamberlain <mcgrof@kernel.org>,
Yuntao Wang <ytcoode@gmail.com>,
Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Tejun Heo <tj@kernel.org>, Changbin Du <changbin.du@huawei.com>,
Huang Shijie <shijie@os.amperecomputing.com>,
Geert Uytterhoeven <geert+renesas@glider.be>,
Namhyung Kim <namhyung@kernel.org>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-efi@vger.kernel.org, linux-mm@kvack.org,
Yian Chen <yian.chen@intel.com>
Subject: Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits
Date: Fri, 20 Jun 2025 17:50:19 -0700 [thread overview]
Message-ID: <f04936b7-e1e1-4a63-a907-33315af0dd8f@zytor.com> (raw)
In-Reply-To: <D8783A84-119A-4981-9EB1-12C21BB34714@zytor.com>
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.
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*.
-hpa
next prev parent reply other threads:[~2025-06-21 0:51 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-20 13:53 [PATCHv6 00/16] x86: Enable Linear Address Space Separation support Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits Kirill A. Shutemov
2025-06-20 15:25 ` Dave Hansen
2025-06-20 15:36 ` Xin Li
2025-06-20 17:31 ` Kirill A. Shutemov
2025-06-20 23:46 ` Xin Li
2025-06-21 0:45 ` H. Peter Anvin
2025-06-21 0:50 ` H. Peter Anvin [this message]
2025-06-23 17:40 ` Xin Li
2025-06-24 2:04 ` H. Peter Anvin
2025-06-24 4:57 ` Xin Li
2025-06-24 5:11 ` Xin Li
2025-06-20 16:02 ` Randy Dunlap
2025-06-20 16:12 ` Xin Li
2025-06-20 16:16 ` Randy Dunlap
2025-06-20 16:35 ` Borislav Petkov
2025-06-20 17:33 ` Kirill A. Shutemov
2025-06-20 18:29 ` Borislav Petkov
2025-06-23 8:17 ` Kirill A. Shutemov
2025-06-23 10:21 ` Borislav Petkov
2025-06-23 13:42 ` Kirill A. Shutemov
2025-06-26 15:18 ` Borislav Petkov
2025-06-26 16:07 ` Borislav Petkov
2025-06-26 17:21 ` Dave Hansen
2025-06-27 10:25 ` Kirill A. Shutemov
2025-06-27 10:43 ` Borislav Petkov
2025-06-27 13:57 ` Dave Hansen
2025-06-20 18:14 ` Sohil Mehta
2025-06-20 18:24 ` Dave Hansen
2025-06-20 23:10 ` Sohil Mehta
2025-06-23 16:25 ` Luck, Tony
2025-06-23 16:42 ` Dave Hansen
2025-06-23 23:13 ` Luck, Tony
2025-06-23 23:36 ` H. Peter Anvin
2025-06-24 0:10 ` Luck, Tony
2025-06-24 2:03 ` H. Peter Anvin
2025-06-25 18:51 ` H. Peter Anvin
2025-06-20 13:53 ` [PATCHv6 02/16] x86/asm: Introduce inline memcpy and memset Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 03/16] x86/alternatives: Disable LASS when patching kernel alternatives Kirill A. Shutemov
2025-06-20 15:33 ` Dave Hansen
2025-06-20 17:18 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 04/16] x86/efi: Move runtime service initialization to arch/x86 Kirill A. Shutemov
2025-06-20 15:35 ` Dave Hansen
2025-06-20 17:42 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 05/16] x86/cpu: Defer CR pinning setup until after EFI initialization Kirill A. Shutemov
2025-06-20 15:44 ` Dave Hansen
2025-06-20 13:53 ` [PATCHv6 06/16] efi: Disable LASS around set_virtual_address_map() EFI call Kirill A. Shutemov
2025-06-20 15:55 ` Dave Hansen
2025-06-20 17:50 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 07/16] x86/vsyscall: Reorganize the #PF emulation code Kirill A. Shutemov
2025-06-20 18:43 ` Dave Hansen
2025-06-20 23:08 ` Andrew Cooper
2025-06-20 23:18 ` Sohil Mehta
2025-06-20 23:29 ` Andrew Cooper
2025-06-20 23:21 ` Dave Hansen
2025-06-21 3:35 ` H. Peter Anvin
2025-06-23 12:41 ` Kirill A. Shutemov
2025-06-23 12:46 ` Andrew Cooper
2025-06-23 15:32 ` Dave Hansen
2025-06-23 15:45 ` Andrew Cooper
2025-06-24 11:37 ` Kirill A. Shutemov
2025-06-24 14:11 ` Dave Hansen
2025-06-24 14:59 ` [PATCH] x86/vsyscall: Do not require X86_PF_INSTR to emulate vsyscall Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 08/16] x86/traps: Consolidate user fixups in exc_general_protection() Kirill A. Shutemov
2025-06-20 14:47 ` Dave Hansen
2025-06-20 13:53 ` [PATCHv6 09/16] x86/vsyscall: Add vsyscall emulation for #GP Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 10/16] x86/vsyscall: Disable LASS if vsyscall mode is set to EMULATE Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 11/16] x86/cpu: Set LASS CR4 bit as pinning sensitive Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 12/16] x86/traps: Communicate a LASS violation in #GP message Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 13/16] x86/traps: Handle LASS thrown #SS Kirill A. Shutemov
2025-06-20 15:20 ` Xin Li
2025-06-20 17:53 ` Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 14/16] x86/cpu: Make LAM depend on LASS Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 15/16] x86/cpu: Enable LASS during CPU initialization Kirill A. Shutemov
2025-06-20 13:53 ` [PATCHv6 16/16] x86: Re-enable Linear Address Masking Kirill A. Shutemov
2025-06-20 15:38 ` [PATCHv6 00/16] x86: Enable Linear Address Space Separation support Dave Hansen
2025-06-20 22:04 ` Andrew Cooper
2025-06-20 22:29 ` H. Peter Anvin
2025-06-20 22:43 ` H. Peter Anvin
2025-06-20 22:46 ` Dave Hansen
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