From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id E3F69C7115C for ; Sat, 21 Jun 2025 00:51:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 624D56B008C; Fri, 20 Jun 2025 20:51:07 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6070B6B0093; Fri, 20 Jun 2025 20:51:07 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 539EB6B0095; Fri, 20 Jun 2025 20:51:07 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 3EE736B008C for ; Fri, 20 Jun 2025 20:51:07 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id AD394817B1 for ; Sat, 21 Jun 2025 00:51:06 +0000 (UTC) X-FDA: 83577578532.21.E0A14A0 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) by imf05.hostedemail.com (Postfix) with ESMTP id 990F4100009 for ; Sat, 21 Jun 2025 00:51:04 +0000 (UTC) Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=zytor.com header.s=2025052101 header.b=VUIymHWY; spf=pass (imf05.hostedemail.com: domain of hpa@zytor.com designates 198.137.202.136 as permitted sender) smtp.mailfrom=hpa@zytor.com; dmarc=pass (policy=none) header.from=zytor.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1750467065; a=rsa-sha256; cv=none; b=0O2UUj7HpSbUhmlUWix3bO7dgg1COK4q5RCjY76Aylbo1SGbNp7wvmzOMi0ckZ8OJLVn8u LDwaDFTu3Aa0y019AVuH3Ou1HKxUO+ytQCOE0I5k/2rZGPNCOJFtPqTHJY77NMkscbrx79 4DfpPiooKvM5hDPBB9TZe4CN55bVh4g= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=zytor.com header.s=2025052101 header.b=VUIymHWY; spf=pass (imf05.hostedemail.com: domain of hpa@zytor.com designates 198.137.202.136 as permitted sender) smtp.mailfrom=hpa@zytor.com; dmarc=pass (policy=none) header.from=zytor.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1750467065; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=8mp4H2Dh4pCq+5wlyN9ZrtiHLJlnNsb33zOx+M9tfYo=; b=P8ACBAq2yrhM/uJiZqejMNNnqDPjWpm6qTenf5qc6/A3AE1w/O75sMVUeylcZLJVF2w2Rm y8gvClOncEiv1bxxEL0EA3zTIlMRCBSLdkikcDCj9A/Mmuy+kazQfcJLllDL0RGSbLS1Ta P7bN59axgfi0VuHZi0UxHji5jmr+Iy4= Received: from [172.27.2.41] (c-76-133-66-138.hsd1.ca.comcast.net [76.133.66.138]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 55L0oJpw005744 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 20 Jun 2025 17:50:19 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 55L0oJpw005744 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025052101; t=1750467022; bh=8mp4H2Dh4pCq+5wlyN9ZrtiHLJlnNsb33zOx+M9tfYo=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=VUIymHWYeg2zZU8ZTGE3x5uN5qQUav/L2hRU+ARb5VILrC1d2nyCWg38sm9PrcVDv DZ+vl6tFy8/5wuWp/gjs+vImUdfo4F/ohy8Oe2dkKSj3wa41PPW+d9PizYJXnVo23E bD6npqiarkKjTl+oukVEzViu/IgPtYs7w22RTch3mnxmfQsdVppzJgBJ1x3uRbaATa Z9v/1UEif3rlIOJJ8ljoo/Q10T+YK2aWBRcxfyZGW4S0TgMJG9sIpYJyN+T4qyRfMA SqGeVbbXhKQpOOSU4cST9tzdxKY6XmfWR7yOkw9ZVKBxxursV3ek3k3ve30+jA8Tck dYRAvXaQg3t8g== Message-ID: Date: Fri, 20 Jun 2025 17:50:19 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv6 01/16] x86/cpu: Enumerate the LASS feature bits From: "H. 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 References: <20250620135325.3300848-1-kirill.shutemov@linux.intel.com> <20250620135325.3300848-2-kirill.shutemov@linux.intel.com> Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 990F4100009 X-Stat-Signature: 6cuxbdjrwu8wckg88gb3heuiopygfqy6 X-Rspam-User: X-HE-Tag: 1750467064-178852 X-HE-Meta: U2FsdGVkX1/aSfq32HyvS8az2mV6i5cnnz9M2lUzAd+K22jlrHSKAMEBrrBekoCPva2R9Jj9nbeg290z7JY3FK3QNHGRAWkbn41WMH3lo0A4Iw5Jv3wMsgRa5s7ND0rJBqOQO+Iw5BVgeSgRfCsmCAELUpaMp0r1//tqvhTexDk8fYDLODcNWXY2ADe1JBsgcvq79P+7UsxO1gJOwPWkTkjlpgo+QS1MHqTcBs7XaQOcRM7Ojii9tmNlIyeZaT7cV0qjJRDodStHTlApVltX/raxWgKm+EiK9xPKlFmwIDG+8EPzm7JbXqMN4zK+u1mHb7TDzY/j7eJ/qs+n+TJbogVXdZNKQRkTriBnDiPur8ZwgfsLISuj/sPhg50+beD00jb3+etYqeoMIQQvT2zbSCQkCUzaxt924MP7DzkF4h2SQdgaTrGxan2QIbH2cPPk4loolzzRvlcMmLpqym7nG+h2UuIJVZxlHGC53jwyd5b6oVf5NbDHWe9YEwEKayUjR2jvIqcmHfhONOOmRgYs1W1oSv7z6C0fWGapNR35xN8DN5YnlEv+CSZ3rdo/1iDlh9YnQskKXYoqJATYVHoZScg0ZJ5aaIfIoI+tTgUWuEGBllzlm2BjvYtlPuRvgKngBwyUzIWPnQ6073baG1VRG2a9bUAn79GWhCo9V3LaRzivlU6avSequOsQFtCLUtF/rlHVVwbUzl5JpA4WT2uPQi39vTxpPUdkA6PWU4XTynaL1WzhCyLmiw6PDPIa1bRs1Ry5UoJUqdCBoJypFXj9+6wl8IyLAzJTUTrFvd2A2oGq+ghpF3BdexrP0dZYEmWAzLFvho4rw8qAs8fNIhQORvMaCfNyU5h2HLCWkdWqEJrAW02qQcucGWoZT4g0tCftb4rhg2FMG0Vm1bdb5ZEWJxR8nybsFuz1TiaWHpNKwBpnpkT8eGF6FyuQt38GCwGKjcO9341Uq1k02ZoAp4T xDaQUOoD 5yrnVP4SIXtVR+4LjF+gTwAzGfROkf8Ie/iwCqdFBDXgmdO+++EeqxRHBkvJLBdGvVf3SXoafS+DIsES+GUIPRgB/vFfA4Fcow17jKJnN5OU7NyYdGBIwwv+yg136TAtf834xm1W5QV03HdIAxhPIelDDZefCAHPxpDoVrZc85OIXiYYAumtJYsxysxmjYN7NYxL0/Tmp5OOyqyl69jkVQh89IqNTiDCzfDAnNfBd+HtnujCXUG1/AZWO17vP3OPVz4fiTmsocpKbCV+PEVAtjAs3V3QNJ82r4wEZLkq90ty//JdRvbl7TsNAnh6IMohDBJPaSbf9JtMtOnQqQkP7KETW5nlvkrz7Sb6yYl+p5s2ywvo= 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 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