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 C47DAC7EE31 for ; Thu, 26 Jun 2025 14:19:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3A94A6B009E; Thu, 26 Jun 2025 10:19:06 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 37F666B009F; Thu, 26 Jun 2025 10:19:06 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 26E006B00A0; Thu, 26 Jun 2025 10:19:06 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 146456B009E for ; Thu, 26 Jun 2025 10:19:06 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 6C10AB78C6 for ; Thu, 26 Jun 2025 14:19:05 +0000 (UTC) X-FDA: 83597758650.21.AAE17C9 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.9]) by imf28.hostedemail.com (Postfix) with ESMTP id 18562C0009 for ; Thu, 26 Jun 2025 14:19:02 +0000 (UTC) Authentication-Results: imf28.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=GkQ4C7Z2; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf28.hostedemail.com: domain of dave.hansen@intel.com designates 198.175.65.9 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1750947543; a=rsa-sha256; cv=none; b=Ux6ibjGmwRh54E7LMd9VfxpZq5n59elaRZdlD3P6zzFVxH96P4WZmbnfQ2hU9lNS/dLmCM JGd7UZiguk7pnaiQXDHU8vKoFzTH2JZmpQPB1LATQYqmR8x9jNW/a1AWgZoWkddMNVyoqE Ed+XXC143esc5VqKN/330xiPFqWkWbw= ARC-Authentication-Results: i=1; imf28.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=GkQ4C7Z2; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf28.hostedemail.com: domain of dave.hansen@intel.com designates 198.175.65.9 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1750947543; 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=Vb5QXm4VBPfveAmX6WIV8nmKODD4+cZvCZsfVHr+tOQ=; b=rJnCJLe0wJ91Czy2aSuLtV6jicBQDilEwEqE5Q2AhPwKScBrHNKOp88EDw9yYHQVgwEJ7v 9LpxQHEr7WQWkp8yxJl4NXjrxc5x39ZRWTUlcAslhDZFHXlEocu1AzOqWx6FyC6V1ej+bT vz+Oq8AQxeiFqsLGdaZX/AXP1XTLxSc= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1750947543; x=1782483543; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=mDnebU0I8mcl9/7kpWvfZue6oZRYGQwsMw+097cknuE=; b=GkQ4C7Z2bUpZiBtu1DXE6XJcbpy5tnQn1WOCttbm/MunaKEderIdKt6G f+UsWDvJqdBXvdD8kLcIYexahVL6BK75+esrKL4pSaHavTDcrH6cmlq7E b08SNQ8tCzDsdNBF0tCbvniFcCVA3/gjNr4jqZFFSvAxYgb6x3V6pDBkf 1jxi6P0X4/q3zzDU6DKUiID2CT68w5elKItGwigGKoUpLLadgkahvpi1A SKGfbFHiC+ru0dij23P4ZjlQ4ezK3d0WN4Cok72cfkN2LyJAVfbM8Y6kr O1JLxuJuupjNZkP1CKHKrBvqYMDggHGef86k/H65HytrxKE3k9uWbgobm g==; X-CSE-ConnectionGUID: 1GFpiihnStunmiRl/yzhkQ== X-CSE-MsgGUID: h+3Tb5laQ/aGeGcklToNvQ== X-IronPort-AV: E=McAfee;i="6800,10657,11475"; a="75792840" X-IronPort-AV: E=Sophos;i="6.16,267,1744095600"; d="scan'208";a="75792840" Received: from orviesa007.jf.intel.com ([10.64.159.147]) by orvoesa101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jun 2025 07:19:02 -0700 X-CSE-ConnectionGUID: GjVeWpZ+R9CX9zdwVpH6kw== X-CSE-MsgGUID: TE9kWg2MT4S+caMGEvN5CA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.16,267,1744095600"; d="scan'208";a="152693577" Received: from spandruv-desk1.amr.corp.intel.com (HELO [10.125.109.24]) ([10.125.109.24]) by orviesa007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jun 2025 07:19:01 -0700 Message-ID: <170dbb93-e9d9-4bd4-b56c-502841c21cd3@intel.com> Date: Thu, 26 Jun 2025 07:18:59 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv7 03/16] x86/alternatives: Disable LASS when patching kernel alternatives To: Peter Zijlstra , "Kirill A. Shutemov" Cc: Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , 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 References: <20250625125112.3943745-1-kirill.shutemov@linux.intel.com> <20250625125112.3943745-5-kirill.shutemov@linux.intel.com> <20250626134921.GK1613200@noisy.programming.kicks-ass.net> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: oifnm18xy8dn6cs3s8qkiurpdzspdwyz X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 18562C0009 X-HE-Tag: 1750947542-429442 X-HE-Meta: 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 O6CDUDsa Etk5c+N8JKohsVdDqi/NdD+nSe/SkYfiZI+fqAMwL1sYZtPgDEaXPKcMpqHUKT0pKQ0yqueTHo50sSkoBev4j/0zrq7Uzq053ciS2XViSvh9KUgowUV+osdetY+bIvw2XN+J7LbHvuiwqlkHtYpNNn7QqDR5PmtLn+CCvhSmXj87MnwcXUJ/NgvSKAlcALT9SQpfnDDguu59splZAd2CO6g7WH2t+zZE6eWHMfWWfEi+PIQkvxAbYFPDy9g== 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 6/26/25 06:49, Peter Zijlstra wrote: >> +static __always_inline void lass_enable_enforcement(void) >> +{ >> + alternative("", "clac", X86_FEATURE_LASS); >> +} >> + >> +static __always_inline void lass_disable_enforcement(void) >> +{ >> + alternative("", "stac", X86_FEATURE_LASS); >> +} > Much hate for this naming. WTH was wrong with lass_{clac,stac}()? > > We're not calling those other functions smap_{en,dis}able_enforcement() > either (and please don't take that as a suggestion, its terrible > naming). It was a response to a comment from Sohil about the delta between lass_{cl,st}ac() and plain {cl,st}ac() being subtle. They are subtle, but I don't think it's fixable with naming. There are lots of crazy gymnastics we could do. But there are so few sites where AC is twiddled for LASS that I don't think it's worth it. Let's just use the lass_{cl,st}ac() and comment both variants. First, the existing stac()/clac(): /* * Use these when accessing userspace (_PAGE_USER) * mappings, regardless of location. */ and the new ones: /* * Use these when accessing kernel mappings (!_PAGE_USER) * in the lower half of the address space. */ Any objections to doing that?