From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6D9C423788; Wed, 22 Jul 2026 20:02:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784750579; cv=none; b=H1mcX5ZeFow3XPf3OLmhT+MifJZbqUbt+RiWbtclrZ/ALimAX1PpzJ0NwYCIMymZ7TgVaXqbN8JaI6JiUxOi8HkT4b0ErZtM5AWYJYVjWiOkuXJIoIqzd+FXXD1ZU7oXbtkKHFgmU9qE9yMgwE1a7NBYYdFY4hCFUHFyybhDxj4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784750579; c=relaxed/simple; bh=uqbBTPCzw4yRBeGp2Yr8m/BZSs55mdTxe1zylVnLMSU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=kJ4LGptt5aiU50SzMfrJMtaZxWGZ6gagNtCTuvr/FLMAIrm9S8qAO0Bdx4WUUJn5b+zjXHsQ7L3SzQ7OktKNLFFhdkdzQzxVx8LL5UKEsyqa2aixMUpujtuvpNUw4OEhk5k//L0lsqglTktmCI2g8czqNZvevv6b5ho0ZzS29l8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=Ifp9KV9R; arc=none smtp.client-ip=192.198.163.18 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="Ifp9KV9R" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1784750577; x=1816286577; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=uqbBTPCzw4yRBeGp2Yr8m/BZSs55mdTxe1zylVnLMSU=; b=Ifp9KV9RnPibkxsXzGv7y21HLNWv8lZC4PD8XCcGuD3pKeU8/+vEteUv zdD1moOSmz8vjMOOjKkrUfMyU4Iq07sMtppks/stjqoRXwgoiT2Xh7qOT F/HfdhZrDMTmXNQzKoVC1KloyZcrnweR2Bv0nGOzyExeF3FkOZTi45/oB S8my+urkkTj4Tg/4A60XeOIiagHjpA+qChEbLFerGXVt1uk7mqc7ySJ64 Jt4FgY6gqH3LPwjr7ULsAZjru69UUGu+y3Gj6zedUPiXdoJAbJULLpUwJ /i9ffgfVRUJtnmby1M8vOi7CGzn/LTGMoaXn2pBuY/Pq8TVrUnwl+1qWx g==; X-CSE-ConnectionGUID: ABLnf3UBRCSNQfdcZhNAWw== X-CSE-MsgGUID: 4FvI94aeRQGzxNT3Ga115g== X-IronPort-AV: E=McAfee;i="6800,10657,11854"; a="84523098" X-IronPort-AV: E=Sophos;i="6.25,179,1779174000"; d="scan'208";a="84523098" Received: from fmviesa010.fm.intel.com ([10.60.135.150]) by fmvoesa112.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2026 13:02:56 -0700 X-CSE-ConnectionGUID: n4bQqbtdSSSwOuzaoTMNAA== X-CSE-MsgGUID: WZ8ynCgBTUiBBT4oSyVU5Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,179,1779174000"; d="scan'208";a="254266571" Received: from sghuge-mobl2.amr.corp.intel.com (HELO [10.125.110.58]) ([10.125.110.58]) by fmviesa010-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 22 Jul 2026 13:02:53 -0700 Message-ID: <6f5060a7-0a64-49fc-81a3-ae88729ef794@intel.com> Date: Wed, 22 Jul 2026 13:02:53 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2 14/20] x86: mm: skip pud setup when using generic compile-time folded pagetable To: Yeoreum Yun Cc: Russell King , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Catalin Marinas , Will Deacon , Arnd Bergmann , Andrew Morton , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Michal Hocko , Lorenzo Stoakes , Tianrui Zhao , Bibo Mao , Anup Patel , Atish Patra , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonas Bonn , Stefan Kristiansson , Stafford Horne , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-openrisc@vger.kernel.org References: <20260722-dummy_ptxp3-v2-0-d9e4bad31e0a@arm.com> <20260722-dummy_ptxp3-v2-14-d9e4bad31e0a@arm.com> <0ea931f1-4801-4d32-b6ce-4787a8d3daa9@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; keydata= xsFNBE6HMP0BEADIMA3XYkQfF3dwHlj58Yjsc4E5y5G67cfbt8dvaUq2fx1lR0K9h1bOI6fC oAiUXvGAOxPDsB/P6UEOISPpLl5IuYsSwAeZGkdQ5g6m1xq7AlDJQZddhr/1DC/nMVa/2BoY 2UnKuZuSBu7lgOE193+7Uks3416N2hTkyKUSNkduyoZ9F5twiBhxPJwPtn/wnch6n5RsoXsb ygOEDxLEsSk/7eyFycjE+btUtAWZtx+HseyaGfqkZK0Z9bT1lsaHecmB203xShwCPT49Blxz VOab8668QpaEOdLGhtvrVYVK7x4skyT3nGWcgDCl5/Vp3TWA4K+IofwvXzX2ON/Mj7aQwf5W iC+3nWC7q0uxKwwsddJ0Nu+dpA/UORQWa1NiAftEoSpk5+nUUi0WE+5DRm0H+TXKBWMGNCFn c6+EKg5zQaa8KqymHcOrSXNPmzJuXvDQ8uj2J8XuzCZfK4uy1+YdIr0yyEMI7mdh4KX50LO1 pmowEqDh7dLShTOif/7UtQYrzYq9cPnjU2ZW4qd5Qz2joSGTG9eCXLz5PRe5SqHxv6ljk8mb ApNuY7bOXO/A7T2j5RwXIlcmssqIjBcxsRRoIbpCwWWGjkYjzYCjgsNFL6rt4OL11OUF37wL QcTl7fbCGv53KfKPdYD5hcbguLKi/aCccJK18ZwNjFhqr4MliQARAQABzUVEYXZpZCBDaHJp c3RvcGhlciBIYW5zZW4gKEludGVsIFdvcmsgQWRkcmVzcykgPGRhdmUuaGFuc2VuQGludGVs LmNvbT7CwXgEEwECACIFAlQ+9J0CGwMGCwkIBwMCBhUIAgkKCwQWAgMBAh4BAheAAAoJEGg1 lTBwyZKwLZUP/0dnbhDc229u2u6WtK1s1cSd9WsflGXGagkR6liJ4um3XCfYWDHvIdkHYC1t MNcVHFBwmQkawxsYvgO8kXT3SaFZe4ISfB4K4CL2qp4JO+nJdlFUbZI7cz/Td9z8nHjMcWYF IQuTsWOLs/LBMTs+ANumibtw6UkiGVD3dfHJAOPNApjVr+M0P/lVmTeP8w0uVcd2syiaU5jB aht9CYATn+ytFGWZnBEEQFnqcibIaOrmoBLu2b3fKJEd8Jp7NHDSIdrvrMjYynmc6sZKUqH2 I1qOevaa8jUg7wlLJAWGfIqnu85kkqrVOkbNbk4TPub7VOqA6qG5GCNEIv6ZY7HLYd/vAkVY E8Plzq/NwLAuOWxvGrOl7OPuwVeR4hBDfcrNb990MFPpjGgACzAZyjdmYoMu8j3/MAEW4P0z F5+EYJAOZ+z212y1pchNNauehORXgjrNKsZwxwKpPY9qb84E3O9KYpwfATsqOoQ6tTgr+1BR CCwP712H+E9U5HJ0iibN/CDZFVPL1bRerHziuwuQuvE0qWg0+0SChFe9oq0KAwEkVs6ZDMB2 P16MieEEQ6StQRlvy2YBv80L1TMl3T90Bo1UUn6ARXEpcbFE0/aORH/jEXcRteb+vuik5UGY 5TsyLYdPur3TXm7XDBdmmyQVJjnJKYK9AQxj95KlXLVO38lczsFNBFRjzmoBEACyAxbvUEhd GDGNg0JhDdezyTdN8C9BFsdxyTLnSH31NRiyp1QtuxvcqGZjb2trDVuCbIzRrgMZLVgo3upr MIOx1CXEgmn23Zhh0EpdVHM8IKx9Z7V0r+rrpRWFE8/wQZngKYVi49PGoZj50ZEifEJ5qn/H Nsp2+Y+bTUjDdgWMATg9DiFMyv8fvoqgNsNyrrZTnSgoLzdxr89FGHZCoSoAK8gfgFHuO54B lI8QOfPDG9WDPJ66HCodjTlBEr/Cwq6GruxS5i2Y33YVqxvFvDa1tUtl+iJ2SWKS9kCai2DR 3BwVONJEYSDQaven/EHMlY1q8Vln3lGPsS11vSUK3QcNJjmrgYxH5KsVsf6PNRj9mp8Z1kIG qjRx08+nnyStWC0gZH6NrYyS9rpqH3j+hA2WcI7De51L4Rv9pFwzp161mvtc6eC/GxaiUGuH BNAVP0PY0fqvIC68p3rLIAW3f97uv4ce2RSQ7LbsPsimOeCo/5vgS6YQsj83E+AipPr09Caj 0hloj+hFoqiticNpmsxdWKoOsV0PftcQvBCCYuhKbZV9s5hjt9qn8CE86A5g5KqDf83Fxqm/ vXKgHNFHE5zgXGZnrmaf6resQzbvJHO0Fb0CcIohzrpPaL3YepcLDoCCgElGMGQjdCcSQ+Ci FCRl0Bvyj1YZUql+ZkptgGjikQARAQABwsFfBBgBAgAJBQJUY85qAhsMAAoJEGg1lTBwyZKw l4IQAIKHs/9po4spZDFyfDjunimEhVHqlUt7ggR1Hsl/tkvTSze8pI1P6dGp2XW6AnH1iayn yRcoyT0ZJ+Zmm4xAH1zqKjWplzqdb/dO28qk0bPso8+1oPO8oDhLm1+tY+cOvufXkBTm+whm +AyNTjaCRt6aSMnA/QHVGSJ8grrTJCoACVNhnXg/R0g90g8iV8Q+IBZyDkG0tBThaDdw1B2l asInUTeb9EiVfL/Zjdg5VWiF9LL7iS+9hTeVdR09vThQ/DhVbCNxVk+DtyBHsjOKifrVsYep WpRGBIAu3bK8eXtyvrw1igWTNs2wazJ71+0z2jMzbclKAyRHKU9JdN6Hkkgr2nPb561yjcB8 sIq1pFXKyO+nKy6SZYxOvHxCcjk2fkw6UmPU6/j/nQlj2lfOAgNVKuDLothIxzi8pndB8Jju KktE5HJqUUMXePkAYIxEQ0mMc8Po7tuXdejgPMwgP7x65xtfEqI0RuzbUioFltsp1jUaRwQZ MTsCeQDdjpgHsj+P2ZDeEKCbma4m6Ez/YWs4+zDm1X8uZDkZcfQlD9NldbKDJEXLIjYWo1PH hYepSffIWPyvBMBTW2W5FRjJ4vLRrJSUoEfJuPQ3vW9Y73foyo/qFoURHO48AinGPZ7PC7TF vUaNOTjKedrqHkaOcqB185ahG2had0xnFsDPlx5y In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/22/26 10:18, Yeoreum Yun wrote: >>> @@ -1730,7 +1730,8 @@ static int populate_pud(struct cpa_data *cpa, unsigned long start, p4d_t *p4d, >>> /* >>> * Map everything starting from the Gb boundary, possibly with 1G pages >>> */ >>> - while (boot_cpu_has(X86_FEATURE_GBPAGES) && end - start >= PUD_SIZE) { >>> + while (CONFIG_PGTABLE_LEVELS > 3 && boot_cpu_has(X86_FEATURE_GBPAGES) && >>> + end - start >= PUD_SIZE) { >>> set_pud(pud, pud_mkhuge(pfn_pud(cpa->pfn, >>> canon_pgprot(pud_pgprot)))); >> This is an OK approach. But there's a way to fix this site *and* >> optimize a non-zero amount of other code at the same time. Add this hunk >> to arch/x86/Kconfig.cpufeatures: >> >> config X86_DISABLED_FEATURE_GBPAGES >> def_bool y >> depends on X86_32 >> >> That will turn the boot_cpu_has() check in to something that can be >> resolved at compile time. It has the added advantage of compiling out >> all of the code under X86_FEATURE_GBPAGES everywhere else in the tree. > Does it? when I glimpse check, this wouldn't be compiled since > there is no bit for X86_DISABLED_FEATURE_GBPAGES and defining the > DISABLED bit for FEATURE_GBPAGES seems odd since bit X86_FEATURE_GBPAGES > is already defined. x86 is a special snowflake here and all the similarly-named things glued together with magic makes them hard to grok. Our X86_FEATURE_* bits normally compile down to a bit in a bitmap in memory. But, there are also some optimizations in the helpers that access those bits. The optimizations turn bit checks like: if (bitmap[N] & bit) ... into a compile-time check: if (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0: (bitmap[N] & bit)) ... The DISABLED_MASK_BIT_SET() macro magic check if (for instance) X86_DISABLED_FEATURE_GBPAGES is around. Some processing of the Kconfig variables produces a header with X86_DISABLED_FEATURE_GBPAGES defined. > Instead of CONFIG_PGTABLE_LEVEL > 3, as above, would it be better to > add check IS_ENABLED(CONFIG_X86_DIRECT_GBPAGES)? That would definitely change the behavior. It honestly might be the _right_ change, but I'm ignoring that for the moment because even if it is best it is fodder for another patch, not this one. Please just keep the check against X86_FEATURE_GBPAGES for now.