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X-CSE-ConnectionGUID: qOxqjhs8QDC5c6+IuUq9eA== X-CSE-MsgGUID: e19LEkQPQz2r7XC9hcD8/Q== X-IronPort-AV: E=McAfee;i="6700,10204,11348"; a="50859717" X-IronPort-AV: E=Sophos;i="6.13,296,1732608000"; d="scan'208";a="50859717" Received: from fmviesa001.fm.intel.com ([10.60.135.141]) by orvoesa103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2025 16:39:37 -0800 X-CSE-ConnectionGUID: StxpGDHDSbyAh5uQiajbzA== X-CSE-MsgGUID: FiydVNMLQ+SQcbnjn4HSPg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="145453200" Received: from mgoodin-mobl2.amr.corp.intel.com (HELO [10.125.109.220]) ([10.125.109.220]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Feb 2025 16:39:30 -0800 Message-ID: Date: Tue, 18 Feb 2025 16:39:34 -0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 29/30] x86/mm, mm/vmalloc: Defer flush_tlb_kernel_range() targeting NOHZ_FULL CPUs To: Valentin Schneider , Jann Horn Cc: linux-kernel@vger.kernel.org, x86@kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-riscv@lists.infradead.org, linux-perf-users@vger.kernel.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org, linux-hardening@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, bpf@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Juergen Gross , Ajay Kaher , Alexey Makhalov , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Peter Zijlstra , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , "Liang, Kan" , Boris Ostrovsky , Josh Poimboeuf , Pawan Gupta , Sean Christopherson , Paolo Bonzini , Andy Lutomirski , Arnd Bergmann , Frederic Weisbecker , "Paul E. McKenney" , Jason Baron , Steven Rostedt , Ard Biesheuvel , Neeraj Upadhyay , Joel Fernandes , Josh Triplett , Boqun Feng , Uladzislau Rezki , Mathieu Desnoyers , Lai Jiangshan , Zqiang , Juri Lelli , Clark Williams , Yair Podemsky , Tomas Glozar , Vincent Guittot , Dietmar Eggemann , Ben Segall , Mel Gorman , Kees Cook , Andrew Morton , Christoph Hellwig , Shuah Khan , Sami Tolvanen , Miguel Ojeda , Alice Ryhl , "Mike Rapoport (Microsoft)" , Samuel Holland , Rong Xu , Nicolas Saenz Julienne , Geert Uytterhoeven , Yosry Ahmed , "Kirill A. Shutemov" , "Masami Hiramatsu (Google)" , Jinghao Jia , Luis Chamberlain , Randy Dunlap , Tiezhu Yang References: <20250114175143.81438-1-vschneid@redhat.com> <20250114175143.81438-30-vschneid@redhat.com> <352317e3-c7dc-43b4-b4cb-9644489318d0@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 X-Rspam-User: X-Rspamd-Queue-Id: 54B2C40002 X-Stat-Signature: qynwqzq8yqckup1z81jri8pb18pfiiag X-Rspamd-Server: rspam03 X-HE-Tag: 1739925579-789935 X-HE-Meta: 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 /Tc6Ix+g DO2zb5JwUN8kdnGLj+nyFe4lPw2z2qovOdF7AyDdHx1nswaeoVIpG9Yroh36OLqLP335uK3qPoDr2aHKtThfiOih5VBGH+dSgFgnjEYcczGcyQQbreJUpCasaP/X+zx5Btzb7LS9nD5dGstwlCRNo4Qw3PmyH+r5bs6Rm5eY0XTa8/B74A0SxDySJVghjIUwa/x+QrmsNuIcnAl+vHpOmDCJsGVw4qqjTeFzVp0/BVWYbky/K0CczZd9AQ7lKcfrAT8Rx/KcXE/5UlXL5oCY8e7Tr1/lG+oAa3iinOmrCfp4eKqeNOnhU9uzTmZW5Y7fhIRQQ 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 2/18/25 14:40, Valentin Schneider wrote: >> In practice, it's mostly limited like that. >> >> Architecturally, there are no promises from the CPU. It is within its >> rights to cache anything from the page tables at any time. If it's in >> the CR3 tree, it's fair game. >> > So what if the VMEMMAP range *isn't* in the CR3 tree when a CPU is > executing in userspace? > > AIUI that's the case with kPTI - the remaining kernel pages should mostly > be .entry.text and cpu_entry_area, at least for x86. Having part of VMEMMAP not in the CR3 tree should be harmless while running userspace. VMEMMAP is a purely software structure; the hardware doesn't do implicit supervisor accesses to it. It's also not needed in super early entry. Maybe I missed part of the discussion though. Is VMEMMAP your only concern? I would have guessed that the more generic vmalloc() functionality would be harder to pin down.