From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.9]) (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 32B0C211278; Tue, 14 Jan 2025 21:45:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.9 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736891150; cv=none; b=F9/L6rAV+2ckufy6R4gIgJi0hu5B7K6slAD2tOVDkoMLySo4wI957uArIZG7NnpyoIU682chs7N9ZQRiw6zlKfcnX8sk71qwqBkXawEMTyc5IQ8/SswfoUnh5lRglVXVstBLP0Q7TUeMWvY7FAxxh0YqqIQQMdBYsdXli0yxTIw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736891150; c=relaxed/simple; bh=FiKf+CBG14D8HJTJEsGFPQ/VuBsXxEyfgK3jkw1jBxs=; h=Content-Type:Message-ID:Date:MIME-Version:Subject:To:Cc: References:From:In-Reply-To; b=EUvA1TjAKf0TU1xjn9znuCrvNhzdHZsQK7Ztm/SFcxfLAsz/pj1pJzScUosE+e9Eh3BiO2qsgDUYBDgfuXbx5+wCXy0b+YjIT7VCSimcWvGBDi9e7O2rvHXprRytVf0aZV4uzZaGVEGThNlbw1UNUSrZUp/GjCmYoUAtpGgOf2c= 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=b+Kfwzxe; arc=none smtp.client-ip=192.198.163.9 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="b+Kfwzxe" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1736891149; x=1768427149; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to; bh=FiKf+CBG14D8HJTJEsGFPQ/VuBsXxEyfgK3jkw1jBxs=; b=b+KfwzxebR9+Gt9iPwQr+Khbqo9lR4xbY0IDwfygYQg7Yetcgw4OrpjW vFqYiErLxVt1c8U/0/CXvDOb8U0OzS8xPIeyDqkqBcCL1qKLxRAVc646Y zxcDCalZiNTNxwjnwsAmTaQJr9oDHSMveTklxmXZ6WUKzOfJkdzMIhZ+Z ScQvqvpsH3G5fLEtDGi7nz1LPScT/Oi92J7WPV1+1F6UkEinHj/xy0dVD j9dIBk+InEMY0JAjCgwFlEtohRQn630Rsd5Bd+lB2kiBo6iPlhnkvpKoh UtH8pli3RIcicAjGrRkSW5VJvQ9xglMzxPv+zMEmtYq3VzoPJdsVpet0C g==; X-CSE-ConnectionGUID: UTkdTLtaRja82ywPw+EImA== X-CSE-MsgGUID: vKd1oCuRQuaYNuT8bmbrKA== X-IronPort-AV: E=McAfee;i="6700,10204,11315"; a="47874048" X-IronPort-AV: E=Sophos;i="6.12,315,1728975600"; d="scan'208";a="47874048" Received: from orviesa007.jf.intel.com ([10.64.159.147]) by fmvoesa103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2025 13:45:47 -0800 X-CSE-ConnectionGUID: wClD8OzMQai+UBG5Nw361Q== X-CSE-MsgGUID: vzPbyt3kQ96Xavq3f7i4kA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.12,224,1728975600"; d="scan'208";a="105422933" Received: from ssimmeri-mobl2.amr.corp.intel.com (HELO [10.124.223.199]) ([10.124.223.199]) by orviesa007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jan 2025 13:45:42 -0800 Content-Type: multipart/mixed; boundary="------------n0n6ZXEhGiQA3ZVqsLB2u14D" Message-ID: <52311c3d-83cf-4dc4-bbcb-5fbca8eb249c@intel.com> Date: Tue, 14 Jan 2025 13:45:39 -0800 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 v4 26/30] x86,tlb: Make __flush_tlb_global() noinstr-compliant To: Valentin Schneider , 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 Cc: Peter Zijlstra , 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" , 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> <20250114175143.81438-27-vschneid@redhat.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: <20250114175143.81438-27-vschneid@redhat.com> This is a multi-part message in MIME format. --------------n0n6ZXEhGiQA3ZVqsLB2u14D Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/14/25 09:51, Valentin Schneider wrote: > + cr4 = this_cpu_read(cpu_tlbstate.cr4); > + asm volatile("mov %0,%%cr4": : "r" (cr4 ^ X86_CR4_PGE) : "memory"); > + asm volatile("mov %0,%%cr4": : "r" (cr4) : "memory"); > + /* > + * In lieu of not having the pinning crap, hard fail if CR4 doesn't > + * match the expected value. This ensures that anybody doing dodgy gets > + * the fallthrough check. > + */ > + BUG_ON(cr4 != this_cpu_read(cpu_tlbstate.cr4)); Let's say someone managed to write to cpu_tlbstate.cr4 where they cleared one of the pinned bits. Before this patch, CR4 pinning would WARN_ONCE() about it pretty quickly and also reset the cleared bits. After this patch, the first native_flush_tlb_global() can clear pinned bits, at least until native_write_cr4() gets called the next time. That seems like it'll undermine CR4 pinning at least somewhat. What keeps native_write_cr4() from being noinstr-compliant now? Is it just the WARN_ONCE()? If so, I'd kinda rather have a native_write_cr4_nowarn() that's noinstr-compliant but retains all the other CR4 pinning behavior. Would something like the attached patch be _worse_? --------------n0n6ZXEhGiQA3ZVqsLB2u14D Content-Type: text/x-patch; charset=UTF-8; name="cr4.patch" Content-Disposition: attachment; filename="cr4.patch" Content-Transfer-Encoding: base64 ZGlmZiAtLWdpdCBhL2FyY2gveDg2L2tlcm5lbC9jcHUvY29tbW9uLmMgYi9hcmNoL3g4Ni9r ZXJuZWwvY3B1L2NvbW1vbi5jCmluZGV4IDNlOTAzNzY5MDgxNC4uMjA0NGQ1MTZmMDZmIDEw MDY0NAotLS0gYS9hcmNoL3g4Ni9rZXJuZWwvY3B1L2NvbW1vbi5jCisrKyBiL2FyY2gveDg2 L2tlcm5lbC9jcHUvY29tbW9uLmMKQEAgLTQyMywyNCArNDIzLDQwIEBAIHZvaWQgbmF0aXZl X3dyaXRlX2NyMCh1bnNpZ25lZCBsb25nIHZhbCkKIH0KIEVYUE9SVF9TWU1CT0wobmF0aXZl X3dyaXRlX2NyMCk7CiAKLXZvaWQgX19ub19wcm9maWxlIG5hdGl2ZV93cml0ZV9jcjQodW5z aWduZWQgbG9uZyB2YWwpCit2b2lkIF9fbm9fcHJvZmlsZSBfX25hdGl2ZV93cml0ZV9jcjQo dW5zaWduZWQgbG9uZyB2YWwsIHVuc2lnbmVkIGxvbmcgKmJpdHNfY2hhbmdlZCkKIHsKLQl1 bnNpZ25lZCBsb25nIGJpdHNfY2hhbmdlZCA9IDA7Ci0KIHNldF9yZWdpc3RlcjoKIAlhc20g dm9sYXRpbGUoIm1vdiAlMCwlJWNyNCI6ICIrciIgKHZhbCkgOiA6ICJtZW1vcnkiKTsKIAog CWlmIChzdGF0aWNfYnJhbmNoX2xpa2VseSgmY3JfcGlubmluZykpIHsKIAkJaWYgKHVubGlr ZWx5KCh2YWwgJiBjcjRfcGlubmVkX21hc2spICE9IGNyNF9waW5uZWRfYml0cykpIHsKLQkJ CWJpdHNfY2hhbmdlZCA9ICh2YWwgJiBjcjRfcGlubmVkX21hc2spIF4gY3I0X3Bpbm5lZF9i aXRzOworCQkJKmJpdHNfY2hhbmdlZCA9ICh2YWwgJiBjcjRfcGlubmVkX21hc2spIF4gY3I0 X3Bpbm5lZF9iaXRzOwogCQkJdmFsID0gKHZhbCAmIH5jcjRfcGlubmVkX21hc2spIHwgY3I0 X3Bpbm5lZF9iaXRzOwogCQkJZ290byBzZXRfcmVnaXN0ZXI7CiAJCX0KLQkJLyogV2FybiBh ZnRlciB3ZSd2ZSBjb3JyZWN0ZWQgdGhlIGNoYW5nZWQgYml0cy4gKi8KLQkJV0FSTl9PTkNF KGJpdHNfY2hhbmdlZCwgInBpbm5lZCBDUjQgYml0cyBjaGFuZ2VkOiAweCVseCE/XG4iLAot CQkJICBiaXRzX2NoYW5nZWQpOwogCX0KIH0KKwordm9pZCBfX25vX3Byb2ZpbGUgbmF0aXZl X3dyaXRlX2NyNCh1bnNpZ25lZCBsb25nIHZhbCkKK3sKKwl1bnNpZ25lZCBsb25nIGJpdHNf Y2hhbmdlZCA9IDA7CisKKwlfX25hdGl2ZV93cml0ZV9jcjQodmFsLCAmYml0c19jaGFuZ2Vk KTsKKworCWlmICghYml0c19jaGFuZ2VkKQorCQlyZXR1cm4KKworCVdBUk5fT05DRShiaXRz X2NoYW5nZWQsICJwaW5uZWQgQ1I0IGJpdHMgY2hhbmdlZDogMHglbHghP1xuIiwKKwkJICBi aXRzX2NoYW5nZWQpOworfQorCit2b2lkIF9fbm9fcHJvZmlsZSBuYXRpdmVfd3JpdGVfY3I0 X25vd2Fybih1bnNpZ25lZCBsb25nIHZhbCkKK3sKKwl1bnNpZ25lZCBsb25nIGJpdHNfY2hh bmdlZCA9IDA7CisKKwlfX25hdGl2ZV93cml0ZV9jcjQodmFsLCAmYml0c19jaGFuZ2VkKTsK K30KKwogI2lmIElTX01PRFVMRShDT05GSUdfTEtEVE0pCiBFWFBPUlRfU1lNQk9MX0dQTChu YXRpdmVfd3JpdGVfY3I0KTsKICNlbmRpZgo= --------------n0n6ZXEhGiQA3ZVqsLB2u14D--