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 3CC2CE6F06C for ; Fri, 1 Nov 2024 16:07:28 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id ACCCC6B0095; Fri, 1 Nov 2024 12:07:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A56126B0096; Fri, 1 Nov 2024 12:07:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8CFAB6B0098; Fri, 1 Nov 2024 12:07:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 66CD66B0095 for ; Fri, 1 Nov 2024 12:07:27 -0400 (EDT) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 29A8BACB15 for ; Fri, 1 Nov 2024 16:07:27 +0000 (UTC) X-FDA: 82738005294.30.F903812 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.14]) by imf15.hostedemail.com (Postfix) with ESMTP id 467D1A0020 for ; Fri, 1 Nov 2024 16:06:55 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=i1oDbfCb; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf15.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.14 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1730477125; a=rsa-sha256; cv=none; b=DT+fpzYXu1HN5Yn8pIX4fpYHSYcku936VOvvhUmjdQti4Fkt9SpVuun0L6uZX+cD9p8XrO oKtaTjiecVHC6cCte6wPtnvDzSkfaTfDDWwqIsgabSCsGqRDvm3jSc8obNnKC/LsW0Tr15 CcmAxkI5+rafNmgxZiYmUIfE64iI/mA= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=i1oDbfCb; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf15.hostedemail.com: domain of dave.hansen@intel.com designates 192.198.163.14 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=1730477125; 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=cjh2R55wW/M353/ScD0KgEC/8/P4oT0XWbdyy90bq2I=; b=L+QLsD9+sxxdlUcwbpbr0578/bUZWmrHjluRtr0mOzOMxAYDNnlzB8TEi2UXgBEY1E/AMD 15+ZcgZDyZQT1Ib0o9QxKrIHMQJ+rLYWpXaY5VdxpRSKp902kTNvQZpSK2KQhUWlaMm9NJ Laxw5iZHhRCJM8M6EXWghLjFqNTFEHk= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1730477244; x=1762013244; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=RahQfZ/XUlkIuOR+dTOjhXIg4K5uTPhllesohsmYC0M=; b=i1oDbfCbh+ZkOonK0lZTkMtovxGPB8uEIqTuipVGytg9W0J0Pr+uzsGs S8kcIxfxpOSiWsXQ6FakqfgyCRYYy03OooSdluewHsRvxRB0AoPF0yy7U f0avpipp1DfYXBZWyORk4Z4VIg4PIipW6ElyZStY9rkHQQXIAemUGUHuM fKj1/xNmS8oWGR10poxvXassbBNf6sNf0yTI9Nn8jNSe9fwDvbK4Skuxn F1s6J5rrKlkRL7Iz6iBwfOuQlwh/hN6ag+DZcrxYjzBsH4UOkOgwbSrfb D+KGToKbFqz7ILPUKyh7Fwm3igg5WLsU1RTgy1M45YgVp8Kf+KSTCpOYN w==; X-CSE-ConnectionGUID: Pb+SWC7YSXSpqh9MNh0QSA== X-CSE-MsgGUID: FJtITwOeRg2+jx16cQ+tqA== X-IronPort-AV: E=McAfee;i="6700,10204,11243"; a="30459875" X-IronPort-AV: E=Sophos;i="6.11,250,1725346800"; d="scan'208";a="30459875" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa108.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Nov 2024 09:07:21 -0700 X-CSE-ConnectionGUID: 4dc8HIY5RT6JkqpGnUzUUg== X-CSE-MsgGUID: fkeBRFMzSu6jXbNStoM6pA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.11,250,1725346800"; d="scan'208";a="83107022" Received: from ccbilbre-mobl3.amr.corp.intel.com (HELO [10.124.220.146]) ([10.124.220.146]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Nov 2024 09:06:51 -0700 Message-ID: <784d1522-0451-4844-a334-8b7d49019437@intel.com> Date: Fri, 1 Nov 2024 09:06:50 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v3 0/6] Direct Map Removal for guest_memfd To: "Manwaring, Derek" , roypat@amazon.co.uk Cc: ackerleytng@google.com, agordeev@linux.ibm.com, aou@eecs.berkeley.edu, borntraeger@linux.ibm.com, bp@alien8.de, catalin.marinas@arm.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@redhat.com, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, graf@amazon.com, hca@linux.ibm.com, hpa@zytor.com, jgowans@amazon.com, jthoughton@google.com, kalyazin@amazon.com, kernel@xen0n.name, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-trace-kernel@vger.kernel.org, loongarch@lists.linux.dev, luto@kernel.org, mathieu.desnoyers@efficios.com, mhiramat@kernel.org, mingo@redhat.com, palmer@dabbelt.com, paul.walmsley@sifive.com, pbonzini@redhat.com, peterz@infradead.org, quic_eberman@quicinc.com, rostedt@goodmis.org, rppt@kernel.org, seanjc@google.com, shuah@kernel.org, svens@linux.ibm.com, tabba@google.com, tglx@linutronix.de, vannapurve@google.com, will@kernel.org, x86@kernel.org, xmarcalx@amazon.com References: <27646c08-f724-49f7-9f45-d03bad500219@amazon.co.uk> <2233397c-f423-40e3-8546-728b50ce0489@amazon.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: <2233397c-f423-40e3-8546-728b50ce0489@amazon.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 467D1A0020 X-Stat-Signature: 4zxwcx94qejqip7ruxthwkausur7bdbu X-Rspam-User: X-Rspamd-Server: rspam05 X-HE-Tag: 1730477215-496844 X-HE-Meta: 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 8/7dSMvj bu2PhxhgZfTWrr8C666dIKfLgQAmvSFv6i/P411PAJ/gVgvS5kIAuR4Ud8/xUSVougXXUKYJZPIEFjMWGoFWTO6QeWO11MqmBLLU8E9HyfO2SQwAyDAtAqptUfLa6uTWrT4t7a1BXO6gV/TjdqXGIpjS68mbWZJAxNWaruBamSZRJ/Q+8rHjup6IYiHabkKtUaReU9TwVALi8Zexc/kfElIozmsphb+ZfkTa1j1prBp01UwylsZWiHuxYU+QGnAAhYe2/K48YlzkyBbLcpAqbrgm/qA== 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 10/31/24 17:10, Manwaring, Derek wrote: > TDX and SEV encryption happens between the core and main memory, so > cached guest data we're most concerned about for transient execution > attacks isn't necessarily inaccessible. > > I'd be interested what Intel, AMD, and other folks think on this, but I > think direct map removal is worthwhile for CoCo cases as well. I'm not sure specifically which attacks you have in mind. Also, don't forget that TDX doesn't get any intra-system security from encryption itself. All that the encryption does is prevent some physical attacks. The main thing I think you want to keep in mind is mentioned in the "TDX Module v1.5 Base Architecture Specification"[1]: > Any software except guest TD or TDX module must not be able to > speculatively or non-speculatively access TD private memory, That's a pretty broad claim and it involves mitigations in hardware and the TDX module. I _think_ you might be thinking of attacks like MDS where some random microarchitectural buffer contains guest data after a VM exit and then an attacker extracts it. Direct map removal doesn't affect these buffers and doesn't mitigate an attacker getting the data out. TDX relies on other defenses. As for the CPU caches, direct map removal doesn't help or hurt anything. A malicious VMM would just map the guest data if it could and try to extract it if that were possible. If the attack is mitigated when the data is _mapped_, then it's certainly not possible _unmapped_. So why bother with direct map removal for TDX? A VMM write to TD private data causes machine checks. So any kernel bug that even accidentally writes to kernel memory can bring the whole system down. Not nice. 1. https://cdrdv2.intel.com/v1/dl/getContent/733575