From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.19]) (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 B9B481BE871 for ; Thu, 1 May 2025 20:18:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.19 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746130690; cv=none; b=Tz/0pi4i3KTqjx2vhj6qkdhLAmwIlySJLb8KYcCdA6gAUTLKYwGBHjOUOkuZBmgH6T+dzuX+FZ5M66HiHWMMct3gUWBZ/sqkk4VVVOIgEUDLDQvL4s0X/66Mpf+dK7QG8ThpB7O3d84jdFaCnfBHc9pT7WsRB12AcaauBemzlzg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746130690; c=relaxed/simple; bh=R2/jMdX8R/EJUf2Ulk6iVXzRVMgQF+fdX0Mg7kaFx8I=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GpIkEpRAJmzIfvYGYSXkm+NYa1auYJttMC7rRev2/JuCr2aczdIiT4HldwkKIUxprqV7crk1Mj2mQI/XKLbrmRUrfArpY35gA6X5gQMvwPdsJTeEi1urzUBHVEiHiJz8scwS5jWB1z7uS8Nu5n6fsidfEf3ld6n5XOJLh9tHTI4= 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=VIO5HqxN; arc=none smtp.client-ip=198.175.65.19 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="VIO5HqxN" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1746130689; x=1777666689; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=R2/jMdX8R/EJUf2Ulk6iVXzRVMgQF+fdX0Mg7kaFx8I=; b=VIO5HqxNB8VjofSLf4NwBlFKTGulZg81ZRtK+ROVniwTiMWdGV1Dj96K FCMMbyl1lPcUbeLFAHUXRPpYOoKxWaKgtfRqUF52ie1ZUrijdWPcJyNTk +ZZJNSwkJOXXokikFbYfASsaALTIqHT+NEXruTpITtago0/sP1mmFZcku jDiOy1UZ5YToNJKfuYemzKtondAx44EC1wzQ4ItpG4hoiBKuTn6vvpd5s Pp2vDJpS4v6nlvrzySY/jNz9hUguh/fkYm7CSOwsxgkL6EEYaB9VFIkIc 9B6klQAAoo8q72I2hts4FwfDVLgkxrXDsYzU/4ttawRds1qXy8q763Xoh g==; X-CSE-ConnectionGUID: XC5SdOutR76JnYYLQsUtAA== X-CSE-MsgGUID: SV3KuPlxQY+EdA3zZ6mF5Q== X-IronPort-AV: E=McAfee;i="6700,10204,11420"; a="47696141" X-IronPort-AV: E=Sophos;i="6.15,254,1739865600"; d="scan'208";a="47696141" Received: from orviesa005.jf.intel.com ([10.64.159.145]) by orvoesa111.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 May 2025 13:18:08 -0700 X-CSE-ConnectionGUID: 4W9HaQvrQeONBkHNsUjd4Q== X-CSE-MsgGUID: HrTUecZ4RySYJmPPznnnFQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.15,254,1739865600"; d="scan'208";a="139648922" Received: from rfrazer-mobl3.amr.corp.intel.com (HELO [10.124.220.24]) ([10.124.220.24]) by orviesa005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 May 2025 13:18:07 -0700 Message-ID: <61b4cbf2-efdb-4023-9e2a-1185ee308d6e@intel.com> Date: Thu, 1 May 2025 13:18:04 -0700 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5] x86/devmem: Drop /dev/mem access for confidential guests To: Arnd Bergmann , Dan Williams , Dave Hansen Cc: Greg Kroah-Hartman , Ingo Molnar , Kees Cook , "Kirill A. Shutemov" , Michael Ellerman , Naveen N Rao , Nikolay Borisov , stable@vger.kernel.org, Suzuki K Poulose , Vishal Annapurve , x86@kernel.org, linux-coco@lists.linux.dev References: <20250430024622.1134277-1-dan.j.williams@intel.com> <20250430024622.1134277-3-dan.j.williams@intel.com> <0bdb1876-0cb3-4632-910b-2dc191902e3e@app.fastmail.com> <6812c6cda0575_1d6a294d7@dwillia2-xfh.jf.intel.com.notmuch> <5f80ae16-8d41-4a68-b978-c1bb60fce3f1@app.fastmail.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: <5f80ae16-8d41-4a68-b978-c1bb60fce3f1@app.fastmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/1/25 13:01, Arnd Bergmann wrote: > If there is software that still relies on those hacks, it's > probably very old, and more likely to be on 32-bit systems. > There are many references to /dev/mem in Debian codesearch [1], > but it's usually related to pre-PCIe graphics (svgalib, XFree86, > uvesafb/v86), or it's memory-only accesses that rely on > !CONFIG_STRICT_DEVMEM to read kernel structures. > > Arnd > > [1] https://codesearch.debian.net/search?q=%2Fdev%2Fmem&literal=1&perpkg=1 I did basically the same exercise a week or two ago. I really didn't see any examples that concerned me. I completely agree that it looked very much limited to old, crusty code that either doesn't matter at _all_ or code that falls back to newer mechanisms on modern CONFIG_STRICT_DEVMEM=y systems.