From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.12]) (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 25FE412F584 for ; Fri, 17 May 2024 16:07:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.12 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715962080; cv=none; b=Nwm8m9Z5yk83vo3/RrwqwyUgNYqpGfTqwARhV856GCqp0DKnASSD4EP+ZBZcT7djtqNRJ8ZUt2f6U2pdiHS5b0G+A1wF3s3MX3a5uVoqWgEByxRRg47lpy4QletgKH/5xUt1cLxT0+Qz6RqkVtwEfLXO+/uLtkz0aH9nxmwTAYw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715962080; c=relaxed/simple; bh=J0ZrYaWrs/Vd5RrjpLaRO2cveV9VPuP6HI48xKjxsII=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=S44fxQZbR4dEfmM6i1OIsfvI86/u3xnVPl5YnHgSfnBWryvDWgM9mA+kwZLLiMZVatNrpFgeTEi4mpitSaW6VFmsQY0Rprh5Li2LbhYtNmdWUEYTpvaSARbyYb1CKXWCdN+Rcp9RsjEivdV6but3O1j2/w8VhtIRfnCciK24DUA= 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=BOY1QxpZ; arc=none smtp.client-ip=192.198.163.12 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="BOY1QxpZ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1715962079; x=1747498079; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=J0ZrYaWrs/Vd5RrjpLaRO2cveV9VPuP6HI48xKjxsII=; b=BOY1QxpZ/QSFwAECisaKR37Q3v1BhsT1Zaj1DxFIN89J6UMl+vXT7e4p kPWcLBalnWqtANWymTZ44a5dRh7M1JyhaOMKKgE57pHoil6den8bebrNS roTqPgpKFD8nR0dUlNh4cwbLnODRVOynRwsPJYALq6JuEusFpxHhBzT+M ZZ6AlksJerItMxD2NQWIptRaEmS9lrRqte2eXs1sxGSaWt5TkFqXb166H AGMqgYOKh+f9m0HL8EyhNrbh6PCCgnmc3YgjgrPWgkR1KPCLAYbYkgZoL 7NFBy4MNn8S17TXJS1C/u1AKWrqMX6klsHpDE6Fs3ovwWgfuTR0cvvCz3 w==; X-CSE-ConnectionGUID: e0kVIgWtTZeEErwpN1Jyfg== X-CSE-MsgGUID: jhLj+uFbQjWgSfjTnrQhdQ== X-IronPort-AV: E=McAfee;i="6600,9927,11075"; a="15977523" X-IronPort-AV: E=Sophos;i="6.08,168,1712646000"; d="scan'208";a="15977523" Received: from fmviesa003.fm.intel.com ([10.60.135.143]) by fmvoesa106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2024 09:07:56 -0700 X-CSE-ConnectionGUID: gqVsuMebTZeLgkuPO4ZITw== X-CSE-MsgGUID: saJ3jLV1Sby/Z/Pzubv2bA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.08,168,1712646000"; d="scan'208";a="36360534" Received: from kinlongk-mobl1.amr.corp.intel.com (HELO [10.125.108.204]) ([10.125.108.204]) by fmviesa003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 May 2024 09:07:55 -0700 Message-ID: <3a210286-7d0f-4404-ad79-c8eab1514381@intel.com> Date: Fri, 17 May 2024 09:07:54 -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 17/20] x86/tdx: Convert VM_RD/VM_WR tdcalls to use new TDCALL macros To: "Kirill A. Shutemov" , Sean Christopherson , Paolo Bonzini , Dave Hansen , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Josh Poimboeuf , Peter Zijlstra Cc: linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org References: <20240517141938.4177174-1-kirill.shutemov@linux.intel.com> <20240517141938.4177174-18-kirill.shutemov@linux.intel.com> Content-Language: en-US From: Dave Hansen 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: <20240517141938.4177174-18-kirill.shutemov@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Let's say you're debugging tdg_vm_rd(). You suspect someone read the spec wrong. You pull up the spec: https://sr71.net/~dave/intel/tdg.vm.rd.png On 5/17/24 07:19, Kirill A. Shutemov wrote: > static inline u64 tdg_vm_rd(u64 field, u64 *value) > { > - struct tdx_module_args args = { > - .rdx = field, > - }; RDX is assigned 'field'. Makes sense based on the input operands. > - u64 ret; > - > - ret = __tdcall_ret(TDG_VM_RD, &args)> - *value = args.r8; 'value' is set to r8. Also matches the spec. It's obvious that this is a 'two return values' pattern. > - return ret; This is also obviously correct. Compare that to: > + return TDCALL_1(TDG_VM_RD, 0, field, 0, 0, value); > } Where it's 100% opaque which registers thing to into or that 'value' is an output, not an input. So, yeah, this is fewer lines of C code. But it's *WAY* less self-documenting. It's harder to audit. It's harder to understand and it's more opaque. While the goals here are laudable, I'm not a big fan of the end result.