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X-CSE-ConnectionGUID: b+goZj2VR/G4GLuxfQsdrA== X-CSE-MsgGUID: kZ8W0prGQCKzYd5nCUjdKQ== X-IronPort-AV: E=McAfee;i="6800,10657,11885"; a="99563286" X-IronPort-AV: E=Sophos;i="6.25,240,1779174000"; d="scan'208";a="99563286" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by orvoesa104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2026 08:15:41 -0700 X-CSE-ConnectionGUID: Gy2yMNMKSg2G0I5Z6ZxFKw== X-CSE-MsgGUID: GWZXmF2ySiWpFT14r//GXw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,240,1779174000"; d="scan'208";a="264411279" Received: from jmaxwel1-mobl.amr.corp.intel.com (HELO [10.125.108.191]) ([10.125.108.191]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Aug 2026 08:15:41 -0700 Message-ID: <22bf174e-788b-4038-84e0-c6bea351830d@intel.com> Date: Mon, 24 Aug 2026 08:15:41 -0700 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/6] x86/virt/tdx: Configure add-on features on TDX module init and update To: Xu Yilun Cc: x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, kas@kernel.org, rick.p.edgecombe@intel.com, yilun.xu@intel.com, xiaoyao.li@intel.com, sohil.mehta@intel.com, adrian.hunter@intel.com, kishen.maloor@intel.com, tony.lindgren@linux.intel.com, peter.fang@intel.com, baolu.lu@linux.intel.com, zhenzhong.duan@intel.com, chao.gao@intel.com, artem.bityutskiy@linux.intel.com, kvm@vger.kernel.org References: <20260821032920.256225-1-yilun.xu@linux.intel.com> <20260821032920.256225-3-yilun.xu@linux.intel.com> <27321cc1-5428-4590-a88d-b2824659c89a@intel.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 8/23/26 23:37, Xu Yilun wrote: > On Fri, Aug 21, 2026 at 07:38:42AM -0700, Dave Hansen wrote: >> On 8/20/26 20:29, Xu Yilun wrote: >>> static __init int tdx_sys_config(struct tdmr_info_pa_array *tdmr_pa_array, >>> - u64 nr_tdmr_pa, u64 global_keyid) >>> + u64 nr_tdmr_pa, u64 global_keyid, >>> + u64 addon_features0) >> >> addon_features0 is just a copy of the global, static, not changing >> get_tdx_addon_features0() return code, right? >> >> Why pass it around as a function argument? > > I thought that we need some place to explicitly see the TDX ABI > definition - what are the inputs the host should provide to the module. > > The addon_features0 is the *option* the host should provide to the > module according to the ABI. The global, static value for addon_features0 > is Linux's policy. So if we need to explicit the policy by the code, > this helper and its arguments are good places to show the boundary. > > But yes it does add boilerplate to the code, I can drop it. I'm not arguing that the helper should go away. What I'm seeing is this pattern: int helper() { return something; } int func_low_level(int arg) { // use arg } int func() { int foo = helper(); // use foo func_low_level(foo); } When it could use this pattern and just call helper() twice instead of obtaining its return value and passing it around: int helper() { return something; } int func_low_level() { int bar = helper(); // use bar } int func() { int foo = helper(); // use foo func_low_level(); } So that's what I was asking. Why pass the result of helper() around when you can just call helper() twice?