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a="3220281" X-IronPort-AV: E=Sophos;i="6.27,207,1787036400"; d="scan'208";a="3220281" Received: from fmviesa013.fm.intel.com ([10.60.135.153]) by orvoesa113.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Nov 2026 19:57:07 -0800 X-CSE-ConnectionGUID: +8MGP+gYReaiQ6k3MS2Zhg== X-CSE-MsgGUID: dXsbyxssTFKDp7T4cpu9UQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,207,1787036400"; d="scan'208";a="10199240" Received: from yilunxu-optiplex-7050.sh.intel.com (HELO [127.0.1.1]) ([10.239.47.46]) by fmviesa013.fm.intel.com with ESMTP; 10 Nov 2026 19:57:03 -0800 From: Xu Yilun Date: Wed, 11 Nov 2026 11:48:43 +0800 Subject: [PATCH v5 2/6] x86/virt/tdx: Configure add-on features on TDX module init X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20261111-tdx-module-ext-v5-2-c74f764abc3d@linux.intel.com> References: <20261111-tdx-module-ext-v5-0-c74f764abc3d@linux.intel.com> In-Reply-To: <20261111-tdx-module-ext-v5-0-c74f764abc3d@linux.intel.com> To: x86@kernel.org, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org Cc: Kiryl Shutsemau , Rick Edgecombe , Dave Hansen , dave.hansen@intel.com, kvm@vger.kernel.org, yilun.xu@intel.com, yilun.xu@linux.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, nik.borisov@suse.com X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=4418; i=yilun.xu@linux.intel.com; h=from:subject:message-id; bh=1AgkZMDZ9wupKpCh5EP7vtfRDJS7fB/MjH80W+f07lc=; b=owGbwMvMwCH2Zztz45IFPbcYT6slMWR9frpcT+3Kz62Pk+aJHj+4I8rB083KUk9E0PJf0f3Fx jMusqmKdHSyMIhxMBiKKbIs8JjlNKV9FtPWTzuvwcxhZQIZIixTmZlTmqdXUeqQmVeSmqOXnJ/L wMUpAFN14xfDX7mMp1qHT235dnh6OuvMTYHT7Z4Iqs3c8tj4aNf5KUZ3J01jZFi7YH30efNPoQr 8jztCJ9/+s2VtjaOX4N3Mm/KvjriX63ICAA== X-Developer-Key: i=yilun.xu@linux.intel.com; a=openpgp; fpr=A612D44FA98BA699FECC642BE2C8D72186AC3949 The TDX architecture identifies some features that are off by default. They are classified as add-on features because enabling them affects existing TDX systems: they may change existing feature behavior, or reserve more memory. However, the impact of the first add-on features will be low enough to pursue a simple approach - the kernel just enables them when supported. If a feature with a very high overhead appears in the future, this can be revisited. The TDX module extends TDH.SYS.CONFIG with a new register argument to specify which add-on features to enable. This new argument is a bitmap that uses the same feature bits as TDX_FEATURES0. Note that Dynamic PAMT is an exception: although it is an add-on feature, it is controlled via a legacy, dedicated register argument [1]. Pass the bitmap of features that are supported by both kernel & TDX module to TDH.SYS.CONFIG. Initially, the bitmap is 0. It will be updated to contain specific feature bits as full kernel support lands. The TDX module requires leaf version 1 for TDH.SYS.CONFIG when passing the new bitmap argument. Set the version field to 1 if the argument is used to enable any add-on feature, otherwise keep the version as 0. This retains backward compatibility with older modules that don't recognize version 1. The original changelog was written by hand. AI was used to help correct grammatical errors and polish individual sentences for better readability. Signed-off-by: Xu Yilun Reviewed-by: Tony Lindgren Reviewed-by: Nikolay Borisov Reviewed-by: Rick Edgecombe Reviewed-by: Kiryl Shutsemau (Meta) Link: https://lore.kernel.org/all/20260904215841.303070-10-rick.p.edgecombe@intel.com/ # [1] --- v5: - Simplify the changelog, saved 5 lines - Better clarify the AI usage v4: - Add explanation why kernel enables add-on features solely on available support in the 3rd paragraph of the changelog. (Rick) - Collect Reviewed-by tags v3: - Update the stale changlog for bitmap arg of the wrapper (Chao) - s/get_tdx_addon_features0()/get_tdx_usable_addon_features0() (Tony) - Collect Reviewed-by tags v2: - Don't pass addon_features0 parameter around, get it in the wrappers (Dave) - Remove TDH.SYS.UPDATE wrapper (Dave & Rick) - Drop the changelog section explaining why add-on feature enabling is needed in this series, as it is a generally understood pattern (Rick) - Add a note in the changelog that Dynamic PAMT is not enabled via the new bitmap argument (Rick) - Add __init tag for get_tdx_addon_features0() (AI nitpicker) v1: - Use tdx_module_args.version to assign SEAMCALL leaf versions (Dave) - Remove DICE specific descriptions (Rick) - Remove the global var tdx_addon_features0 (Chao) - Add a Macro to collect kernel supported add-on feature bits (Rick) - Changelog & code comments change --- arch/x86/virt/vmx/tdx/tdx.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index c7bd0b01786d..3bfe78b4b538 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -1033,9 +1033,19 @@ static __init int construct_tdmrs(struct list_head *tmb_list, #define TDX_SYS_CONFIG_DYNAMIC_PAMT BIT(16) +/* List all kernel-supported add-on features0 bits here */ +#define TDX_KERNEL_SUPPORTED_ADDON_FEATURES0 (0) + +static __init u64 get_tdx_usable_addon_features0(void) +{ + return tdx_sysinfo.features.tdx_features0 & + TDX_KERNEL_SUPPORTED_ADDON_FEATURES0; +} + static __init int tdx_sys_config(u64 *tdmr_pa_array, unsigned int nr_tdmr_pa, u64 global_keyid) { + u64 addon_features0 = get_tdx_usable_addon_features0(); struct tdx_module_args args = { .rcx = __pa(tdmr_pa_array), .rdx = nr_tdmr_pa, @@ -1047,6 +1057,15 @@ static __init int tdx_sys_config(u64 *tdmr_pa_array, unsigned int nr_tdmr_pa, args.r8 |= TDX_SYS_CONFIG_DYNAMIC_PAMT; } + /* + * Use SEAMCALL version 1 that supports add-on features if any are + * requested. Otherwise use version 0 for backward compatibility. + */ + if (addon_features0) { + args.r9 = addon_features0; + args.version = 1; + } + return seamcall_prerr(TDH_SYS_CONFIG, &args); } -- 2.25.1