Re: [RFC PATCH 15/15] x86/virt/tdx: Enable TDX Quoting extension

[Kishen Maloor <kishen.maloor@intel.com>]

On 5/21/26 8:41 PM, Xu Yilun wrote:
> From: Peter Fang <peter.fang@intel.com>
> 
> Enable the TDX Quoting feature via TDH.SYS.CONFIG when supported by the
> TDX module.
> 
> The TDX Quoting extension generates TDX attestation Quotes via a
> SEAMCALL, without using a discrete Quoting engine.
> 
> TDX Module supports add-on TDX features (e.g. TDX Quoting & TDX Module
> Extensions) that should be manually enabled by host. It extends
> TDH.SYS.CONFIG for host to choose to enable them on bootup.
> 
> Call TDH.SYS.CONFIG with a new bitmap input parameter to specify which
> features to enable. The bitmap uses the same definitions as
> TDX_FEATURES0. But note not all bits in TDX_FEATURES0 are valid for
> configuration, e.g. TDX Module Extensions is a service that supports TDX
> Quoting, it is implicitly enabled when TDX Quoting is enabled. Setting
> TDX_FEATURES0_EXT in the bitmap has no effect.
> 
> TDX Module advances the version of TDH.SYS.CONFIG for the change, so
> use the latest version (v1) for add-on feature enabling. But supporting
> existing Modules which only support v0 is still necessary until they are
> deprecated. In fact, it is unlikely that TDH.SYS.CONFIG ever needs to
> change again and the code would stay in v1. So there is little value
> in worrying about deprecating v0 to save a couple lines of code in 5-7
> years when these original TDX platforms sunset.
> 
> TDX Module updates global metadata when add-on features are enabled.
> Host should update the cached tdx_sysinfo to reflect these changes.
> 
> Co-developed-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Peter Fang <peter.fang@intel.com>
> ---
>   arch/x86/virt/vmx/tdx/tdx.h |  4 +++-
>   arch/x86/virt/vmx/tdx/tdx.c | 24 ++++++++++++++++++++++--
>   2 files changed, 25 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 10aff23cd01f..524a14c01aa6 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -58,7 +58,8 @@
>   #define TDH_PHYMEM_CACHE_WB		40
>   #define TDH_PHYMEM_PAGE_WBINVD		41
>   #define TDH_VP_WR			43
> -#define TDH_SYS_CONFIG			45
> +#define TDH_SYS_CONFIG_V0		45

Is it necessary to add _Vx macros when multiple versions can co-exist?

Just wondering if it would be cleaner in the following way?

- Leave the macros set at the current (non-deprecated) baseline version.
- Select vX using SEAMCALL_LEAF_VER() in config_tdx_module() when a vX feature
   is enabled.

u64 seamcall_fn = TDH_SYS_CONFIG;
...
if (tdx_sysinfo.features.tdx_features0 & TDX_FEATURES0_QUOTE) {
...
     seamcall_fn = SEAMCALL_LEAF_VER(TDH_SYS_CONFIG, 1);

> +#define TDH_SYS_CONFIG			SEAMCALL_LEAF_VER(TDH_SYS_CONFIG_V0, 1)
>   #define TDH_EXT_INIT			60
>   #define TDH_EXT_MEM_ADD			61
>   #define TDH_SYS_DISABLE			69
> @@ -97,6 +98,7 @@ struct tdmr_info {
>   /* Bit definitions of TDX_FEATURES0 metadata field */
>   #define TDX_FEATURES0_NO_RBP_MOD	BIT(18)
>   #define TDX_FEATURES0_EXT		BIT_ULL(39)
> +#define TDX_FEATURES0_QUOTE		BIT_ULL(50)
>   
>   /*
>    * Do not put any hardware-defined TDX structure representations below
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index f7600f930c6e..86e5b7ad19b3 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -1049,6 +1049,7 @@ static __init int construct_tdmrs(struct list_head *tmb_list,
>   static __init int config_tdx_module(struct tdmr_info_list *tdmr_list,
>   				    u64 global_keyid)
>   {
> +	u64 seamcall_fn = TDH_SYS_CONFIG_V0;
>   	struct tdx_module_args args = {};
>   	u64 *tdmr_pa_array;
>   	size_t array_sz;
> @@ -1074,8 +1075,22 @@ static __init int config_tdx_module(struct tdmr_info_list *tdmr_list,
>   	args.rcx = __pa(tdmr_pa_array);
>   	args.rdx = tdmr_list->nr_consumed_tdmrs;
>   	args.r8 = global_keyid;
> -	ret = seamcall_prerr(TDH_SYS_CONFIG, &args);
>   
> +	if (tdx_sysinfo.features.tdx_features0 & TDX_FEATURES0_QUOTE) {
> +		args.r9 |= TDX_FEATURES0_QUOTE;
> +		/* These parameters require version >= 1 */
> +		seamcall_fn = TDH_SYS_CONFIG;
> +	}
> +
> +	ret = seamcall_prerr(seamcall_fn, &args);
> +	if (ret)
> +		goto free_tdmr;
> +
> +	/* enabling TDX Quoting may change tdx_sysinfo, update it */
> +	if (tdx_sysinfo.features.tdx_features0 & TDX_FEATURES0_QUOTE)
> +		ret = get_tdx_sys_info(&tdx_sysinfo);
> +
> +free_tdmr:
>   	/* Free the array as it is not required anymore. */
>   	kfree(tdmr_pa_array);
>   
> @@ -1384,12 +1399,17 @@ static void tdx_quote_init(void)
>   	unsigned int nr_quote_pages;
>   	u64 r;
>   
> +	if (!(tdx_sysinfo.features.tdx_features0 & TDX_FEATURES0_QUOTE))
> +		return;
> +
>   	do {
>   		r = seamcall(TDH_QUOTE_INIT, &args);
>   	} while (r == TDX_INTERRUPTED_RESUMABLE);
>   
> -	if (r)
> +	if (r) {
> +		pr_err("Failed to enable quoting extension: 0x%llx\n", r);
>   		return;
> +	}
>   
>   	/* Quoting metadata is valid only after initialization */
>   	if (get_tdx_sys_info_quote(&tdx_sysinfo.quote))