Re: [PATCH 01/15] x86/virt/tdx: Read global metadata for TDX Module Extensions

[Adrian Hunter]

On 22/05/2026 06:41, Xu Yilun wrote:
> Add reading of the global metadata for TDX Module Extensions.

For tip, isn't the expectation to explain the context first.  The
very first patch, might be a good place to explain a bit about
TDX Module Extensions in general.

> 
> TDX Module Extensions is an add-on feature enumerated by TDX_FEATURES0.
> But for the Module's integrity, Linux requires that all features that a
> Module advertises must have a complete, valid set of metadata, and the
> validation must succeed at core TDX initialization time.
> 
> Check TDX_FEATURES0 before reading these metadata. If a feature is
> advertised, a failure in reading associated metadata causes the entire
> TDX initialization to fail, otherwise skip.
> 
> Signed-off-by: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/include/asm/tdx_global_metadata.h  |  6 ++++++
>  arch/x86/virt/vmx/tdx/tdx.h                 |  1 +
>  arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 16 ++++++++++++++++
>  3 files changed, 23 insertions(+)
> 
> diff --git a/arch/x86/include/asm/tdx_global_metadata.h b/arch/x86/include/asm/tdx_global_metadata.h
> index 40689c8dc67e..533afe50a3f1 100644
> --- a/arch/x86/include/asm/tdx_global_metadata.h
> +++ b/arch/x86/include/asm/tdx_global_metadata.h
> @@ -40,12 +40,18 @@ struct tdx_sys_info_td_conf {
>  	u64 cpuid_config_values[128][2];
>  };
>  
> +struct tdx_sys_info_ext {
> +	u16 memory_pool_required_pages;
> +	u8 ext_required;
> +};
> +
>  struct tdx_sys_info {
>  	struct tdx_sys_info_version version;
>  	struct tdx_sys_info_features features;
>  	struct tdx_sys_info_tdmr tdmr;
>  	struct tdx_sys_info_td_ctrl td_ctrl;
>  	struct tdx_sys_info_td_conf td_conf;
> +	struct tdx_sys_info_ext ext;
>  };
>  
>  #endif
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index e2cf2dd48755..a5eec8e3cc71 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -87,6 +87,7 @@ 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)
>  
>  /*
>   * Do not put any hardware-defined TDX structure representations below
> diff --git a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
> index c7db393a9cfb..3d3b56ef3d2f 100644
> --- a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
> +++ b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
> @@ -100,6 +100,19 @@ static __init int get_tdx_sys_info_td_conf(struct tdx_sys_info_td_conf *sysinfo_
>  	return ret;
>  }
>  
> +static __init int get_tdx_sys_info_ext(struct tdx_sys_info_ext *sysinfo_ext)
> +{
> +	int ret = 0;
> +	u64 val;
> +
> +	if (!ret && !(ret = read_sys_metadata_field(0x3100000100000000, &val)))
> +		sysinfo_ext->memory_pool_required_pages = val;
> +	if (!ret && !(ret = read_sys_metadata_field(0x3100000000000001, &val)))
> +		sysinfo_ext->ext_required = val;
> +
> +	return ret;
> +}
> +
>  static __init int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
>  {
>  	int ret = 0;
> @@ -116,5 +129,8 @@ static __init int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
>  	ret = ret ?: get_tdx_sys_info_td_ctrl(&sysinfo->td_ctrl);
>  	ret = ret ?: get_tdx_sys_info_td_conf(&sysinfo->td_conf);
>  
> +	if (sysinfo->features.tdx_features0 & TDX_FEATURES0_EXT)
> +		ret = ret ?: get_tdx_sys_info_ext(&sysinfo->ext);
> +
>  	return ret;
>  }