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

[Xiaoyao Li]

On 5/22/2026 11:41 AM, Xu Yilun wrote:
...
> +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);

Is it correct to read "memory_pool_required_pages" and "ext_required" so 
early in get_tdx_sys_info()? get_tdx_sys_info() is called before 
config_tdx_module() which calls TDH.SYS.CONFIG.

If I read the TDX module base spec correctly, the amount of memory for 
extensions and EXT_REQUIRED field depends on the enabled features, which 
is determined by TDH.SYS.CONFIG/TDH.SYS.UPDATE ?

>   	return ret;
>   }