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

[Kiryl Shutsemau <kas@kernel.org>]

On Mon, May 25, 2026 at 02:54:40PM +0800, Xiaoyao Li wrote:
> 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 ?

This is my read too. Looks like we need a separate step after
config_tdx_module() to readout config-dependatant metadata.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov