Re: [PATCH v3 5/8] x86/virt/tdx: Start to track all global metadata in one structure

[Adrian Hunter <adrian.hunter@intel.com>]

On 27/08/24 10:14, Kai Huang wrote:
> The TDX module provides a set of "global metadata fields".  They report

Global Metadata Fields

> things like TDX module version, supported features, and fields related
> to create/run TDX guests and so on.
> 
> Currently the kernel only reads "TD Memory Region" (TDMR) related fields
> for module initialization.  There are immediate needs which require the
> TDX module initialization to read more global metadata including module
> version, supported features and "Convertible Memory Regions" (CMRs).
> 
> Also, KVM will need to read more metadata fields to support baseline TDX
> guests.  In the longer term, other TDX features like TDX Connect (which
> supports assigning trusted IO devices to TDX guest) may also require
> other kernel components such as pci/vt-d to access global metadata.
> 
> To meet all those requirements, the idea is the TDX host core-kernel to
> to provide a centralized, canonical, and read-only structure for the
> global metadata that comes out from the TDX module for all kernel
> components to use.
> 
> As the first step, introduce a new 'struct tdx_sys_info' to track all
> global metadata fields.
> 
> TDX categories global metadata fields into different "Class"es.  E.g.,

"Classes"

> the TDMR related fields are under class "TDMR Info".  Instead of making
> 'struct tdx_sys_info' a plain structure to contain all metadata fields,
> organize them in smaller structures based on the "Class".
> 
> This allows those metadata fields to be used in finer granularity thus
> makes the code more clear.  E.g., the construct_tdmr() can just take the
> structure which contains "TDMR Info" metadata fields.
> 
> Add a new function get_tdx_sys_info() as the placeholder to read all
> metadata fields, and call it at the beginning of init_tdx_module().  For
> now it only calls get_tdx_sys_info_tdmr() to read TDMR related fields.
> 
> Note there is a functional change: get_tdx_sys_info_tdmr() is moved from
> after build_tdx_memlist() to before it, but it is fine to do so.
> 
> Signed-off-by: Kai Huang <kai.huang@intel.com>

Notwithstanding minor cosmetic tweaks:

Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
> 
> v2 -> v3:
>  - Split out the part to rename 'struct tdx_tdmr_sysinfo' to 'struct
>    tdx_sys_info_tdmr'.
> 
> 
> ---
>  arch/x86/virt/vmx/tdx/tdx.c | 19 ++++++++++++-------
>  arch/x86/virt/vmx/tdx/tdx.h | 36 +++++++++++++++++++++++++++++-------
>  2 files changed, 41 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 1cd9035c783f..24eb289c80e8 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -318,6 +318,11 @@ static int get_tdx_sys_info_tdmr(struct tdx_sys_info_tdmr *sysinfo_tdmr)
>  	return ret;
>  }
>  
> +static int get_tdx_sys_info(struct tdx_sys_info *sysinfo)
> +{
> +	return get_tdx_sys_info_tdmr(&sysinfo->tdmr);
> +}
> +
>  /* Calculate the actual TDMR size */
>  static int tdmr_size_single(u16 max_reserved_per_tdmr)
>  {
> @@ -1090,9 +1095,13 @@ static int init_tdmrs(struct tdmr_info_list *tdmr_list)
>  
>  static int init_tdx_module(void)
>  {
> -	struct tdx_sys_info_tdmr sysinfo_tdmr;
> +	struct tdx_sys_info sysinfo;
>  	int ret;
>  
> +	ret = get_tdx_sys_info(&sysinfo);
> +	if (ret)
> +		return ret;
> +
>  	/*
>  	 * To keep things simple, assume that all TDX-protected memory
>  	 * will come from the page allocator.  Make sure all pages in the
> @@ -1109,17 +1118,13 @@ static int init_tdx_module(void)
>  	if (ret)
>  		goto out_put_tdxmem;
>  
> -	ret = get_tdx_sys_info_tdmr(&sysinfo_tdmr);
> -	if (ret)
> -		goto err_free_tdxmem;
> -
>  	/* Allocate enough space for constructing TDMRs */
> -	ret = alloc_tdmr_list(&tdx_tdmr_list, &sysinfo_tdmr);
> +	ret = alloc_tdmr_list(&tdx_tdmr_list, &sysinfo.tdmr);
>  	if (ret)
>  		goto err_free_tdxmem;
>  
>  	/* Cover all TDX-usable memory regions in TDMRs */
> -	ret = construct_tdmrs(&tdx_memlist, &tdx_tdmr_list, &sysinfo_tdmr);
> +	ret = construct_tdmrs(&tdx_memlist, &tdx_tdmr_list, &sysinfo.tdmr);
>  	if (ret)
>  		goto err_free_tdmrs;
>  
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 8aabd03d8bf5..4cddbb035b9f 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -100,13 +100,6 @@ struct tdx_memblock {
>  	int nid;
>  };
>  
> -/* "TDMR info" part of "Global Scope Metadata" for constructing TDMRs */
> -struct tdx_sys_info_tdmr {
> -	u16 max_tdmrs;
> -	u16 max_reserved_per_tdmr;
> -	u16 pamt_entry_size[TDX_PS_NR];
> -};
> -
>  /* Warn if kernel has less than TDMR_NR_WARN TDMRs after allocation */
>  #define TDMR_NR_WARN 4
>  
> @@ -119,4 +112,33 @@ struct tdmr_info_list {
>  	int max_tdmrs;	/* How many 'tdmr_info's are allocated */
>  };
>  
> +/*
> + * Kernel-defined structures to contain "Global Scope Metadata".
> + *
> + * TDX global metadata fields are categorized by "Class"es.  See the

"Classes"

> + * "global_metadata.json" in the "TDX 1.5 ABI Definitions".
> + *
> + * 'struct tdx_sys_info' is the main structure to contain all metadata
> + * used by the kernel.  It contains sub-structures with each reflecting
> + * the "Class" in the 'global_metadata.json'.
> + *
> + * Note the structure name may not exactly follow the name of the
> + * "Class" in the TDX spec, but the comment of that structure always
> + * reflect that.
> + *
> + * Also note not all metadata fields in each class are defined, only
> + * those used by the kernel are.
> + */
> +
> +/* Class "TDMR info" */
> +struct tdx_sys_info_tdmr {
> +	u16 max_tdmrs;
> +	u16 max_reserved_per_tdmr;
> +	u16 pamt_entry_size[TDX_PS_NR];
> +};
> +
> +struct tdx_sys_info {
> +	struct tdx_sys_info_tdmr tdmr;
> +};
> +
>  #endif