Re: [PATCH 6/9] x86/virt/tdx: Start to track all global metadata in one structure

Nikolay Borisov
2024-06-18T13:17:49Z

On 16.06.24 г. 15:01 ч., Kai Huang wrote:
> The TDX module provides a set of "global metadata fields". They report
> 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_sysinfo' to track all
> global metadata fields.
>
> TDX categories global metadata fields into different "Class"es. E.g.,
> the current TDMR related fields are under class "TDMR Info". Instead of
> making 'struct tdx_sysinfo' 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 current construct_tdmr() can just
> take the structure which contains "TDMR Info" metadata fields.
>
> Start with moving 'struct tdx_tdmr_sysinfo' to 'struct tdx_sysinfo', and
> rename 'struct tdx_tdmr_sysinfo' to 'struct tdx_sysinfo_tdmr_info' to
> make it consistent with the "class name".
>
> Add a new function get_tdx_sysinfo() as the place to read all metadata
> fields, and call it at the beginning of init_tdx_module(). Move the
> existing get_tdx_tdmr_sysinfo() to get_tdx_sysinfo().
>
> Note there is a functional change: get_tdx_tdmr_sysinfo() is moved from
> after build_tdx_memlist() to before it, but it is fine to do so.

Why? I don't see build_tdx_memlist() using any tdmr data.

>
> Signed-off-by: Kai Huang <kai.huang@intel.com>

This patch semantically does 3 independent things :

1. Renames tdx_tdmr_sysinfo to tdx_sysinfo_tdmr_info
2. Introduces tdx_sysinfo and puts the aforementioned struct in it.
3. Moves get_tdx_tdmr_sysinfo

> ---
> arch/x86/virt/vmx/tdx/tdx.c | 29 +++++++++++++++++------------
> arch/x86/virt/vmx/tdx/tdx.h | 32 +++++++++++++++++++++++++-------
> 2 files changed, 42 insertions(+), 19 deletions(-)
>
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index fad42014ca37..4683884efcc6 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -320,11 +320,11 @@ static int stbuf_read_sysmd_multi(const struct field_mapping *fields,
> }
>
> #define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member) \
> - TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
> + TD_SYSINFO_MAP(_field_id, struct tdx_sysinfo_tdmr_info, _member)
>
> -static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> +static int get_tdx_tdmr_sysinfo(struct tdx_sysinfo_tdmr_info *tdmr_sysinfo)
> {
> - /* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
> + /* Map TD_SYSINFO fields into 'struct tdx_sysinfo_tdmr_info': */
> static const struct field_mapping fields[] = {
> TD_SYSINFO_MAP_TDMR_INFO(MAX_TDMRS, max_tdmrs),
> TD_SYSINFO_MAP_TDMR_INFO(MAX_RESERVED_PER_TDMR, max_reserved_per_tdmr),
> @@ -337,6 +337,11 @@ static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
> return stbuf_read_sysmd_multi(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
> }
>
> +static int get_tdx_sysinfo(struct tdx_sysinfo *sysinfo)

What's the point of this function, directly calling
get_tdx_tdmr_sysinfo(&sysinfo->tdmr_info); isn't any less obvious.

> +{
> + return get_tdx_tdmr_sysinfo(&sysinfo->tdmr_info);
> +}
> +
> /* Calculate the actual TDMR size */
> static int tdmr_size_single(u16 max_reserved_per_tdmr)
> {

<snip>