Re: [PATCH v5 16/22] x86/virt/tdx: Update tdx_sysinfo and check features post-update

[Kiryl Shutsemau]

On Sun, Mar 15, 2026 at 06:58:36AM -0700, Chao Gao wrote:
> tdx_sysinfo contains all metadata of the active TDX module, including
> versions, supported features, and TDMR/TDCS/TDVPS information etc. These
> values may change over updates. Blindly refreshing the entire tdx_sysinfo
> could disrupt running software, as it may subtly rely on the previous state
> unless proven otherwise.
> 
> Adopt a conservative approach, like microcode updates, by only refreshing
> version information that does not affect functionality, while ignoring
> all other changes. This is acceptable as new modules are required to
> maintain backward compatibility.
> 
> Any updates to metadata beyond versions should be justified and reviewed on
> a case-by-case basis.
> 
> Note that preallocating a tdx_sys_info buffer before updates is to avoid
> having to handle -ENOMEM when updating tdx_sysinfo after a successful
> update.
> 
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Reviewed-by: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
> Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>
> Reviewed-by: Kai Huang <kai.huang@xxxxxxxxx>
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>

Reviewed-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov