Re: [PATCH v4 20/24] x86/virt/tdx: Enable TDX Module runtime updates

[Huang, Kai]

On Thu, 2026-02-12 at 06:35 -0800, Chao Gao wrote:
> All pieces of TDX Module runtime updates are in place. Enable it if it
> is supported.
> 
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Reviewed-by: Xu Yilun <yilun.xu@xxxxxxxxxxxxxxx>
> Reviewed-by: Tony Lindgren <tony.lindgren@xxxxxxxxxxxxxxx>
> ---
> v4:
>  - s/BIT/BIT_ULL [Tony]
> ---
>  arch/x86/include/asm/tdx.h  | 5 ++++-
>  arch/x86/virt/vmx/tdx/tdx.h | 3 ---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index ffadbf64d0c1..ad62a7be0443 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -32,6 +32,9 @@
>  #define TDX_SUCCESS		0ULL
>  #define TDX_RND_NO_ENTROPY	0x8000020300000000ULL
>  
> +/* Bit definitions of TDX_FEATURES0 metadata field */
> +#define TDX_FEATURES0_TD_PRESERVING	BIT_ULL(1)
> +#define TDX_FEATURES0_NO_RBP_MOD	BIT_ULL(18)
>  #ifndef __ASSEMBLER__
>  
>  #include <uapi/asm/mce.h>
> @@ -105,7 +108,7 @@ const struct tdx_sys_info *tdx_get_sysinfo(void);
>  
>  static inline bool tdx_supports_runtime_update(const struct tdx_sys_info *sysinfo)
>  {
> -	return false; /* To be enabled when kernel is ready */
> +	return sysinfo->features.tdx_features0 & TDX_FEATURES0_TD_PRESERVING;
>  }
>  
>  int tdx_guest_keyid_alloc(void);
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index d1807a476d3b..749f4d74cb2c 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -88,9 +88,6 @@ struct tdmr_info {
>  	DECLARE_FLEX_ARRAY(struct tdmr_reserved_area, reserved_areas);
>  } __packed __aligned(TDMR_INFO_ALIGNMENT);
>  
> -/* Bit definitions of TDX_FEATURES0 metadata field */
> -#define TDX_FEATURES0_NO_RBP_MOD	BIT(18)
> -
> 

Nit:

Strictly speaking, moving this "NO_RBP_MOD" isn't required to "enable TDX
module runtime updates".  So I think it's better to call out in changelog
that this is trying to centralize the bit definitions.

Anyway, I think we have multiple series doing this so I guess things will
just sort out eventually.