Re: [RFC PATCH 14/15] x86/virt/tdx: Embed version info in SEAMCALL leaf function definitions

[Xiaoyao Li <xiaoyao.li@intel.com>]

On 5/22/2026 11:41 AM, Xu Yilun wrote:
> Embed version information in SEAMCALL leaf function definitions rather
> than let the caller open code them. For now, only TDH.VP.INIT is
> involved.
> 
> Don't bother the caller to choose the SEAMCALL version if unnecessary.
> New version SEAMCALLs are guaranteed to be backward compatible, so
> ideally kernel doesn't need to keep version history and only uses the
> latest version SEAMCALLs.
> 
> The concern is some old TDX Modules don't recognize new version
> SEAMCALLs. Multiple SEAMCALL versions co-exist when kernel should
> support these old Modules. As time goes by, the old Modules deprecate
> and old version SEAMCALL definitions should disappear.
> 
> The old TDX Modules that only support TDH.VP.INIT v0 are all deprecated,
> so only provide the latest (v1) definition.
> 
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> ---
>   arch/x86/virt/vmx/tdx/tdx.h | 23 ++++++++++++++---------
>   arch/x86/virt/vmx/tdx/tdx.c |  4 ++--
>   2 files changed, 16 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
> index 01a7d7d8ada9..10aff23cd01f 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.h
> +++ b/arch/x86/virt/vmx/tdx/tdx.h
> @@ -2,6 +2,7 @@
>   #ifndef _X86_VIRT_TDX_H
>   #define _X86_VIRT_TDX_H
>   
> +#include <linux/bitfield.h>
>   #include <linux/bits.h>
>   
>   /*
> @@ -11,6 +12,18 @@
>    * architectural definitions come first.
>    */
>   
> +/*
> + * SEAMCALL leaf:
> + *
> + * Bit 15:0	Leaf number
> + * Bit 23:16	Version number
> + */
> +#define SEAMCALL_LEAF			GENMASK(15, 0)
> +#define SEAMCALL_VER			GENMASK(23, 16)
> +
> +#define SEAMCALL_LEAF_VER(l, v)		(FIELD_PREP(SEAMCALL_LEAF, l) | \
> +					 FIELD_PREP(SEAMCALL_VER, v))
> +
>   /*
>    * TDX module SEAMCALL leaf functions
>    */
> @@ -31,7 +44,7 @@
>   #define TDH_VP_CREATE			10
>   #define TDH_MNG_KEY_FREEID		20
>   #define TDH_MNG_INIT			21
> -#define TDH_VP_INIT			22
> +#define TDH_VP_INIT			SEAMCALL_LEAF_VER(22, 1)

how about

#define TDH_VP_INIT			22
#define TDH_VP_INIT_V1			SEAMCALL_LEAF_VER(TDH_VP_INIT, 1)

and use TDH_VP_INIT_V1 below?

>   #define TDH_PHYMEM_PAGE_RDMD		24
>   #define TDH_VP_RD			26
>   #define TDH_PHYMEM_PAGE_RECLAIM		28
> @@ -52,14 +65,6 @@
>   #define TDH_QUOTE_GET			98
>   #define TDH_QUOTE_INIT			100
>   
> -/*
> - * SEAMCALL leaf:
> - *
> - * Bit 15:0	Leaf number
> - * Bit 23:16	Version number
> - */
> -#define TDX_VERSION_SHIFT		16
> -
>   /* TDX page types */
>   #define	PT_NDA		0x0
>   #define	PT_RSVD		0x1
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 821f677e9a86..f7600f930c6e 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -2217,8 +2217,8 @@ u64 tdh_vp_init(struct tdx_vp *vp, u64 initial_rcx, u32 x2apicid)
>   		.r8 = x2apicid,
>   	};
>   
> -	/* apicid requires version == 1. */
> -	return seamcall(TDH_VP_INIT | (1ULL << TDX_VERSION_SHIFT), &args);
> +	/* apicid requires version == 1. See TDH_VP_INIT definition.*/
> +	return seamcall(TDH_VP_INIT, &args);
>   }
>   EXPORT_SYMBOL_FOR_KVM(tdh_vp_init);
>