Re: [PATCH v2 06/21] x86/virt/seamldr: Retrieve P-SEAMLDR information

["Duan, Zhenzhong" <zhenzhong.duan@intel.com>]

On 10/1/2025 10:52 AM, Chao Gao wrote:
> P-SEAMLDR returns its information e.g., version and supported features, in
> response to the SEAMLDR.INFO SEAMCALL.
>
> This information is useful for userspace. For example, the admin can decide
> which TDX module versions are compatible with the P-SEAMLDR according to
> the P-SEAMLDR version.
>
> Add and export seamldr_get_info() which retrieves P-SEAMLDR information by
> invoking SEAMLDR.INFO SEAMCALL in preparation for exposing P-SEAMLDR
> version and other necessary information to userspace.
>
> Signed-off-by: Chao Gao <chao.gao@intel.com>
> Tested-by: Farrah Chen <farrah.chen@intel.com>
> ---
>   arch/x86/include/asm/seamldr.h  | 27 +++++++++++++++++++++++++++
>   arch/x86/virt/vmx/tdx/seamldr.c | 17 ++++++++++++++++-
>   2 files changed, 43 insertions(+), 1 deletion(-)
>   create mode 100644 arch/x86/include/asm/seamldr.h
>
> diff --git a/arch/x86/include/asm/seamldr.h b/arch/x86/include/asm/seamldr.h
> new file mode 100644
> index 000000000000..d1e9f6e16e8d
> --- /dev/null
> +++ b/arch/x86/include/asm/seamldr.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_X86_SEAMLDR_H
> +#define _ASM_X86_SEAMLDR_H
> +
> +#include <linux/types.h>
> +
> +struct seamldr_info {
> +	u32	version;
> +	u32	attributes;
> +	u32	vendor_id;
> +	u32	build_date;
> +	u16	build_num;
> +	u16	minor_version;
> +	u16	major_version;
> +	u16	update_version;
> +	u8	reserved0[4];
> +	u32	num_remaining_updates;
> +	u8	reserved1[224];
> +} __packed;
> +
> +#ifdef CONFIG_INTEL_TDX_MODULE_UPDATE
> +const struct seamldr_info *seamldr_get_info(void);
> +#else
> +static inline const struct seamldr_info *seamldr_get_info(void) { return NULL; }
> +#endif
> +
> +#endif
> diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
> index b99d73f7bb08..08c2e3fe6071 100644
> --- a/arch/x86/virt/vmx/tdx/seamldr.c
> +++ b/arch/x86/virt/vmx/tdx/seamldr.c
> @@ -9,9 +9,16 @@
>   #include <linux/irqflags.h>
>   #include <linux/types.h>
>   
> +#include <asm/seamldr.h>
> +
>   #include "seamcall.h"
>   
> -static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
> +/* P-SEAMLDR SEAMCALL leaf function */
> +#define P_SEAMLDR_INFO			0x8000000000000000
> +
> +static struct seamldr_info seamldr_info __aligned(256);
> +
> +static inline int seamldr_call(u64 fn, struct tdx_module_args *args)
>   {
>   	unsigned long flags;
>   	u64 vmcs;
> @@ -54,3 +61,11 @@ static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
>   	WARN_ONCE(1, "Failed to save/restore the current VMCS");
>   	return -EIO;
>   }
> +
> +const struct seamldr_info *seamldr_get_info(void)
> +{
> +	struct tdx_module_args args = { .rcx = __pa(&seamldr_info) };
> +
> +	return seamldr_call(P_SEAMLDR_INFO, &args) ? NULL : &seamldr_info;
> +}
> +EXPORT_SYMBOL_GPL_FOR_MODULES(seamldr_get_info, "tdx-host");
We can trigger seamldr call once and cache the result except seamldr 
itself could be updated.