linux-kernel - Re: [PATCH v2 04/21] x86/virt/tdx: Prepare to support P-SEAMLDR SEAMCALLs

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Message-ID: <526f295a-326c-4999-8078-53fb758759ef@linux.intel.com>
Date: Fri, 21 Nov 2025 15:53:46 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Chao Gao <chao.gao@...el.com>
Cc: linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org, x86@...nel.org,
 reinette.chatre@...el.com, ira.weiny@...el.com, kai.huang@...el.com,
 dan.j.williams@...el.com, yilun.xu@...ux.intel.com, sagis@...gle.com,
 vannapurve@...gle.com, paulmck@...nel.org, nik.borisov@...e.com,
 Farrah Chen <farrah.chen@...el.com>, "Kirill A. Shutemov" <kas@...nel.org>,
 Dave Hansen <dave.hansen@...ux.intel.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v2 04/21] x86/virt/tdx: Prepare to support P-SEAMLDR
 SEAMCALLs



On 10/1/2025 10:52 AM, Chao Gao wrote:
> P-SEAMLDR is another component alongside the TDX module within the
> protected SEAM range. P-SEAMLDR can update the TDX module at runtime.
> Software can talk with P-SEAMLDR via SEAMCALLs with the bit 63 of RAX
> (leaf number) set to 1 (a.k.a P-SEAMLDR SEAMCALLs).
>
> P-SEAMLDR SEAMCALLs differ from SEAMCALLs of the TDX module in terms of
> error codes and the handling of the current VMCS.
>
> In preparation for adding support for P-SEAMLDR SEAMCALLs, do the two
> following changes to SEAMCALL low-level helpers:
>
> 1) Tweak sc_retry() to retry on "lack of entropy" errors reported by
>     P-SEAMLDR because it uses a different error code.
>
> 2) Add seamldr_err() to log error messages on P-SEAMLDR SEAMCALL failures.
>
> Signed-off-by: Chao Gao <chao.gao@...el.com>
> Tested-by: Farrah Chen <farrah.chen@...el.com>
> ---
> Add seamldr_prerr() as a macro to be consistent with existing code. If
> maintainers would like to switch these to static inline functions then I
> would be happy to add a new patch to convert existing macros to static
> inline functions and build on that.
>
> v2:
>   - use a macro rather than an inline function for seamldr_err() for
>     consistency.
> ---
>   arch/x86/include/asm/tdx.h       |  5 +++++
>   arch/x86/virt/vmx/tdx/seamcall.h | 29 ++++++++++++++++++++++++++++-
>   2 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index e872a411a359..7ad026618a23 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -32,6 +32,11 @@
>   #define TDX_SUCCESS		0ULL
>   #define TDX_RND_NO_ENTROPY	0x8000020300000000ULL
>   
> +/* P-SEAMLDR SEAMCALL leaf function error codes */
> +#define SEAMLDR_RND_NO_ENTROPY	0x8000000000030001ULL
> +
> +#define SEAMLDR_SEAMCALL_MASK	_BITUL(63)
> +
>   #ifndef __ASSEMBLER__
>   
>   #include <uapi/asm/mce.h>
> diff --git a/arch/x86/virt/vmx/tdx/seamcall.h b/arch/x86/virt/vmx/tdx/seamcall.h
> index 71b6ffddfa40..3f462e58d68e 100644
> --- a/arch/x86/virt/vmx/tdx/seamcall.h
> +++ b/arch/x86/virt/vmx/tdx/seamcall.h
> @@ -14,6 +14,19 @@ u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
>   
>   typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
>   
> +static inline bool is_seamldr_call(u64 fn)
> +{
> +	return fn & SEAMLDR_SEAMCALL_MASK;
> +}
> +
> +static inline bool sc_need_retry(u64 fn, u64 error_code)
> +{
> +	if (is_seamldr_call(fn))

Comparing to TDX module seamcall, seamldr seamcall should be much less.
Maybe unlikely()?

> +		return error_code == SEAMLDR_RND_NO_ENTROPY;
> +	else
> +		return error_code == TDX_RND_NO_ENTROPY;
> +}
> +
>   static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
>   			   struct tdx_module_args *args)
>   {
> @@ -22,7 +35,7 @@ static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
>   
>   	do {
>   		ret = func(fn, args);
> -	} while (ret == TDX_RND_NO_ENTROPY && --retry);
> +	} while (sc_need_retry(fn, ret) && --retry);
>   
>   	return ret;
>   }
> @@ -48,6 +61,17 @@ static inline void seamcall_err_ret(u64 fn, u64 err,
>   			args->r9, args->r10, args->r11);
>   }
>   
> +static inline void seamldr_err(u64 fn, u64 err, struct tdx_module_args *args)
> +{
> +	/*
> +	 * Get the actual leaf number. No need to print the bit used to
> +	 * differentiate between P-SEAMLDR and TDX module as the "P-SEAMLDR"
> +	 * string in the error message already provides that information.
> +	 */
> +	fn &= ~SEAMLDR_SEAMCALL_MASK;
> +	pr_err("P-SEAMLDR (%lld) failed: 0x%016llx\n", fn, err);

%lld -> %llu ?

And 0x% -> %# to align with seamcall_err().



> +}
> +
>   static __always_inline int sc_retry_prerr(sc_func_t func,
>   					  sc_err_func_t err_func,
>   					  u64 fn, struct tdx_module_args *args)
> @@ -76,4 +100,7 @@ static __always_inline int sc_retry_prerr(sc_func_t func,
>   #define seamcall_prerr_ret(__fn, __args)					\
>   	sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
>   
> +#define seamldr_prerr(__fn, __args)						\
> +	sc_retry_prerr(__seamcall, seamldr_err, (__fn), (__args))
> +
>   #endif