Re: [PATCH v2 03/21] x86/virt/tdx: Move low level SEAMCALL helpers out of <asm/tdx.h>

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

On 10/1/2025 10:52 AM, Chao Gao wrote:
> From: Kai Huang <kai.huang@intel.com>
>
> TDX host core code implements three seamcall*() helpers to make SEAMCALL
> to the TDX module.  Currently, they are implemented in <asm/tdx.h> and
> are exposed to other kernel code which includes <asm/tdx.h>.
>
> However, other than the TDX host core, seamcall*() are not expected to
> be used by other kernel code directly.  For instance, for all SEAMCALLs
> that are used by KVM, the TDX host core exports a wrapper function for
> each of them.
>
> Move seamcall*() and related code out of <asm/tdx.h> and make them only
> visible to TDX host core.
>
> Since TDX host core tdx.c is already very heavy, don't put low level
> seamcall*() code there but to a new dedicated "seamcall.h".  Also,
> currently tdx.c has seamcall_prerr*() helpers which additionally print
> error message when calling seamcall*() fails.  Move them to "seamcall.h"
> as well.  In such way all low level SEAMCALL helpers are in a dedicated
> place, which is much more readable.
>
> Signed-off-by: Kai Huang <kai.huang@intel.com>
> Signed-off-by: Chao Gao <chao.gao@intel.com>

Reviewed-by: Zhenzhong Duan <zhenzhong.duan@intel.com>

> ---
> v2:
>   - new
> ---
>   arch/x86/include/asm/tdx.h       | 24 ----------
>   arch/x86/virt/vmx/tdx/seamcall.h | 79 ++++++++++++++++++++++++++++++++
>   arch/x86/virt/vmx/tdx/tdx.c      | 46 +------------------
>   3 files changed, 80 insertions(+), 69 deletions(-)
>   create mode 100644 arch/x86/virt/vmx/tdx/seamcall.h
>
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index cbea169b5fa0..e872a411a359 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -97,31 +97,7 @@ static inline long tdx_kvm_hypercall(unsigned int nr, unsigned long p1,
>   #endif /* CONFIG_INTEL_TDX_GUEST && CONFIG_KVM_GUEST */
>   
>   #ifdef CONFIG_INTEL_TDX_HOST
> -u64 __seamcall(u64 fn, struct tdx_module_args *args);
> -u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
> -u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
>   void tdx_init(void);
> -
> -#include <asm/archrandom.h>
> -
> -typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
> -
> -static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
> -			   struct tdx_module_args *args)
> -{
> -	int retry = RDRAND_RETRY_LOOPS;
> -	u64 ret;
> -
> -	do {
> -		ret = func(fn, args);
> -	} while (ret == TDX_RND_NO_ENTROPY && --retry);
> -
> -	return ret;
> -}
> -
> -#define seamcall(_fn, _args)		sc_retry(__seamcall, (_fn), (_args))
> -#define seamcall_ret(_fn, _args)	sc_retry(__seamcall_ret, (_fn), (_args))
> -#define seamcall_saved_ret(_fn, _args)	sc_retry(__seamcall_saved_ret, (_fn), (_args))
>   int tdx_enable(void);
>   const char *tdx_dump_mce_info(struct mce *m);
>   const struct tdx_sys_info *tdx_get_sysinfo(void);
> diff --git a/arch/x86/virt/vmx/tdx/seamcall.h b/arch/x86/virt/vmx/tdx/seamcall.h
> new file mode 100644
> index 000000000000..71b6ffddfa40
> --- /dev/null
> +++ b/arch/x86/virt/vmx/tdx/seamcall.h
> @@ -0,0 +1,79 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Copyright (C) 2025 Intel Corporation */
> +#ifndef _X86_VIRT_SEAMCALL_H
> +#define _X86_VIRT_SEAMCALL_H
> +
> +#include <linux/printk.h>
> +#include <linux/types.h>
> +#include <asm/archrandom.h>
> +#include <asm/tdx.h>
> +
> +u64 __seamcall(u64 fn, struct tdx_module_args *args);
> +u64 __seamcall_ret(u64 fn, struct tdx_module_args *args);
> +u64 __seamcall_saved_ret(u64 fn, struct tdx_module_args *args);
> +
> +typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args);
> +
> +static __always_inline u64 sc_retry(sc_func_t func, u64 fn,
> +			   struct tdx_module_args *args)
> +{
> +	int retry = RDRAND_RETRY_LOOPS;
> +	u64 ret;
> +
> +	do {
> +		ret = func(fn, args);
> +	} while (ret == TDX_RND_NO_ENTROPY && --retry);
> +
> +	return ret;
> +}
> +
> +#define seamcall(_fn, _args)		sc_retry(__seamcall, (_fn), (_args))
> +#define seamcall_ret(_fn, _args)	sc_retry(__seamcall_ret, (_fn), (_args))
> +#define seamcall_saved_ret(_fn, _args)	sc_retry(__seamcall_saved_ret, (_fn), (_args))
> +
> +typedef void (*sc_err_func_t)(u64 fn, u64 err, struct tdx_module_args *args);
> +
> +static inline void seamcall_err(u64 fn, u64 err, struct tdx_module_args *args)
> +{
> +	pr_err("SEAMCALL (%llu) failed: %#016llx\n", fn, err);
> +}
> +
> +static inline void seamcall_err_ret(u64 fn, u64 err,
> +				    struct tdx_module_args *args)
> +{
> +	seamcall_err(fn, err, args);
> +	pr_err("RCX %#016llx RDX %#016llx R08 %#016llx\n",
> +			args->rcx, args->rdx, args->r8);
> +	pr_err("R09 %#016llx R10 %#016llx R11 %#016llx\n",
> +			args->r9, args->r10, args->r11);
> +}
> +
> +static __always_inline int sc_retry_prerr(sc_func_t func,
> +					  sc_err_func_t err_func,
> +					  u64 fn, struct tdx_module_args *args)
> +{
> +	u64 sret = sc_retry(func, fn, args);
> +
> +	if (sret == TDX_SUCCESS)
> +		return 0;
> +
> +	if (sret == TDX_SEAMCALL_VMFAILINVALID)
> +		return -ENODEV;
> +
> +	if (sret == TDX_SEAMCALL_GP)
> +		return -EOPNOTSUPP;
> +
> +	if (sret == TDX_SEAMCALL_UD)
> +		return -EACCES;
> +
> +	err_func(fn, sret, args);
> +	return -EIO;
> +}
> +
> +#define seamcall_prerr(__fn, __args)						\
> +	sc_retry_prerr(__seamcall, seamcall_err, (__fn), (__args))
> +
> +#define seamcall_prerr_ret(__fn, __args)					\
> +	sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
> +
> +#endif
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index f429a5fdced2..b367bb1d94ed 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -38,6 +38,7 @@
>   #include <asm/cpu_device_id.h>
>   #include <asm/processor.h>
>   #include <asm/mce.h>
> +#include "seamcall.h"
>   #include "tdx.h"
>   
>   static u32 tdx_global_keyid __ro_after_init;
> @@ -58,51 +59,6 @@ static LIST_HEAD(tdx_memlist);
>   
>   static struct tdx_sys_info tdx_sysinfo;
>   
> -typedef void (*sc_err_func_t)(u64 fn, u64 err, struct tdx_module_args *args);
> -
> -static inline void seamcall_err(u64 fn, u64 err, struct tdx_module_args *args)
> -{
> -	pr_err("SEAMCALL (%llu) failed: %#016llx\n", fn, err);
> -}
> -
> -static inline void seamcall_err_ret(u64 fn, u64 err,
> -				    struct tdx_module_args *args)
> -{
> -	seamcall_err(fn, err, args);
> -	pr_err("RCX %#016llx RDX %#016llx R08 %#016llx\n",
> -			args->rcx, args->rdx, args->r8);
> -	pr_err("R09 %#016llx R10 %#016llx R11 %#016llx\n",
> -			args->r9, args->r10, args->r11);
> -}
> -
> -static __always_inline int sc_retry_prerr(sc_func_t func,
> -					  sc_err_func_t err_func,
> -					  u64 fn, struct tdx_module_args *args)
> -{
> -	u64 sret = sc_retry(func, fn, args);
> -
> -	if (sret == TDX_SUCCESS)
> -		return 0;
> -
> -	if (sret == TDX_SEAMCALL_VMFAILINVALID)
> -		return -ENODEV;
> -
> -	if (sret == TDX_SEAMCALL_GP)
> -		return -EOPNOTSUPP;
> -
> -	if (sret == TDX_SEAMCALL_UD)
> -		return -EACCES;
> -
> -	err_func(fn, sret, args);
> -	return -EIO;
> -}
> -
> -#define seamcall_prerr(__fn, __args)						\
> -	sc_retry_prerr(__seamcall, seamcall_err, (__fn), (__args))
> -
> -#define seamcall_prerr_ret(__fn, __args)					\
> -	sc_retry_prerr(__seamcall_ret, seamcall_err_ret, (__fn), (__args))
> -
>   /*
>    * Do the module global initialization once and return its result.
>    * It can be done on any cpu.  It's always called with interrupts