Re: [PATCH v17 1/3] x86/tdx: Add a wrapper to get TDREPORT from the TDX Module

[Wander Lairson Costa]

On Thu, Nov 03, 2022 at 08:23:53PM -0700, Kuppuswamy Sathyanarayanan wrote:
> To support TDX attestation, the TDX guest driver exposes an IOCTL
> interface to allow userspace to get the TDREPORT from the TDX module
> via TDG.MR.TDREPORT TDCALL.
> 
> In order to get the TDREPORT in the TDX guest driver, instead of using
> a low level function like __tdx_module_call(), add a
> tdx_mcall_get_report() wrapper function to handle it.
> 
> This is a preparatory patch for adding attestation support.
> 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> ---
> 
> Changes since v16
>  * Added invalid operand error code support.
>  * Removed subtype param in tdx_mcall_get_report().
> 
> Changes since v15:
>  * None
> 
> Changes since v14:
>  * Instead of exporting __tdx_module_call(), added a new wrapper.
>  * Rebased on top of v6.1-rc1
> 
>  arch/x86/coco/tdx/tdx.c    | 38 ++++++++++++++++++++++++++++++++++++++
>  arch/x86/include/asm/tdx.h |  2 ++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 928dcf7a20d9..17cf2e9d5849 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -5,6 +5,8 @@
>  #define pr_fmt(fmt)     "tdx: " fmt
>  
>  #include <linux/cpufeature.h>
> +#include <linux/export.h>
> +#include <linux/io.h>
>  #include <asm/coco.h>
>  #include <asm/tdx.h>
>  #include <asm/vmx.h>
> @@ -15,6 +17,7 @@
>  /* TDX module Call Leaf IDs */
>  #define TDX_GET_INFO			1
>  #define TDX_GET_VEINFO			3
> +#define TDX_GET_REPORT			4
>  #define TDX_ACCEPT_PAGE			6
>  
>  /* TDX hypercall Leaf IDs */
> @@ -34,6 +37,10 @@
>  #define VE_GET_PORT_NUM(e)	((e) >> 16)
>  #define VE_IS_IO_STRING(e)	((e) & BIT(4))
>  
> +/* TDX Module call error codes */
> +#define TDCALL_RETURN_CODE(a)	((a) >> 32)
> +#define TDCALL_INVALID_OPERAND	0xc0000100
> +
>  /*
>   * Wrapper for standard use of __tdx_hypercall with no output aside from
>   * return code.
> @@ -98,6 +105,37 @@ static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
>  		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
>  }
>  
> +/**
> + * tdx_mcall_get_report() - Wrapper for TDG.MR.REPORT TDCALL.
> + * @reportdata: Address of the input buffer which contains
> + *              user-defined REPORTDATA to be included into
> + *              TDREPORT.
> + * @tdreport: Address of the output buffer to store TDREPORT.
> + *
> + * Generate TDREPORT using "TDG.MR.REPORT" TDCALL. Refer to section
> + * titled "TDG.MR.REPORT leaf" in the TDX Module 1.0 specification
> + * for detailed information. It is used in the TDX guest driver
> + * module to get the TDREPORT.
> + *
> + * Return 0 on success, -EINVAL for invalid operands, or -EIO on
> + * other TDCALL failures.
> + */
> +int tdx_mcall_get_report(u8 *reportdata, u8 *tdreport)
> +{
> +	u64 ret;
> +
> +	ret = __tdx_module_call(TDX_GET_REPORT, virt_to_phys(tdreport),
> +				virt_to_phys(reportdata), 0, 0, NULL);
> +	if (ret) {
> +		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
> +			return -EINVAL;
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(tdx_mcall_get_report);
> +
>  static u64 get_cc_mask(void)
>  {
>  	struct tdx_module_output out;
> diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
> index 020c81a7c729..eef9c0b7880e 100644
> --- a/arch/x86/include/asm/tdx.h
> +++ b/arch/x86/include/asm/tdx.h
> @@ -67,6 +67,8 @@ void tdx_safe_halt(void);
>  
>  bool tdx_early_handle_ve(struct pt_regs *regs);
>  
> +int tdx_mcall_get_report(u8 *reportdata, u8 *tdreport);
> +
>  #else
>  
>  static inline void tdx_early_init(void) { };
> -- 
> 2.34.1
> 
> 

Acked-by: Wander Lairson Costa <wander@xxxxxxxxxx>