Re: [PATCH v6] x86/tdx: Dump TDX Version During TD Bootup

[Kuppuswamy Sathyanarayanan]

On 10/21/2023 11:31 PM, Yi Sun wrote:
> Different versions of TDX have significant differences, as stated in the
> "Intel® TDX Module Incompatibilities between v1.0 and v1.5" reference.
> 
> It would be useful for TD users to be aware of the vendor and version of
> the current TDX in use. Users could expect different results when checking
> CPIUD or reading MSR in the user space, depending on the TDX version.
> Additionally, refer to the TDX version when reporting issues.
> 
> Reviewed-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
> Co-developed-by: Dongcheng Yan <dongcheng.yan@xxxxxxxxx>
> Signed-off-by: Dongcheng Yan <dongcheng.yan@xxxxxxxxx>
> Signed-off-by: Yi Sun <yi.sun@xxxxxxxxx>
> 
> ---
> V5 -> V6:
> 	- Remove random warnings at each step. Print the error details and
> 	presumed TDX version in common code. (Dave Hansen)
> 
> 	- Remove useless assignment and cast. Re-zeroed the input args
> 	between tdcalls. Refine the comments. (Dave Hansen)
> 
> V4 -> V5:
> 	- Print the version info inside the function detect_tdx_version, but
> 	not tdx_early_init(). Remove the structure tdg_sys_info, but have 3
> 	local variables instead. (Huang, Kai)
> 
> V3 -> V4: 
> 	- Rebase the patch on top of the latest tip tree. (Huang, Kai)
> 	- Change the return value of function tdg_get_sysinfo as void, and
> 	zero out tdg_sys_info when error occurs. (Kuppuswamy Sathyanarayanan)
> 
> V2 -> V3: 
> 	- Move the allocation of struct tdg_sys_info on stack inside
> 	tdx_early_init() and pass down to tdg_get_sysinfo() to fill.
> 	(Kirill Shutemov)
> 
> V1 -> V2: 
> 	- Move the defination of field IDs and the struct tdg_sys_info to tdx.c.
> 	(Kuppuswamy Sathyanarayanan)
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 3e6dbd2199cf..20e911241e56 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -37,6 +37,15 @@
>  
>  #define TDREPORT_SUBTYPE_0	0
>  
> +/*
> + * TDX metadata base field id, used by TDCALL TDG.SYS.RD
> + * See TDX ABI Spec Global Metadata Fields
> + */
> +#define TDX_SYS_VENDOR_ID_FID		0x0800000200000000ULL
> +#define TDX_SYS_MINOR_FID		0x0800000100000003ULL
> +#define TDX_SYS_MAJOR_FID		0x0800000100000004ULL
> +#define TDX_VENDOR_INTEL		0x8086
> +
>  /* Called from __tdx_hypercall() for unrecoverable failure */
>  noinstr void __noreturn __tdx_hypercall_failed(void)
>  {
> @@ -800,6 +809,56 @@ static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages,
>  	return true;
>  }
>  
> +/*
> + * Detect TDX Module version info from TDG.SYS.RD TDCALL
> + */
> +static void detect_tdx_version(void)
> +{
> +	struct tdx_module_args args = {};
> +	u16 major_version = 0;
> +	u16 minor_version = 0;
> +	u32 vendor_id = 0;
> +	u64 ret = 0;

Since you overwrite all above values, I think you can skip initialization.

> +
> +	args.rdx = TDX_SYS_VENDOR_ID_FID;
> +	ret = __tdcall_ret(TDG_SYS_RD, &args);
> +	if (ret)
> +		goto err_out;
> +
> +	vendor_id = args.r8;
> +
> +	memset(&args, 0, sizeof(args));
> +	args.rdx = TDX_SYS_MAJOR_FID;
> +	ret = __tdcall_ret(TDG_SYS_RD, &args);
> +	if (ret)
> +		goto err_out;
> +
> +	major_version = args.r8;
> +
> +	memset(&args, 0, sizeof(args));
> +	args.rdx = TDX_SYS_MINOR_FID;
> +	ret = __tdcall_ret(TDG_SYS_RD, &args);
> +	if (ret)
> +		goto err_out;
> +
> +	minor_version = args.r8;
> +
> +	pr_info("TDX detected. TDX version:%u.%u VendorID:%x\n",
> +		major_version, minor_version, vendor_id);

Since TDX prefix is part of pr_info, you can just use "Guest detected. version:..."

> +
> +	return;
> +
> +err_out:
> +	if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
> +		pr_info("TDG.SYS.RD not available\n");
> +	else
> +		pr_info("TDG.SYS.RD unknown error (%llu), reading field %llu\n",
> +			ret, args.rdx);
> +
> +	pr_info("Assuming TDX version:1.x (x<5) VendorID:%x\n",
> +		TDX_VENDOR_INTEL);
> +}
> +
>  void __init tdx_early_init(void)
>  {
>  	struct tdx_module_args args = {
> @@ -867,5 +926,5 @@ void __init tdx_early_init(void)
>  	 */
>  	x86_cpuinit.parallel_bringup = false;
>  
> -	pr_info("Guest detected\n");
> +	detect_tdx_version();
>  }
> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index f74695dea217..10b6c61e835e 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -17,6 +17,8 @@
>  #define TDG_MR_REPORT			4
>  #define TDG_MEM_PAGE_ACCEPT		6
>  #define TDG_VM_WR			8
> +/* The TDCALL TDG.SYS.RD originates from TDX version 1.5 */
> +#define TDG_SYS_RD			11
>  
>  /* TDCS fields. To be used by TDG.VM.WR and TDG.VM.RD module calls */
>  #define TDCS_NOTIFY_ENABLES		0x9100000000000010

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer