linux-kernel - Re: [PATCH v3] x86/tdx: Dump TDX version During the TD Bootup

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Date:   Tue, 3 Oct 2023 06:26:45 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Yi Sun <yi.sun@...el.com>, kirill.shutemov@...ux.intel.com,
        linux-kernel@...r.kernel.org
Cc:     heng.su@...el.com, yi.sun@...ux.intel.com,
        Dongcheng Yan <dongcheng.yan@...el.com>
Subject: Re: [PATCH v3] x86/tdx: Dump TDX version During the TD Bootup



On 9/30/2023 9:11 AM, Yi Sun wrote:
> It is essential for TD users to be aware of the vendor and version of
> the current TDX. Additionally, they can reference the TDX version when
> reporting bugs or issues.
> 
> Furthermore, the applications or device drivers running in TD can achieve
> enhanced reliability and flexibility by following the TDX Module ABI
> specification, because there are significant differences between different
> versions of TDX, as mentioned in the "Intel® TDX Module Incompatibilities
> between v1.0 and v1.5" reference. Here are a few examples:
> 
> MSR Name		Index		Reason
> ----------------------------------------------
> IA32_UARCH_MISC_CTL	0x1B01		From v1.5
> IA32_ARCH_CAPABILITIES	0x010A		Changed in v1.5
> IA32_TSX_CTRL		0x0122		Changed in v1.5
> 
> CPUID Leaf	Sub-leaf	Reason
> ---------------------------------------
> 0x7		2		From v1.5
> 0x22		0		From v1.5
> 0x23		0~3		From v1.5
> 0x80000007	0		From v1.5
> 
> During TD initialization, the TDX version info can be obtained by calling
> TDG.SYS.RD. This will fetch the current version of TDX, including the major
> and minor version numbers and vendor ID.
> 
> The TDCALL TDG.SYS.RD originates from TDX version 1.5. If the error
> TDCALL_INVALID_OPERAND occurs, it should be treated as TDX version 1.0.
> 
> Co-developed-by: Dongcheng Yan <dongcheng.yan@...el.com>
> Signed-off-by: Dongcheng Yan <dongcheng.yan@...el.com>
> Signed-off-by: Yi Sun <yi.sun@...el.com>
> 
> diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
> index 1d6b863c42b0..052376d521d1 100644
> --- a/arch/x86/coco/tdx/tdx.c
> +++ b/arch/x86/coco/tdx/tdx.c
> @@ -37,6 +37,24 @@
>  
>  #define TDREPORT_SUBTYPE_0	0
>  
> +/*
> + * TDX metadata base field id, used by TDCALL TDG.SYS.RD
> + * See TDX ABI Spec section 3.3.2.3 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
> +
> +/*
> + * The global-scope metadata field via TDG.SYS.RD TDCALL
> + */
> +struct tdg_sys_info {
> +	u32 vendor_id;
> +	u16 major_version;
> +	u16 minor_version;
> +};
> +
>  /* Called from __tdx_hypercall() for unrecoverable failure */
>  noinstr void __tdx_hypercall_failed(void)
>  {
> @@ -757,10 +775,54 @@ static bool tdx_enc_status_change_finish(unsigned long vaddr, int numpages,
>  	return true;
>  }
>  
> +/*
> + * Parse the tdx module version info from the global-scope metadata fields.
> + */
> +static int tdg_get_sysinfo(struct tdg_sys_info *td_sys)
> +{
> +	struct tdx_module_output out;
> +	u64 ret;
> +
> +	if (!td_sys)
> +		return -EINVAL;
> +
> +	ret = __tdx_module_call(TDX_SYS_RD, 0, TDX_SYS_VENDOR_ID_FID, 0, 0,
> +				&out);
> +	if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
> +		goto version_1_0;
> +	else if (ret)
> +		return ret;

For this failure case, do you want to reset tdg_sys_info to some value like zero
or some constants to specify unknown?

> +
> +	td_sys->vendor_id = (u32)out.r8;
> +
> +	ret = __tdx_module_call(TDX_SYS_RD, 0, TDX_SYS_MAJOR_FID, 0, 0, &out);
> +	if (ret)
> +		return ret;
> +
> +	td_sys->major_version = (u16)out.r8;
> +
> +	ret = __tdx_module_call(TDX_SYS_RD, 0, TDX_SYS_MINOR_FID, 0, 0, &out);
> +	if (ret)
> +		return ret;
> +
> +	td_sys->minor_version = (u16)out.r8;
> +
> +	return 0;
> +
> +	/* TDX 1.0 does not have the TDCALL TDG.SYS.RD */
> +version_1_0:
> +	td_sys->vendor_id = TDX_VENDOR_INTEL;
> +	td_sys->major_version = 1;
> +	td_sys->minor_version = 0;
> +
> +	return 0;
> +}
> +
>  void __init tdx_early_init(void)
>  {
>  	u64 cc_mask;
>  	u32 eax, sig[3];
> +	struct tdg_sys_info td_sys_info;
>  
>  	cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2],  &sig[1]);
>  
> @@ -820,5 +882,9 @@ void __init tdx_early_init(void)
>  	 */
>  	x86_cpuinit.parallel_bringup = false;
>  
> -	pr_info("Guest detected\n");
> +	tdg_get_sysinfo(&td_sys_info);

Why not check the return value before dumping the info?

> +
> +	pr_info("Guest detected. TDX version:%u.%u VendorID: %x\n",
> +		td_sys_info.major_version, td_sys_info.minor_version,
> +		td_sys_info.vendor_id);
>  }
> diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
> index 7513b3bb69b7..10ecb5dece84 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -16,6 +16,7 @@
>  #define TDX_GET_REPORT			4
>  #define TDX_ACCEPT_PAGE			6
>  #define TDX_WR				8
> +#define TDX_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