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Message-ID: <cf7360cb-6e9b-4550-8179-44bfc3a6e1b2@linux.intel.com>
Date: Sun, 8 Oct 2023 18:23:41 -0700
From: Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>
To: Yi Sun <yi.sun@...el.com>, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de, dave.hansen@...ux.intel.com, peterz@...radead.org,
x86@...nel.org
Cc: kirill.shutemov@...ux.intel.com, kai.huang@...el.com,
linux-kernel@...r.kernel.org, heng.su@...el.com,
yi.sun@...ux.intel.com, Dongcheng Yan <dongcheng.yan@...el.com>
Subject: Re: [PATCH v4] x86/tdx: Dump TDX version During the TD Bootup
On 10/5/2023 11:28 PM, 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.
>
> If the __tdcall_ret fails, expect a zero value for all tdx sys info.
> No additional error code is necessary to avoid introducing noise during
> the bootup.
>
> 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 3e6dbd2199cf..991f7dc695bd 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
> + */
I think you can just say "struct used to cache TDX Module version info"
> +struct tdg_sys_info {
> + u32 vendor_id;
> + u16 major_version;
> + u16 minor_version;
> +};
> +
> /* Called from __tdx_hypercall() for unrecoverable failure */
> noinstr void __noreturn __tdx_hypercall_failed(void)
> {
> @@ -800,6 +818,60 @@ 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.
> + *
> + * Refer to Intel TDX Application Binary Interface (ABI) section
> + * "TDG.SYS.RD".
> + */
How about "Parse TDX Module version info from TDG.SYS.RD TDCALL"?
> +static void tdg_get_sysinfo(struct tdg_sys_info *td_sys)
> +{
> + u64 ret;
> + struct tdx_module_args args = {
> + .rdx = TDX_SYS_VENDOR_ID_FID,
> + };
> +
> + if (!td_sys)
> + return;
This check can be removed. It will never be NULL as per current usage.
> +
> + memset(td_sys, 0, sizeof(struct tdg_sys_info));
> +
> + /*
> + * TDCALL leaf TDX_SYS_RD
> + * Input Field Identifier via RDX and get the output via R8.
> + */
Since you are using a wrapper, I think you don't need to explain the register details here.
> + ret = __tdcall_ret(TDX_SYS_RD, &args);
> + /*
> + * The TDCALL TDG.SYS.RD originates from TDX version 1.5.
> + * Treat TDCALL_INVALID_OPERAND error as TDX version 1.0.
> + * If other errors occur, return with zero td_sys.
> + */
> + if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
> + goto version_1_0;
> + else if (ret)
> + return;
> +
> + td_sys->vendor_id = (u32)args.r8;
> +
> + args.rdx = TDX_SYS_MAJOR_FID;
> + __tdcall_ret(TDX_SYS_RD, &args);
Why not check the return value?
> +
> + td_sys->major_version = (u16)args.r8;
> +
> + args.rdx = TDX_SYS_MINOR_FID;
> + __tdcall_ret(TDX_SYS_RD, &args);
Same as above.
> +
> + td_sys->minor_version = (u16)args.r8;
I recommend updating td_sys after executing both TDCALLs.
> +
> + return;
> +
> + /* 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;
> +}
> +
> void __init tdx_early_init(void)
> {
> struct tdx_module_args args = {
> @@ -808,6 +880,7 @@ 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]);
>
> @@ -867,5 +940,9 @@ void __init tdx_early_init(void)
> */
> x86_cpuinit.parallel_bringup = false;
>
> - pr_info("Guest detected\n");
> + tdg_get_sysinfo(&td_sys_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 f74695dea217..d326509832e6 100644
> --- a/arch/x86/include/asm/shared/tdx.h
> +++ b/arch/x86/include/asm/shared/tdx.h
> @@ -17,6 +17,7 @@
> #define TDG_MR_REPORT 4
> #define TDG_MEM_PAGE_ACCEPT 6
> #define TDG_VM_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
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