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SubjectRe: [PATCH v3 03/11] x86/cpufeatures: Add TDX Guest CPU feature
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On 6/19/2021 6:57 AM, Kuppuswamy Sathyanarayanan wrote:
> Add CPU feature detection for Trusted Domain Extensions support. TDX
> feature adds capabilities to keep guest register state and memory
> isolated from hypervisor.
>
> For TDX guest platforms, executing CPUID(eax=0x21, ecx=0) will return
> following values in EAX, EBX, ECX and EDX.
>
> EAX: Maximum sub-leaf number: 0
> EBX/EDX/ECX: Vendor string:
>
> EBX = "Inte"
> EDX = "lTDX"
> ECX = " "
>
> So when above condition is true, set X86_FEATURE_TDX_GUEST feature cap
> bit.
>

...

> +static inline bool cpuid_has_tdx_guest(void)
> +{
> + u32 eax, sig[3];
> +
> + if (cpuid_eax(0) < TDX_CPUID_LEAF_ID)
> + return false;
> +
> + cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[1], &sig[2]);

As change log describes, EBX + EDX + ECX is "IntelTDX ", not EBX +
ECX + EDX. So it should be

cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2], &sig[1]);

Please also correct early_cpuid_has_tdx_guest()

> +
> + return !memcmp("IntelTDX ", sig, 12);
> +}
> +
> +void __init tdx_early_init(void)
> +{
> + if (!cpuid_has_tdx_guest())
> + return;
> +
> + setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
> +
> + pr_info("Guest initialized\n");
> +}
>

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