Re: [PATCH v3 1/4] KVM: TDX: Track configurable CPUID bits allowed by KVM

[Tony Lindgren]

On Thu, Aug 27, 2026 at 11:18:34AM +0800, Binbin Wu wrote:
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -52,6 +52,149 @@
>  	__TDX_BUG_ON(__err, #__fn, __kvm, ", " #a1 " 0x%llx, " #a2 ", 0x%llx, " #a3 " 0x%llx", \
>  		     a1, a2, a3)
>  
> +static u32 tdx_cpu_cfg_caps[NR_KVM_CPU_CAPS] __ro_after_init;
> +static_assert(ARRAY_SIZE(tdx_cpu_cfg_caps) == ARRAY_SIZE(kvm_cpu_caps));
> +
> +#define TDX_VALIDATE_CPU_CAP_USAGE(name)			\
> +	BUILD_BUG_ON(__feature_leaf(X86_FEATURE_##name) !=	\
> +		     tdx_cpu_cap_init_in_progress)
> +
> +/* For feature bit that KVM advertised through kvm_cpu_caps[]. */
> +#define TDX_CFG_F(name)					\
> +({							\
> +	TDX_VALIDATE_CPU_CAP_USAGE(name);		\
> +	tdx_cfg_caps |= feature_bit(name);		\
> +})
> +
> +/*
> + * For feature bit KVM allows for TDX guests even though it is not advertised
> + * through kvm_cpu_caps[], e.g. MWAIT.
> + */
> +#define TDX_CFG_EXTRA_F(name)				\
> +({							\
> +	TDX_VALIDATE_CPU_CAP_USAGE(name);		\
> +	tdx_cfg_extra_caps |= feature_bit(name);	\
> +})
> +
> +#define tdx_cpu_cfg_cap_init(leaf, feature_initializers...)		\
> +do {									\
> +	const u32 __maybe_unused tdx_cpu_cap_init_in_progress = leaf;	\
> +	u32 tdx_cfg_extra_caps = 0;					\
> +	u32 tdx_cfg_caps = 0;						\
> +									\
> +	feature_initializers						\
> +	tdx_cpu_cfg_caps[leaf] = (tdx_cfg_caps & kvm_cpu_caps[leaf]) |	\
> +				 tdx_cfg_extra_caps;			\
> +} while (0)

How about make some of the above into just static functions for easier
readabilyt?

And then drop the __maybe_unused for tdx_cpu_cap_init_in_progress?