Re: [PATCH v19 039/130] KVM: TDX: initialize VM with TDX specific parameters

[Huang, Kai]

On Mon, 2024-02-26 at 00:25 -0800, isaku.yamahata@xxxxxxxxx wrote:
> +struct kvm_tdx_init_vm {
> +	__u64 attributes;
> +	__u64 mrconfigid[6];	/* sha384 digest */
> +	__u64 mrowner[6];	/* sha384 digest */
> +	__u64 mrownerconfig[6];	/* sha384 digest */
> +	/*
> +	 * For future extensibility to make sizeof(struct kvm_tdx_init_vm) = 8KB.
> +	 * This should be enough given sizeof(TD_PARAMS) = 1024.
> +	 * 8KB was chosen given because
> +	 * sizeof(struct kvm_cpuid_entry2) * KVM_MAX_CPUID_ENTRIES(=256) = 8KB.
> +	 */
> +	__u64 reserved[1004];

This is insane.

You said you want to reserve 8K for CPUID entries, but how can these 1004 * 8
bytes be used for CPUID entries since ...

> +
> +	/*
> +	 * Call KVM_TDX_INIT_VM before vcpu creation, thus before
> +	 * KVM_SET_CPUID2.
> +	 * This configuration supersedes KVM_SET_CPUID2s for VCPUs because the
> +	 * TDX module directly virtualizes those CPUIDs without VMM.  The user
> +	 * space VMM, e.g. qemu, should make KVM_SET_CPUID2 consistent with
> +	 * those values.  If it doesn't, KVM may have wrong idea of vCPUIDs of
> +	 * the guest, and KVM may wrongly emulate CPUIDs or MSRs that the TDX
> +	 * module doesn't virtualize.
> +	 */
> +	struct kvm_cpuid2 cpuid;

... they are actually placed right after here?

> +};
> +