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

Huang, Kai
2024-03-22T11:20:05Z

On Mon, 2024-02-26 at 00:25 -0800, isaku.yamahata@intel.com 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?

> +};
> +