x86/hyperv/vtl: Use the wakeup mailbox to boot secondary CPUs

The hypervisor is an untrusted entity for TDX guests. It cannot be used
to boot secondary CPUs. The function hv_vtl_wakeup_secondary_cpu() cannot
be used.

Instead, the virtual firmware boots the secondary CPUs and places them in
a state to transfer control to the kernel using the wakeup mailbox. The
firmware enumerates the mailbox via either an ACPI table or a DeviceTree
node.

If the wakeup mailbox is present, the kernel updates the APIC callback
wakeup_secondary_cpu_64() to use it.

Reviewed-by: Dexuan Cui <[email protected]>
Reviewed-by: Michael Kelley <[email protected]>
Signed-off-by: Ricardo Neri <[email protected]>

Author: ricardon

arch/x86/hyperv/hv_vtl.c

@@ -280,7 +280,8 @@ int __init hv_vtl_early_init(void)
 	 * Otherwise, use an enlightened path since SIPI is not
 	 * available for VTL2.
 	 */
-	if (!(hv_isolation_type_snp() && !hyperv_paravisor_present))
+	if (!((hv_isolation_type_snp() || hv_isolation_type_tdx()) &&
+	      !hyperv_paravisor_present))
 		apic_update_callback(wakeup_secondary_cpu_64, hv_vtl_wakeup_secondary_cpu);
 
 	return 0;