acpi: AArch64: Enable PSCI in FADT

This commit enables the PSCI (Power State Coordination Interface)
for the AArch64 platform, which allows the VMM to manage the power
status of the guest. Also, multiple vCPUs can be brought up using
PSCI.

Signed-off-by: Henry Wang <Henry.Wang@arm.com>

vmm/src/acpi.rs

@@ -145,6 +145,11 @@ fn create_facp_table(dsdt_offset: GuestAddress) -> Sdt {
         facp.write(256, GenericAddress::io_port_address::<u8>(0x3c0));
     }
 
+    // aarch64 specific fields
+    #[cfg(target_arch = "aarch64")]
+    // ARM_BOOT_ARCH: enable PSCI with HVC enable-method
+    facp.write(129, 3u16);
+
     // Architecture common fields
     // HW_REDUCED_ACPI, RESET_REG_SUP, TMR_VAL_EXT
     let fadt_flags: u32 = 1 << 20 | 1 << 10 | 1 << 8;