#!/usr/bin/env python3

# Use the external cpuid program (which must already be installed) to
# determine the maximum amount of Enclave Page Cache (EPC) supported by
# the system.  This value is often configurable in your BIOS, but not at
# runtime.

import re
import subprocess
import sys

def get_max_epc_bytes():
    max_epc_bytes = 0
    subleaf = 2
    while True:
        ret = subprocess.run(["cpuid", "-1", "-l", "0x12", "-s",
                str(subleaf)], capture_output=True)
        if ret.returncode != 0:
            print("Unable to run cpuid", file=sys.stderr)
            sys.exit(1)
        match = re.search(r'section size\s*=\s*0x([0-9a-fA-F]+)',
            str(ret.stdout))
        if match is None:
            break
        max_epc_bytes += int(match.group(1), 16)
        subleaf += 1

    return max_epc_bytes


if __name__ == "__main__":
    max_epc_bytes = get_max_epc_bytes()
    print("Max EPC available:",
        format(max_epc_bytes / (1<<30), ".2f"), "GiB")