gem5: fs.py EL3 and EL2 require enabling with cli options

README.adoc

@@ -7385,7 +7385,7 @@ but the approximation is reasonable.
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 It is used mostly for microarchitecture research purposes: when you are making a new chip technology, you don't really need to specialize enormously to an existing microarchitecture, but rather develop something that will work with a wide range of future architectures.
 ** runs are deterministic by default, unlike QEMU which has a special <<qemu-record-and-replay>> mode, that requires first playing the content once and then replaying
-** gem5 ARM at least appears to implement more low level CPU functionality than QEMU, e.g. QEMU only added EL2 in 2018, and EL3 is yet unimplemented: https://stackoverflow.com/questions/42824706/qemu-system-aarch64-entering-el1-when-emulating-a53-power-up
+** gem5 ARM at least appears to implement more low level CPU functionality than QEMU, e.g. QEMU only added EL2 in 2018, and EL3 is yet unimplemented: https://stackoverflow.com/questions/42824706/qemu-system-aarch64-entering-el1-when-emulating-a53-power-up gem5 `fs.py` can enable EL3 with `-V` and EL2 with `--enable-security-extensions`
 * disadvantage of gem5: slower than QEMU, see: <<benchmark-linux-kernel-boot>>
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 This implies that the user base is much smaller, since no Android devs.