readme: minor fixes

Author: cirosantilli

README.adoc

@@ -2869,7 +2869,7 @@ cd linux-kernel-module-cheat
 sudo ./setup -y
 ....
 
-and then proceed exactly as in <<prebiult>>.
+and then proceed exactly as in <<prebuilt>>.
 
 We don't want to build the full Buildroot image inside the VM as that would be way too slow, thus the recommendation for the prebuilt setup.
 
@@ -8538,7 +8538,7 @@ but the approximation is reasonable.
 +
 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 `fs.py` can enable EL3 with `-V` and EL2 with `--enable-security-extensions`
+** gem5 ARM at least appears to implement more low level CPU functionality than QEMU, e.g. QEMU only added EL2 in 2018: https://stackoverflow.com/questions/42824706/qemu-system-aarch64-entering-el1-when-emulating-a53-power-up See also: <<arm-exception-level>>
 * disadvantage of gem5: slower than QEMU, see: <<benchmark-linux-kernel-boot>>
 +
 This implies that the user base is much smaller, since no Android devs.