ARM/aarch64: match minimal `i8042` emulation done on x86_64

[acatangiu]

Firecracker does not have an i8042 device on aarch64. We could add the same level of emulation we do on x86_64 that supports:

• the cpu reset event
• emulating Ctrl+Alt+Del keys combo

[pyrito]

Hi, can @mi-yu and I go ahead and get assigned to this issue?

[mi-yu]

To follow up, do you have more specifics on how to go about the emulation for aarch64? I'm looking at the code here: https://github.com/firecracker-microvm/firecracker/blob/master/devices/src/legacy/i8042.rs but I'm not sure what is x64 specific.

[dianpopa]

Hi @mi-yu ,
The i8042 is a keyboard driver that is x86 specific (you cannot enable it for a arm64 kernel config). You can try do a make menuconfig inside a linux kernel on an arm64 and x86_64 machine in parallel. If you go to "Device drivers -> input device support -> hardware i/o ports" you will see that on the x86_64 you get the "i8042 PC keyboard controller" option while on the arm64 machine you do not.
What we could do for arm64 in this scenario is to implement an GPIO controller which is used in virtualized ARM systems to provide injection of keycodes through the linux gpio-keys driver without the need for a more complex device (i.e. a keyboard controller).
We could use the gpio device to send a combination of CTRL+ALT+DELETE, just like we do on x86_64 by implementing the i8042.
Fortunately enough, the linux kernel offers support for the ARM PrimeCell GPIO (PL061) which is a AMBA (Advanced Microcontroller Bus Architecture) compliant device. In Firecracker we already have the RTC which is also an AMBA device implementing the PL031 specification.
So the next step here as far as introducing ctrl-alt-del functionality on aarch64 would be to try to implement the pl061 specification. Take a look at the RTC implementation (devices->src->legacy) for a little bit of inspiration.

[acatangiu]

@mi-yu @pyrito are you still interested in contributing here?

[pyrito]

@acatangiu apologies for the late response. I don't think I will have the time to contribute to this issue in the near future. I'll unassign myself. Thanks!