Qemu and ARM secure state.

[Jean-Christophe DUBOIS]

Hi,

I have a little application that is designed to work on the i.MX6UL processor.

I developed it and tested it on the mcimx6ul-evk platform emulated by Qemu.

This application used to work "flawlessly" on Qemu 5.0.50 and is working on Qemu 6.0.0 (available as a pre-built package on the latest Ubuntu).

But when I try to run the exact same command line on a Qemu version I compile myself from main/latest of github (Qemu 6.1.50), my application fails to start.

So a little background:

My application expects to start in "secure" state and supervisor mode (which is the default state of i.MX6UL when booting barebone [without u-boot]).

From this state the application tries to get to "non secure" / hypervisor mode which imply going to the "secure" / monitor state before being able to drop to "non secure" / hypervisor. To do so is runs a "smc 0" operand (from "secure" / supervisor).

This "smc" instruction is processed "as expected" by Qemu 5.0.50 and Qemu 6.0.0 (getting to "secure" / monitor mode) but on Qemu 6.1.50 (latest from github) it is as if the smc operand was a no-op. It doesn't trigger any exception and the processor just get to the next instruction after the "smc" instruction. So I am a bit puzzled.

• Is there something that changed in Qemu (since Qemu 6.0.0) when it comes to the "secure" world/state?
• Is there some additional command line parameters to use (I search in the documentation but without luck) to get secure world behavior ?
• Is it necessary to "adapt" the emulated platform (i.MX6UL/mcimx6ul-evk) in some way (it looks like the "virt" machine with "secure=on" does work for arm platform)?

Thanks for your help.

JC