Exception from QEMU side is not ever checked

[BugraEryilmaz]

Description
The return value of qflex_step is wrong and also not ever used by flexus. The raised variable in the commit function (in CoreImpl.cpp) is always 0.

Steps to Reproduce
Run the timing model with any workload.

Expected Behavior
THe simulation proceeds normally.

Actual Behavior
QEMU cannot inform flexus about any exception it encounters.

Fix
When QEMU experiences an exception or an interrupt, the qflex_step function should return the correct exception code to flexus without further trying to execute any instruction, complying with the flow of flexus. Otherwise, qflex_step should return no exception. The return value should then be used to compare against the exception code calculated by flexus.
Flexus fix commit: 9f80df88, QEMU fix commit: 5a0e88ff.

[BugraEryilmaz]

93bac2cba361bd430d52029653285814a38e2d62 Should fix the issue

[branylagaffe]

The commit does not look like it actually process the exception, merely checking that QEMU and Flexus agreed.

[branylagaffe]

Worth checking RISC-V version

flexus/components/uArch/microArch.cpp

Line 311 in 8da1d20

eExceptionType interrupt =

Interrupt may not be handled correctly

[ayanchak1508]

96acf10e466d632e310830c6b42279123c341247 handles exceptions/interrupts in QEMU the same way its done for RISCV

[branylagaffe]

Use microbench to test the behaviour and coverage of the proposed modification