Hi Pedro,
As you correctly stated, you could make an instruction work in KVM mode by
implementing them as pseudo instruction and using the memory mapped
implementation (m5 –addr).
If you run your instruction in KVM mode, the host won’t recognize the
instruction and your guest VM will get an Undefined Instruction exception.
As from what I am understanding you are using KVM to simply fast-forward
simulation, is there a specific need to run your instruction in KVM mode? Can’t
you just fast-forward simulation until the ROI and then switch over a fully
emulated cpu model (like O3) so that you can simulate the custom instruction in
all its timing details?
Kind Regards
Giacomo
From: Pedro Becker via gem5-users <gem5-users@gem5.org>
Date: Friday, 26 November 2021 at 12:20
To: gem5-users@gem5.org <gem5-users@gem5.org>
Cc: Pedro Becker <pe...@ac.upc.edu>
Subject: [gem5-users] Re: Decisions when adding new instructions: accuracy and
kvm support
Just to partially answer my own question 2.
I just realized that M5 ops are pseudo instructions and they work with KVM
("_addr" version), so I guess I could manage to do the same with my own
instructions, if I was to implement them as pseudo-instructions.
I still don't know if there is a way to make them work with KVM if they are
implemented as custom ISA extensions.
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