Re: [PATCH v4 00/16] Initial Prefixed Instruction support

On Mon, Mar 23, 2020 at 5:22 PM Nicholas Piggin [off-list ref] wrote:

Jordan Niethe's on March 20, 2020 3:17 pm:

quoted

A future revision of the ISA will introduce prefixed instructions. A
prefixed instruction is composed of a 4-byte prefix followed by a
4-byte suffix.

All prefixes have the major opcode 1. A prefix will never be a valid
word instruction. A suffix may be an existing word instruction or a
new instruction.

This series enables prefixed instructions and extends the instruction
emulation to support them. Then the places where prefixed instructions
might need to be emulated are updated.

The series is based on top of:
https://patchwork.ozlabs.org/patch/1232619/ as this will effect
kprobes.

v4 is based on feedback from Nick Piggins, Christophe Leroy and Daniel Axtens.
The major changes:
    - Move xmon breakpoints from data section to text section
    - Introduce a data type for instructions on powerpc

Thanks for doing this, looks like a lot of work, I hope it works out :)

Yes it did end up touching a lot of places. I started thinking that
that maybe it would be simpler to just use a u64 instead of the struct
for  instructions.
If we always keep the word instruction / prefix in the lower bytes,
all of the current masking should still work and we can use operators
again instead of ppc_inst_equal(), etc.
It also makes printing easier. We could just #define INST_FMT %llx or
#define INST_FMT %x on powerpc32 and use that for printing out
instructions.

Thanks,
Nick